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1. ha Empty Project a VI from Temeate Pia Tierra adc i AOS Any te PL wil Precio ae ori Gearree abbr Aa Drei opine wl FAUT ask wi Ore Tima Step vi Wok Tortosict wi Baar rae vi Pariz Purediarreerit abs wi SERRE RET Iii Function Germerstor wth Po G i i 4 Lable Student Edition Pie To La AF Getting Sharted wath Lab IEW LabWwWIE 4 Purmdement ale Guide to Lab EW Documentetion LabwE WW Help Upgrading Lab EYF MathScript 30 Picture Cornirol LabwEW Object Oriented Proagranunding List of Al eww Fasbunreg Web Resources DiecLisciom Ferie Trairi Cores Leb JEW Scere Lranmples d E Pind Examples Figure 3 2 LabVIEW Getting started window You will begin with simply clicking on the blank VI once you click two windows appear The first window is the front panel behind it is the block diagram On the front panel when you click the mouse right button the control pallet will be brought up so we can access the available controls and indicators These include numeric objects such as gauges and knobs Boolean indicators such as buttons in different types text controls and indicators graphs charts arrays tables clusters and more On the Block diagram where you develop your codes clicking on the mouse right button makes the access to the function pallet where all the LabVIEW functions found These include structures for while loop and for loop functions for simple math arrays B
2. Figure 4 3 a knobes Figure4 3 b Elvis II right side 4 1 3 NI ELVIS II Series Prototyping Board This section describes the NI ELVIS II Series Prototyping Board and how to use it to connect circuits to NI ELVIS II The NI ELVIS II Series Prototyping Board connects to the 35 bench top workstation The prototyping board provides an area for building electronic circuitry and has the necessary connections to access signals for common applications Figure 4 4 shows the prototyping board with a brief description You can use multiple prototyping boards interchangeably with the NI ELVIS H Bench top Workstation Removing it from the bench top workstation You can use the prototyping board connector to install custom prototype boards you develop This connector 1s mechanically the same as a standard PCI connector Al and PFI Signal Rows T DMM AO Function Generator Benchtop Workstation Interface Connector User Configurable VO Variable Power Supplies DIO Signal Rows and DC Power Supplies Signal Rows User Configurable LEDs 8 DC Power Supply Indicators User Configurable D SUB Connector 9 WUser Configurable Screw Terminals Counter Timer User Configurable I O 10 User Configurable BNC Connectors and DC Power Supply Signal Rows 11 User Configurable Banana Jack Connectors 12 Screw Positions for Locking Figure 4 4 Protyping Board Description 4 1 4 NI ELVIS Functions NI ELVIS II performs functions similar to a number of real instruments w
3. gt a OTERMIN TERMINALS x Figure 3 5 Input and output functions terminals You can run the VI from the front panel either the block diagram by clicking the run white arrow on the tool bar which will be changed to the black arrow as following 5 Errors in LabView are shown up without necessary to run the program for example 1f you wire to terminals have different types it will show the run wire as a broken wire If you did something in the right way you will see a check mark on the tool bar If there other mistakes such as unwired terminal the run arrow will be converted to a broken arrow If you click on the broken arrow you can see window that include a brief description about the errors as in Figure 3 6 Clicking on the Show Errors button locates the errors position An Interesting feature in the LabVIEW programming language that there is a possibility to follow the program logically in the case that you want to see how the VI works or to look out for logical errors This can be achieved by running the VI under highlight execution EIE It allows you to see how exactly the data flow from terminal to terminal with numbers evaluation at each node and each loop iteration 26 2 errors and warnings amp Block Diagram Errors Subtract Subtract contains unwired or bad terminal Wire has loose ends Details One or more required inputs to this Function are not wired or are wired incorrectly Show the Context He
4. may be needed for applications such as magnets motors and electronic components The HTSC are ceramics and have all the brittleness problems associated with non superconducting ceramics In addition Jc is not an intrinsic property of superconductors but is a function of the processing procedure The rare earth superconductors also have highly directional properties Therefore a crucial problem is to fabricate the material into a useful shape and still have sufficiently high Jc and mechanical strength for practical applications The field of electronics holds great promise for practical applications of superconductors The miniaturization and increased speed of computer chips are limited by the generation of heat and the charging time of capacitors due to the resistance of the interconnecting metal films The use of new superconductive films may result in more densely packed chips which could transmit information more rapidly by several orders of magnitude Superconducting electronics have achieved impressive accomplishments in the field of digital electronics Logic delays of 13 picoseconds and switching times of 9 picoseconds have been experimentally demonstrated Through the use of basic Josephson Junctions scientists are able to make very sensitive microwave detectors magnetometers SQUIDs and very stable voltage sources 12 12 The use of superconductors for transportation has already been established using liquid helium as a refri
5. ATN Attention GND 11 Ground Wire Twisted pai SHIELD Cable Shield Logic Ground 4 3 2 Types of Messages Devices on the GPIB communicate by passing messages through the interface system There are two types of messages e Device dependent messages often called data or data messages contain device specific information such as _ programming instructions measurement results machine status and data files e Interface messages manage the bus itself They are usually called commands or command messages Interface messages perform such functions as initializing the bus addressing and unaddressing devices and setting devices for remote or local programming 21 The term command as used here should not be confused with some device instructions which are also call commands Such device specific instructions are actually data Messages 4 3 3 Talkers Listeners and Controllers There are three types of GPIB communicators A Talker sends data messages to one or more Listeners The Controller manages the flow of information on the GPIB by sending commands to all devices 43 Devices can be Talkers Listeners and or Controllers A digital multimeter for example 1s a Talker and may also be a Listener A printer or plotter is usually only a Listener 4 3 4 Restrictions To achieve the high data transfer rate that the GPIB is designed for the physical distance between devices and the number of devices on the bus is
6. RS 485 and data acquisition control vision and motion control devices LabVIEW also has built in features for connecting your application to the Internet using the LabVIEW Web server and software standards such as TCP IP networking and ActiveX Using LabVIEW you can create 32 bit compiled applications that give you the fast execution speeds for custom data acquisition test and control solutions You also can create stand alone executables and shared libraries like DLLS because LabVIEW is a true 32 bit compiler LABVIEW contains comprehensive libraries for data collection analysis presentation and storage It also includes traditional program development tools You can set breakpoints animate program execution and single step through the program to make debugging and development easier LABVIEW also provides numerous mechanisms for connecting to external code or software through DLLS shared libraries ActiveX and more In addition numerous add on tools are available for a Variety of application needs 22 3 2 LabVIEW Program LabVIEW programs are called virtual instruments or VIs because their appearance and operation imitate physical instruments such as oscilloscopes and multimeters Every VI uses functions that manipulate input from the user interface or other sources and display that information or move it to other files or other computers A VI contains the following three components 21 e Front panel Serves as the user int
7. cutting tools cleaning agents Ag paste Figure 5 1 Photo for the I V characteristic and resistivity measurement system LN Fill funnel sample space valve LN vent racuum space valve sample tube I al filled with ve He gas _ probe stick vacuum space sample electromagnet Figure 5 2 Cryostat for making low temperature measurements in an external magnetic field 5 2 The Linear Four Probe Method The resistivity of the superconductor is often determined using a four point probe technique With a four probe or Kelvin technique two of the probes are used to source current and the other two probes are used to measure voltage Using four probes eliminates measurement errors due to the probe resistance the spreading resistance under each probe and the contact resistance between each metal probe and the semiconductor material Because a high impedance voltmeter draws little current the voltage drops across the probe resistance spreading resistance and contact resistance are very small 54 The most common way of measuring the resistivity of a superconductor material is by using a four point collinear probe This technique involves bringing four equally spaced probes in contact with a material of unknown resistance The probe array is placed in the center of the material as shown in Figure 5 3 Bulk State a b Figure 5 3 a Macro and b micro four point probe m
8. 12 V on the SUPPLY terminal and 0 to 12 V on the SUPPLY terminal All power supplies on NI ELVIS I are referenced to GROUND 5 Bode Analyzer The Bode Analyzer uses the Function Generator to output a stimulus and then uses analog input channels AI 0 and AI 1 to measure the response and stimulus respectively 37 4 2 NI ELVIS Band Pass Filter In circuit theory a filter is an electrical network that alters the amplitude and or phase characteristics of a signal with respect to frequency Ideally a filter will not add new frequencies to the input signal nor will it change the component frequencies of that signal but it will change the relative amplitudes of the various frequency components and or their phase relationships Filters are often used in electronic systems to emphasize signals in certain frequency ranges and reject signals in other frequency ranges Such a filter has a gain which is dependent on signal frequency There are five basic filter types bandpass notch low pass high pass and all pass The filter used in this section as an example of bandpass filters The number of possible bandpass response characteristics is infinite but they all share the same basic form 23 There are applications where a particular band or spread or frequencies need to be filtered from a wider range of mixed signals Filter circuits can be designed to accomplish this task by combining the properties of low pass and high pass into a sin
9. I Huang Gorman G savoy and Beyers R Bulk Superconductivity at 125 K in TloCa Ba Cu30 APS Physics 1988 60 2539 2542 94 17 20 21 22 29 24 25 26 27 28 29 30 3 p Chu C W Gao L Chen F Huang Z J Meng R L and Xue Y Y Superconductivity above 150 K in HgBazCa2Cu 0s x at high pressures Nature 1993 365 323 325 Ulrich H Winenand The SSC Low Eneregy Booster place IEEE Prss 1997 0 7803 1164 7 Ohanian H Markert J physics for engineers and scientists gt ed New yourk W W Norton amp company Inc 2007 689 978 0 393 93003 0 Kenning G G Rodriguez R Zotev V S Moslemi A Wilson S Hawel L Detection of magnetically enhanced cancer tumors using SQUID magnetometry A Feasibility Study Instrum 2004 76 1 9 National Instrument Serial Polling and SRQ Servicing with NI 488 2 Software and LabVIEW Aug 1998 6 341560A O1 Rick Bitter Taqi Mohiuddin Matt Nawrock LabVIEW Avanced Programming Techniques hae Eddition Motorola Taylor amp France Group 2007 491 13 0 8493 3325 5 Mavino Albert Paul Electronic Principles Sixth ed Singapore McGraw Hill companies 1999 1002 0 07 115604 6 Dustakar K and Berkowitz S An Ultra narrowband HTS Bandpass Filter IEEE International Microwave Symposium Digest June 2003 3 1881 1884 Keithley Instrument Inc Model 2182 Nanovoltmeter User s Manual c ed Cleveland Ohio U S A 1998 2182 900 01 Hewlett Pack
10. Through the collaborative efforts of government funded research independent research groups and commercial industries applications of new high temperature superconductors will be in the not so distant future Time lags however between new discoveries and practical applications are often great The discovery of the laser in the early 60 s has only recently been appreciated today through applications such as laser surgery laser optical communication and compact disc players The rapid progress in the field of 13 superconductivity leads one to believe that applications of superconductors are limited only by one s imagination and time As you can see application of superconductors is only just a beginning e Transmission Line Power transmission is loosely defined as the transfer of electric energy from one source to a load over conductors that carry relatively large current with lower Ohmic loss The penalty is the need to keep the superconductor cold Fortunately the superconductor can support a very large current density and so little material is needed for the conductor The Figure below shows superconductor wires where the cables are composed superconducting there is no resistance and very little loss of electricity This transmission cable can carry 3 5 times the current of conventional power cables 19 Figure 2 7 Superconductor wires e Electric Motors The main advantage of using superconductors in electric motors is that th
11. a specific protocol to communicate with the instrument How the computer controls the instrument and acquires data from the instrument depends on the type of the instrument GPIB serial port and PXI are common types of instruments Like general purpose DAQ devices instruments digitize data but they have a special purpose or are designed for a specific type of measurement For standalone instruments you generally cannot modify the software that processes the data and calculates the result because the software usually is built into the instrument Because modular instrumentation uses software running on standard PC technology you can more easily modify the behavior of these instruments For example with some digital multimeter modular instruments you can program the instruments to acquire a buffer of data at a high rate of speed much like an oscilloscope 3 3 5 Examples of Virtual Instruments Vis LabVIEW includes hundreds of example VIs you can use and incorporate into your own VIs You can modify an example to fit your application or you can copy and paste from one or more examples into your own VI 3 5 1 Simple VI Design Patterns When performing calculations or making quick lab measurements you do not need a complicated architecture Your program might consist of a single VI that takes a measurement performs calculations and either displays the results or records them to disk The simple VI design pattern usually does not require a s
12. biomagnetism In the body neurons and muscle fiber both generate current when they are activated SQUID can be used to detect a magnetic signal generated by several neurons or muscle fibers Magnetoencephalgraphy MEG is using SQUID technology to produce a map of brain s magnetic activity which can be used for tumor diagnosis 20 Superconductor Contacts p Pa Noyer s Insulator Figure 2 10 SQUID SNS Junction 18 e High Temperature Superconductor Filters Microwave resonators with extremely high quality factors result in the ability to make filters with very little insertion loss even with multiple poles in the filter or even when the filter bandwidth is extraordinarily narrow When such filters are used in receiver front ends it is possible to have maximum frequency selectivity and maximum receiver sensitivity at the same time Conventional filter technologies sacrifice sensitivity when selectivity is increased In contrast filters made using superconductors provide the closest approximation to a perfect filter namely one that allows 100 percent of the desired signals to pass through and rejects 100 percent of the unwanted signals Figure 2 11 Hence such filters are ideally suited for rejecting out of band signals particularly those that are very close in frequency to the desired band Because of the unique properties of superconducting filters the most appropriate applications for the technology are either to
13. during current flow So the biggest challenge is to record the data in a calibrated time where you are sure that all measurements are taken under the same temperature To manage the whole process with suitable time and high efficiency we suggested interfacing the system through GPIB USB with computer using LabVIEW as a programming language A special program was created for this system by merging the two devices into one and complete program where one can control the temperature sweep I measure V and plotting I V curves Figure 5 11 shows the front panel of tempe Controller with I V sweep VI 68 In the Lakeshore 331S part one can set your PID values specify the temperature set point the time to wait between each record and the heater range mode As you run the VI the new setting takes place the current sensor temperature is displayed in the Temp K indicator At the same time temperature versus current is being plotted and tabulated to LabVIEW at real time so you can see the variation in temperature with time at the same time you can judge weather the temperature 1s stable see the history of temperature cooling or warming and estimate the time that you need to reach the stable state At the end of the process the program automatically save a copy of data to an excel file In figure 5 11 the second Part for Kethiley 2425 you can set the start and stop current values for the current sweep You can choose the number of points o
14. library a single interface library for controlling GPIB VXI RS 232 and other types of instruments Drivers using VISA are scalable across instrument I O interfaces 3 8 Data Acquisition This section describes you how to use LabVIEW with general purpose data acquisition DAQ hardware If you use only stand alone instruments and control them with GPIB VXI or serial standards refer to the Instrument I O section of this chapter Use the DAQ Solution Wizard If you are using DAQ hardware you must configure analog input analog output digital input or digital output channels You can launch the DAQ Channel Wizard from the DAQ Solution Wizard to configure the channels Then you can generate a DAQ solution from the Solutions Gallery 22 Configure Analog Input Channels The DAQ Solution Wizard guides you through naming and configuring analog and digital channels using the DAQ Channel Wizard The DAQ Channel Wizard helps you define the physical quantities you are measuring or generating on each DAQ hardware channel It queries for information about the physical quantity being measured the sensor or actuator being used and the associated DAQ hardware 32 Chapter Four Selected Examples on Interfacing Using Lab VIEW 4 1 NI ELVIS I The National Instruments Educational Laboratory Virtual Instrumentation Suite II NI ELVIS II is a LabVIEW and computer based design and prototyping environment NI ELVIS II consists of accustom design
15. limited The following restrictions are typical A maximum separation of four meters between any two devices and an average separation of two meters over the entire bus maximum total cable length of 20 meters No more than 15 devices connected to each bus with at with at at least two thirds powered on 25 4 4 LF Impedence Analyzer Automated HP 4192A impedance material analyzer with a homemade LabVIEW program provides a total solution for high accuracy and easy measurement of surface mount components and dielectric magnetic materials It performs both network and impedance analysis Basic impedance accuracy is 0 15 High Q accuracy enables low loss component analysis on such devices as telecommunication filters audio video electronic circuits and basic electronic components 26 The HP 4192A impedance analyzer measures electrical impedance phase angle resistance conductance inductance capacitance and dissipation factor Primary use in our lab is for characterizing dielectric properties of polymers An internal synthesizer sweeps frequency from 5 Hz to 13 MHz with 1 mHz resolution A long cable connects the analyzer to a test station you can extend your test point away from the analyzer without losing accuracy HP 4192A is a fully automatic high performance test instrument designed to measure a wide range of impedance parameters as well as gain phase and group delay This instrument mainly used in our lab to investigate electrical impe
16. now probably know more experimentally about this class of materials than any other we still have so many unresolved issues in understanding the basic mechanisms of high temperature superconductivity 10 pie ease eid im 30 GPa TIBaCaCud o HgTIBaCacCuo pisrcacuc HgbBatCaCud k a YBalu Might on tia ee 7 Ligqued mbrogen DSC a ra 1 4GPa MoB LaBaCud o Nyce BBO o Nb gt WS Keo Li 33 GPa ACHT SL Surtees ol Piluti Liigus Temperature Kelvin i Liguid hydine er CAT P Pu ias Cac Als CeColn p Liquid ES a im a 1300 1940 1990 1995 2 OO 2010 Year Figure 2 6 Superconductor evolution through since 1900 2 2 Applications of Superconductivity The phenomenon of superconductivity is having a tremendous impact on the advancement of technology in many fields including medicine and electronics It is expected to have more impact in the future of electric motors power production and transmission transportation and communication systems Accordingly the call to develop superconducting materials is strong and will remain so as the technology improves and becomes less expensive Discovering or developing a material which becomes superconducting at room temperature is the ultimate challenge in superconductivity But with the uncertainty of this ever being achieved the current focus of much of the research development and commercialization of superconducto
17. such as user actions I O triggers and so on the main application phase gets more complicated 3 6 Parallelism Parallelism is a way to execute multiple tasks at the same time To discuss parallelism consider the example of creating and displaying two sine waves at different frequencies You place one sine wave in a loop and the second sine wave in a different loop A challenge in programming parallel tasks is passing data among multiple loops without creating a data dependency For example if you pass the data using a wire the loops are no longer parallel In the multiple sine wave example you may want to share a single stop button between the loops as shown in Figure 3 8 Some applications require the program to respond to and run several tasks concurrently One way of designing the main section of this application is to assign a different loop to each task For example you might have a different loop for each button on the front panel and for every other kind of task such as a menu selection I O trigger and so on Figure 3 9 shows this parallel loop design pattern 30 Chart 1 Chart 2 Plot o B Loop Control i OFF b On Amplitude Amplitude Figure 3 8 Parallel Loops front panel Skart Up vi Shut Gown vi Merge Errors wi oom ia he Process 1 Code Here 7 Process 2 Code Here mHE A a Figure 3 9 Parallel Loop Design Pattern This structure is straightforward an
18. superconducting state with respect to magnetic field temperature and current density Type I and type II superconductors Magnetic levitation force YBCO Structure Superconductor evolution through since 1900 Superconductor wires High temperature superconducting electric motors The Yamanashi MLX01 MagLev train SQUID SNS Junction Wideband high Tc superconductor filter measured data Tools Controls and function pallets LabVIEW Getting started window The front panel for addition amp subtraction VI The block diagram for addition amp subtraction VI Input and output functions terminals LabVIEW Error list window Simple VI Architecture General VI Design Pattern Parallel Loops front panel Parallel Loop Design Pattern NI EIVIS II hard ware NI ELVIS II Soft Panel Knobes Elvis II right side Protyping board Description block diagram for band bass filter Figure a The electronic circuit for the banpass filter b Amplitude and phase response curves for example bandpass filter Note symmetry of curves with log frequency and gain scales GPIB CARD GPIB USB HS GPIB Cable Connecetor HP 4192A computer interface Home page of hp4192A Calibration page Run amp Acquire data front panel and part block diagram Analyzed Data page and part of its block diagram Flow chart for hp 4192A program Photo for the I V characteristic and resistivity measurement system Cryostat for making low temperature
19. the material These circulating currents could not be sustained in a material of any finite electrical resistance Figure 2 4 Magnetic levitation force These circulating persistent currents form an array of electromagnets that are always aligned in such as way as to oppose the external magnetic field In fact a mirror image of the magnet is formed in the superconductor with a north pole below a north pole or a south pole below a south pole If the magnet is moved or rotated the mirror image of the magnet rotates with it A disk magnet levitating over a superconductor may be spun rapidly about its longitudinal axis without affecting its levitation Figure 2 4 shows that diamagnetism is strong enough to levitate a magnet can only occur in a superconductor For this reason the levitating magnet test is one of the most accurate methods of confirming superconductivity In 1950 Emanual Maxwell discovered the isotope effect in superconductors 11 This experimental observation was an important key to the theoretical explanations of the mechanism of superconductivity In the isotope effect the critical temperature for many superconductors depends on the isotopic mass indicating that lattice vibrations are involved in the superconductivity and that the attractive coupling between electrons is through the lattice vibrations 1 e phonon mediated Thus the existence of isotope effect indicated that although superconductivity is an el
20. this property The critical temperature Tc varies from superconductor to superconductor but lies between less than 1 K and approximately 20 K for metals and metallic alloys Recently it has been demonstrated that some complex cuprate oxide ceramics have Tc in excess of 100 K 9 The transition from the normal to the superconducting state phase is often sharp and the sharpness of superconducting state transition depends on the state and purity of the sample but in favourable situations it can occur within a temperature interval of less than 0 001 K The resistivity temperature behaviour for superconductive and non superconductive materials is shown in Figure 2 1 Zero resistance of a superconductor implied transmission of current at any distance with no losses the production of large magnetic fields because a superconducting loop could carry current indefinitely storage of energy These applications were not realized because as was quickly discovered the superconductors reverted to normal conductors at a relatively low current density Jc or in a relatively low magnetic field called the critical field Bc The three material parameters Tc Bc and Jc have become very important in the practical applications of superconductivity Hon superconductive Metal x Ea ad w Gee Superconductor ay 0 RE Tempe e rature i Figure 2 1 Temperature dependence of the resistance for normal and superconducting states Figure 2 2 show
21. with a magnet allowing the observation of both phenomena In such case levitation or free suspension of a superconducting body occurs with respect to the source of a non uniform magnetic field These phenomena are both of academic and technological concern From the point of view of possible applications levitation of a superconductor above a magnet or vice versa is of central interest with regard to the commercialization of HTS Indeed magnetic levitation involving HTS is considered as a way to support high speed vehicles and some proposals and prototypes of trains levitated by superconducting coils actually exist It also appears possible to use these materials for magnetic bearing applications such as generators energy storage systems and electric motors Having these applications in mind superconductors should be capable to levitate with different objects attached to them and then the interaction force with the magnet should be much higher than the superconductor s weight In this section we will survey the main 76 concepts on the magnetic properties of superconductors that are necessary to understand the context for magnetic levitation involving superconducting materials I Da conductor Super Magnet E om See Balance i Figure 5 15 Levitation experiment set up Measurement of the interaction force between a HTS and a magnet are performed with the apparatus described in Fig 5 15 We use an electrobala
22. 0 5 mm Then the levitation force 1s measured moving the sample at constant speed relative to the magnet The set magnet plate cup loads the balance and this weight is tared to have a null starting reading In these conditions the balance will sense as an extra load the force due to the magnetic interaction between the superconductor and the magnet and the instrument will give positive or negative readings as a signature of the repulsive or attractive character of this interaction The null reading may correspond to the interaction force when 7 the bulk sample 1s in the superconducting state but infinitely away from the magnet ii the total magnetic moment is averaged to zero in the volume of the sample iii the material is at a T gt Tc and displays normal properties We perform data acquisition via a home made RS232 interface of the balance and thus the interaction force weight is directly printed into an excel spreadsheat and saved The samples used are a pure YBCO Tc 93K and a nano Al O3 doped YBCO with cylindrical shape radius 10 mm height 2 mm The doped sample contains nano sized inclusions of non superconducting AlO incorporated to the superconducting matrix during the growing process in order to increase the number of pinning centers which 78 increase the critical current density and thus the pinning force Both samples display hysteretical features related to their magnetic history at liquid nitrogen temperature i
23. 2 NI ELVIS I Soft Panel 4 1 1 Applications NI ELVIS II SFP instruments such as the Bode Analyzer and Dynamic Signal Analyzer offer instructors an opportunity to teach advanced courses in signal analysis and processing 34 Mechanical engineering students can learn sensor and transducer measurements in addition to basic circuit design by building custom signal conditioning Students can install custom sensor adapters on the prototyping board For example installing a thermocouple jack on the prototyping board allows robust thermocouple connections 4 The programmable power supply can provide excitation for strain gauges use in strain measurement Physics students typically learn electronics and circuit design theory NI ELVIS I provides these students with the opportunity to implement these concepts For example physics students can use NI ELVIS II to build signal conditioning circuits for common sensors such as photoelectric multipliers or light detector sensors 4 1 2 NI ELVIS II Bench top Workstation NI ELVIS II hardware contains Bench top Workstation and Series Prototyping Board The workstation control panel provides easy to operate knobs for the variable power supplies and function generator figure 4 3 a and offers convenient connectivity and functionality in the form of BNC and banana style connectors shown in figure 4 3 b to the function generator scope and DMM instruments at the right side of the bench top
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25. STUDYING MAGNETOTRANSPORT PROPERTIES OF SUPERCONDUCTORS USING LABVIEW by Huda Mahmoud Haddad Dr Abdalla Obeidat Dr Borhan A Albiss Thesis submitted in partial fulfillment of the requirements for the degree of M Sc in Physics At The faculty of graduate studies Jordan University of science and Technology June 2010 STUDYING MAGNETOTRANSPORT PROPERTIES OF SUPERCONDUCTORS USING LABVIEW STUDYING MAGNETOTRANSPORT PROPERTIES OF SUPERCONDUCTORS USING LABVIEW by Huda Mahmoud Haddad Signature of Author 2 ec e eee e cece cece ae eee Committee Member Signature and Date Dr Abdalla Ahmed Obiedat Chairman hace ec cee cece cece ees Dr Borhan A Albiss Co Advisor acc e ccc e eee ceeeceeees Dr Maen Gharaibeh Member hae cece cece eee e eee cece Dr Abdul Raouf Al Dairy External Examiner YU on eee eee June 2010 DEDICATION To my Mother To my Brothers and Sisters And To My advisors Dr Abdalla A Obeidat and Dr Borhan A Albiss ACKNOWLEDGMENTS I would like to thank my advisor Dr Abdalla Obeideat for his support and for his supervision during the research I am also indebted to him for his guidance in different fields specially in computational physics and programming and for sharing his knowledge and resources I am grateful to my Co advisor Dr Borhan Albiss for his encouragement and support during the whole research project He is one of the fewest teachers that you will never forget hi
26. Tc decreases a T e far above the opening temperature of liquid nitrogen temperture 77 K is advantageous Moreover the new materials are more stable than the rare earth cuprate superconductors they do not lose oxygen or react with water The maximum value of T has now increased to 133 K for mercury based cuprate Hg Baz Caz Cu3081x When this compound is subjected to high pressure 30 G Pa the onset of T increases to 164 K more than half way to room temperature 17 While Hg Ba2 Ca2 Cu3 Og cannot be used in applications of superconductivity at such high pressures this striking result suggests that values of Tc in the neighborhood of 160 K or even higher are attainable in cuprate oxides at atmospheric pressure Several research groups have claimed even higher transition temperatures but none of them were reproducible or independently confirmed by other laboratories The dramatic evolution of critical temperatures that have been observed since 1911 is illustrated in Figure 2 6 where the maximum value of Tc is plotted versus date YBCO YBaCuO where O lt 6 lt Also abbreviated Y123 Oxygen Copper e Yttrium Barium Figure 2 5 YBCO Structure During the last ten decades high quality polycrystalline single crystal and thin film specimens of these superconducting materials have been prepared and investigated extensively world wide to determine their fundamental normal and superconducting state properties Although we
27. ai ied a a TULL LOL LDR L tobe E rot ted te ted el toh fast Gol ed Mol Ral Gol Mee Ged el Gal tel GoD ot ot God eel fel Go fel ol tel ge i Ty Tee bot toed el Coe tat eal tet Cel Me ol Gol a fen Got al ed T figure 4 12 Run amp Acquire data front panel and part block diagram 49 anlyze ome Yi WTE srs log freq DA Figure 4 13 Analyzed Data page and part of its block diagram 50 hp4192A VI Caliberation Z Angle d R G X B oe O 0 l EE EE Hp4192A Hp4192A Hp 4192A LabVIEW Table Save to XIs file f Function Save to Save analyzed To xls file Save Analyzed data Data to XIs file Figure 4 14 Flow chart for hp 4192A program Chapter Five Experimental Set Up 5 1 Characteristic and Resistivity Measurement The system for I V characteristic and resistivity measurements was build up in our laboratory Figure 5 1 shows a photo for this system as you see it consist of A Cryostat consist of three regions which will be described later the interior region contains the probe stick which consist of six probes two connected between the silicon diode sensor which is connected to the sample holder and heater controller to take the measurements at different temperatures and the other four probes connected between the sample surface and the Source Meter two for voltage and another two probes for current the 4 probe connection shown in Figure 5 4 the samp
28. all the time e Super Fast Computer Chips Superconductor materials can switch from superconducting state to the non superconducting state in 10 sec about 1000 times faster than silicon The suggestion that computers made from superconductors might be 1000 times faster than computers based on silicon chip technology 15 e Levitation Superconducting Magnetic Energy Storage Devices SMES Electric power plants face their peak demand from customers in the late afternoon but have excess generated at night and stored for half a day The power plant would be much more efficient One way to store energy is to make a flywheel s bearings With high temperature superconductors employed as bearings the efficiency of flywheel energy storage can improve dramatically The mechanism behind superconductive flywheel bearing 1s Meissner Effect Superconductor can repel magnetic field and a magnetic material will stand away from a superconductor Therefore it is possible to build a bearing surface with absolute no contact between pieces e Magnetic Levitation Vehicles Main mechanism is Meissner Effect There is attractive force between electromagnets and a ferromagnetic guidway which is called electromagnetic system and there is repulsion force between two parts which is called electrodynamics system Magnetic Levitation Vehicles can reach speeds of over 300 mph Figure 2 9 This method of transportation could be used to connect cities which are
29. ard HP 4192A Lf Impedance Analyzer Operation and Service Manual Jaban 1988 16047 90000 Ahmed H al Ganem H The effect of nano size on the electric conductivity and on the activation energy of Polyaniline prepared electrochemically Jordan Al albayt univ 2004 127 Rawashdeh N Albiss B A Effect of Nonoparticles Addition on High Temperture Superconductors Jordan J U S T January 2009 83 Morgan D V Borad K An Introduction to Semiconductor Microtechnology Britain April 1985 164 0 471 90148 2 Maloof ED User s Manual Model 331S Temperature westervill Ohio LakeShore cryotronics inc 2000 43082 8888 Thomas D Rossing and John R Hull Magnetic Levitation accessed 2010 March Available from URL http hO web u sud fr supraconductivite vulgafichiers magnetLevitationGeneral 95 a2 33 34 aD 36 37 38 39 40 Wei J C Chen J L Horng L Yang T J Magentic force acting on a magnetic dipole over a superconducting thin film Phys Rev B 1996 54 21 High Temperature Superconductivity Advanced Lab Magneto Transport in the normal state accessed 2010 March Avaliable from URL http www physics buffalo edu cerne eduction hts4 pdf Al Khateeb H M Albiss B Alzoubi F Y Al Qadi M K Hasan M K Ayoub N Y Levitation force between monolayer of magnetic particles and superconducting plane in meissner state IEEE Transactions on Applied Superconductivity 2008 18 1 14 16 T H Johan
30. ath state before attaining the normal resistive state of the metal The upper critical field of type II superconductors tends to be two orders of magnitude or more above the critical fields of a type I superconductor Therefore it is the advent of the type II superconductor that has made possible the manufacturing of superconducting magnets of incredible strength We must note that a type I superconductive body as exemplified by many pure metals exhibits perfect diamagnetism Meissner state below Tc and excludes a magnetic field up to some critical field Hc where upon it reverts to the normal state Magnetic field dependence for type I or soft and type II or hard superconductors are shown in Figure 2 3 Current Density J Je Superconducting Region Temperature T ees a He Magnetic Field H Figure 2 2 Illustration of the functional dependence of the superconducting state with respect to magnetic field temperature and current density Type I T j H Ha H Hi Applied magnetic field Bg Applied magnetic field B a b Figure 2 3 Type I and type II superconductors The diamagnetic effect that causes a magnet to levitate above a superconductor is a complex effect Part of it is a consequence of zero resistance and of the fact that a superconductor cannot be shorted out The act of moving a magnet toward a superconductor induces circulating persistent currents in domains in
31. ation April 2008 33 374629A 01 Li S Khan A A Developing Digital Measurement and Analysis Laboratory in Circuits and Electronics Lab Proceedings of the 2004 American Society for Eng Education Annual Conference amp Exposition 2004 TAMUK Bednorz J G and M ller K A Possible High Tc Superconductivity in the Ba La Cu O System Z Phys B 1986 64 189 194 Kammerlingh Onnes H The Superconductivity of Mercury Comm Phys Lab Univ Leiden 1911 122 124 Meissner W and Ochsenfeld W Ein neuer effekt bei eintritt der supraleitfahigkeit Naturwissenschaften Naturwissenschaft 1933 21 44 787 788 Abrikosof A A On the magnetic Properties of superconductors of the Second Group Soviet Physics Jetp 1957 5 1442 1452 Emanuel Maxwell Isotope Effect in the Superconductivity of Mercury Phys Rev 1950 78 477 477 Josephson B D Possible New Effects in Superconducting Tunnelling Phys Rev Lett 1962 1 251 Bardeen Cooper L N and Schrieffer J R Theory of Superconductivity Phys Rev 1957 108 1175 Wu K M Ashburn J R Torng C J Hor P H Meng C Gao L Huang Z H Wang Y Q and Chu C W Superconductivity at 93 K in a new mixed phase Y Ba Cu O compound system at ambient pressure Phys Rev Lett 1987 58 908 910 Schmirgeld L Regnier P Deschannels X and Maurice F Interdiffusion between YBCO and Bi1 based high T superconducting ceramics 1992 32 1000 1004 Parkin S S P Lee V Y Engler E M Nazzal A
32. ble instruments manufactured by them Because of its high system data rate ceilings of from 250Kbytesto 1M byte per second the GPIB quickly became popular in other applications such as inter computer communication and peripheral control It was later accepted as the industry standard IEEE 488 25 The versatility of the system prompted the name General Purpose Interface Bus Figure 3 7 a and b show the GPIB card and GPIB USB HS which are used in our connections 41 4 3 1 GPIB Signals The interface bus consists of 16 signal lines and 8 ground return or shield drain lines The 16 signal lines are divided into three groups 8 data lines 3 handshake lines interface management lines The following figure shows the arrangement of these signals also table 4 1 illustrate pin signals with a brief description for each pin function Figure 4 8 GPIB cable connecetor Table 4 1 GPIB signal description ee e Data Input Output I L DIO 1 Line DIO 5 Data Input Output Line 5 Data Input Output 5 DIO 2 fac ike 14 DIO 6 Data Input Output Line 6 Data Input Output DIO 4 ona Pii ii Data Input Output Line 8 End Or Identify Remote Enable 42 la a a Data Input Output Line 7 i Data Valid GND 6 Ground Wire Twisted pai ian NRFD Not Ready For Data GND 7_ Ground Wire Twisted pai NDAC Not Data Accepted GND 8 Ground Wire Twisted pai i Interface Clear GND 9_ Ground Wire Twisted pai
33. ch temperature readings are taken with current flow in each direction and the corresponding resistivity values are averaged to minimize the noise effect and the thermal voltage building After finishing the measurements all instruments were turned off and the temperature had been raised to room temperature by the temperature controller Finally the vacuum pump was turned off and the sample was removed out of the cryostat 28 5 4 PID Propotional Integral Dervative Temperature Controller Temperature control in industrial applications is an old science taking off mostly during the industrial revolution and coming into its own in the United States early in the Twentieth Century This control was very simple mechanical control that did not go beyond turning a heater or cooling device on or off PID Control however is a fairly new concept that was immediately accepted into use for temperature control applications and gave way to an entire line of PID temperature controllers including the entirely digital 58 units seen at work in most applications today 30 5 4 1 PID Control and its use with temperature PID control stands for and consists of three distinct feedback and control areas A circuit diagram of the control system is shown in the figure 5 5 Figure 5 5 PID Block diagram The circuit is a form of PID controller The input signal is buffered and amplified by a non inverting amplifier and the gain o
34. conductor prepared in our labs with various preparation conditions The phenomenon of superconductivity is having a tremendous impact on the advancement of technology in many fields including medicine and electronics It is expected to have more impact in the future of electric motors power production and transmission transportation and communication systems medical imaging superconducting magnets and accelerators 7 After a sample is synthesized its superconductivity must be measured Because superconductors only exhibit their phenomenal behavior at low temperatures all testing is carried out in cryogenic surroundings under vacuum conditions Traditionally all measurements were painstakingly taken by hand however now measurements of temperature applied current and voltage are controlled received and interpreted by a computer with the help of LabVIEW This leads to design a quite reliable system and methodology to utilize new software and hardware technology in promising field of high temperature superconductivity In this project after this introductory chapter brief literature review instrumentation and experimental results are discussed in the ongoing Chapters Chapter 2 presents a brief review to the history of superconductivity basic properties superconductor and their potential applications Chapter 3 explains the approach for Automation It discusses the requirements of DAQ Boards and External Interface Boards alon
35. d appropriate for some simple menu type VIs where you expect a user to select from one of several buttons that perform different actions The parallel loop design pattern lets you handle multiple simultaneous independent tasks In this design pattern responding to one action does not prevent the VI from responding to another action For example if a user clicks a button that displays a dialog box parallel loops can continue to respond to I O tasks 3 7 Instrument I O This section introduces you to the basic concepts on how to use LabVIEW to acquire data from instruments controlled by GPIB VXI RS 232 and other hardware standards LabVIEW communicates with most instruments through instrument drivers which are 31 libraries of VIs that control programmable instruments LabVIEW instrument drivers simplify instrument control and reduce test development time by eliminating the need to learn the low level programming protocol for each instrument Instruments obey a set of commands to respond to remote control and requests for data When you use LabVIEW instrument drivers you run intuitive high level command VIs such as the Read DC Voltage VI for a digital multimeter or the Configure Time Axis VI for a digital oscilloscope The driver VI you call automatically sends the appropriate instrument specific command strings to the instrument The foundation for LabVIEW drivers is the VISA Virtual Instrument Software Architecture VI
36. d test fixturing Leakage current may be minimized by using good quality insulators by reducing humidity and by using guarding This guard should be run from the nearest device to as close as possible to the sample Using triax cabling and fixturing will ensure that the high impedance terminal of the sample is guarded The guard connection will also reduce measurement time since the cable capacitance will no longer affect the time constant of the measurement Light Currents generated by photoconductive effects can degrade measurements especially on high resistance samples To prevent this the sample should be placed in a dark chamber Temperature Thermoelectric voltages may also affect measurement accuracy Temperature gradients may result if the sample temperature is not uniform Thermoelectric voltages may also be generated from sample heating caused by the source current Heating from the source current will more likely affect low resistance samples since a higher test current 1s needed to make the voltage measurements easier Temperature fluctuations in the laboratory environment may also affect measurements Since semiconductors have a relatively large temperature coefficient temperature variations in the laboratory may need to be compensated for by using correction factors Carrier Injection To prevent minority majority carrier injection from influencing resistivity measurements the voltage difference between the two voltage s
37. dance for different samples by applying a range of frequencies which can be set within the range from 5Hz to 13MHz 44 shown in the Display C 26 The two measured display sections Display A and display B provide direct readout of the selected measurements parameters such as absolute value of provides an average measurements mode which can be selected instead of normal mode Table 4 2 shows parameters measured by Display A and Display B Table 4 2 Parameters measured by Display A and Display B Display A Function Display B Function Z Absolute value of impedance Y Absolute value of Admittance Deg Rad phase angle B Susceptance Q Quality factor C Capacitance D Dissipation factor bnda G Conductance The instrument hp 4192A has HP IB connector in its rear panel the twenty four pin allow us to connect it to the HP IP for remote operations Figure 4 9 shows our set up where we connected the device to the HP IB through GPIB Card the instrument is remotely controlled by a desktop computer using LabVIEW program To control and monitor hp4192A using LabVIEW we designed a special VI to serve our purposes for characterization various materials in the materials lab concentrated by gathering data analyzing data and plotting Cole Cole plots The impedance analyzer VI contains many sub VI s for multi purposes connected with each other and represented by several pages to guarantee a complete control for th
38. e mission that user want to do each page contains many options to accomplish a specific and complete job the home page shown in figure 4 10 offers the main three choices the first 45 is to calibrate the device which we need at each turn on the way of the calibration and the buttons you need are designed at the calibration page shown in figure 4 11 Hp 4192A GPIB CARD LabVIEW Program Figure 4 9 HP 4192A computer interface 46 F Impedence Analyzer File Edit View Project Operate Tools Window Help Figure 4 10 Home page of hp4192A F Cilperation programm vi Front Panel Fie Ecit View Project Operate Tool Window Help eee fo en nae ooo Cib ce ae hi tt pt doraa Fant ri oT Ear 2 A n To calibrate this device 1 Choose a spot frequency then press spot 2 Press open 3 Put the plates in sample holder connect wires then press short Figure 4 11 Calibration page The second choice is Run amp Acquire Data this VI gives you the opportunity to sweep a range of frequencies by choosing a start stop and step frequency also you are able to 47 select the parameters you want to display at display sections A and B such as Z with angle d R G with X B or C with D Run amp Acquire Data Page and part of its block diagram represented at figure 4 12 As you click start button the order is transferred by GPIB Bus to the hp4192A then the device will
39. e are a great number of potential uses for new magnetic field sensing devices The applications for these devices are widespread from simple compass based navigation systems to ultra sophisticated SQUIDs that probe the invisible human biological activities Several magnetic sensors based on various principles have been developed with the specific requirements of each sensor being particular to its application A number of different materials properties may be exploited in sensor application including magnetoresistance giant magnetoimpedance magnetoocaloric magneto optical and magnetostrictation effects Each of these effects will also have its own advantages and 17 disadvantages for a particular field sensing application and device structure and each presently has its own obstacles to be overcome for full integration into new field sensing technologies e Superconducting Quantum Interference Devices SQUID One practical use of superconductors is in detecting very small magnetic fields Not only can superconductors be used to generate magnetic fields greater than 10 T 10 guass they can detect magnetic field below 10 T this remarkable sensitivity is achieved by Superconducting Quantum Interference Devices SQUIDs The underlying principle of a SQUID is tunneling A quantum mechanical effect produces the Josephson Effect In addition SQUID can be used detect corrosion highly sensitive One interesting application of SQUID is detecting
40. e at T 78 83 and 88 K Dependencies of levitation force on levitation gap between two identical permanent magnets Dependencies of levitation force on levitation gap for YBCO sample ZFC without nano pinning sites Dependencies of levitation force on levitation gap for YBCO sample ZFC with nano pinning sites Vil 55 56 59 6l 64 64 65 70 71 71 72 73 76 80 81 82 82 84 85 86 86 88 88 Table 4 1 4 2 LIST OF TABLES DESCRIPTION GPIB signal description Parameters measured by Display A and Display B viii Page 42 45 ABSTRACT STUDYING MAGNETOTRANSPORT PROPERTIES OF SUPERCONDUCTORS USING LABVIEW By Huda Mahmoud Haddad The computer technology and the Internet have the potential to provide a highly interactive and powerful learning environment for physics disciplines We have automated several advanced physics experiments using LabVIEW the industry standard software used for data acquisition and instrument control LabVIEW virtual instruments coupled with data acquisition and control devices were created to interface with a Keithley Current Voltage source and sensitive Nanovoltmeter PID Lake shore temperature controller HP low frequency impedance analyzer Band pass filter stepper motor Shimadzu digital balance and NI ELVIS II bread board The automation of these experiments permits the rapid and easy collection and analysis of data facilitating the student s explo
41. e heater in proportion to the difference in temperature between the oven and the set point Where P is known as the proportional gain of the controller As its gain is increased the system responds faster to changes in set point but becomes progressively under damped and eventually unstable The final oven temperature lies below the set point for this system because some difference is required to keep the heater supplying power 63 The heater power must always lie between zero and the maximum M because it can only source not sink heat Temperate 04 T 500 1000 1500 Time 3 Figure 5 7 Temperature versus time for different gain C Proportional Derivative Control The stability and overshoot problems that arise when a proportional controller is used at high gain can be mitigated by adding a term proportional to the time derivative of the error signal This technique is known as PD control The value of the damping constant D can be adjusted to achieve a critically damped response to changes in the set point temperature as shown in the next figure Temperate C Ticreasine damping E 100 z200 300 400 SOO Time 3 Figure 5 8 Temperature versus time for different damping constant 64 Too little damping results in overshoot and ringing too much causes an unnecessarily slow response d Proportional Integral Derivative Control Although PD control deals neatly with the overshoot and ringing problems a
42. e response curves for example bandpass filter Note symmetry of curves with log frequency and gain scales The precise shape of a band pass filter s amplitude response curve will depend on the particular network but any 2nd order band pass response will have a peak value at the filter s center frequency The center frequency is equal to the geometric mean of the 3 dB 1 2 frequencies f fify where f 1s the center frequency fr is the lower 3 dB frequency 40 and fy is the higher 3dB frequency Another quantity used to describe the performance of a filter is the filter s Q This is a measure of the sharpness of the amplitude response The Q of a band pass filter is the ratio of the center frequency to the difference between the 3dB frequencies also known as the 3dB bandwidth 24 Therefore Q f fy fL 4 3 GPIB 488 2 The IEEE 488 also known as the General Purpose Interface Bus GPIB is a high speed parallel bus structure originally designed by Hewlett Packard 25 It is generally used to connect and control programmable instruments but has gained popularity in other applications such as intercomputer communication and peripheral control Figure 4 7 a GPIB CARD Figure 4 7 b GPIB USB HS The GPIB is a link or bus or interface system through which interconnected electronic devices communicate Hewlett Packard invented the GPIB which they call the HP IB to connect and control programma
43. ectronic phenomenon it nevertheless depends in an important way on the vibrations of the crystal lattice in which the electrons move The discovery of Josephson Effect in 1962 opened up exciting potential for the use of Superconductors in measurement science and in high speed electronic devices 12 According to Josephson quantum tunnelling effects should occur when a supercurrent tunnels through an extremely thin layer 10 A of an insulator Josephson tunnelling of paired electrons through an insulating barrier 1s remarkable in that the tunnelling amplitude is that of an individual pair despite the fact that the pairs comprise a correlated many body condensate BCS Bardeen Cooper Schriefer theory of superconductivity explains most of the phenomena associated with it and provides the basis for our present understanding of superconductivity in conventional low temperature superconductors and to some extent plays a role of reference theory in the on going search or a correct description of superconductivity in the recently discovered high temperature superconductors HTSCs cuprates doped fullerenes MgB2 13 Until 1986 the highest Tc observed for any superconductor was only 23 2 K in an alloy of niobium aluminium and germanium This meant that superconductors had to be cooled by liquid heltum an expensive and sometimes unreliable process All this suddenly changed with the discovery of Bednorz and Muller of high tempe
44. ed bench top workstation a prototyping board a multifunction data acquisition device and LabVIEW based virtual instruments 5 This combination provides an integrated modular instrumentation platform that has comparable functionality to the DMM Oscilloscope Function Generator and power Supply found on the laboratory workbench The NI ELVIS II Workstation can be controlled either vi manual dials on the stations front or through software virtual instruments The NI ELVIS II software suite contains virtual instruments that enable the NI ELVIS II work station to perform functions similar to a number of much more expensive instruments One can use NI ELVIS II in engineering physical sciences and biological sciences laboratories The suite offers full testing measurement and data logging capabilities The environment consists of the following two components 5 1 Bench top hardware workspace for building circuits shown in Figure 4 1 2 NI Elvis software interface consisting of twelve soft front panels SFP instrument figure 4 2 The soft panels are 33 e Digital Multimeter DMM e Oscilloscope Scope e Function Generator FGEN e Variable Power Supply VPS e Bode Analyzer e Dynamic Signal Analyzer DSA e Arbitrary Waveform Generator ARB e Digital Reader DigIn e Digital Writer DigOut e Impedance Analyzer e Two wire Current Voltage Analyzer e Three wire Current Voltage Analyzer Figure 4
45. ed surface structure so the measured resistance is interpreted to be only the bulk value but under special conditions where the bands bend sharply under the surface to produce a carrier accumulation layer or in high vacuum where the sample crystal has a well defined surface superstructure to produce a conductive surface state band the contributions from the surface layers cannot be ignored Even under such situations however the surface contributions have been considered to be very small because as shown in figure 5 3 the measurement current flows mainly through the underlying bulk in the case of macroscopic probe spacing Silver paste Superconductor sample Voltage leads Current leads Copper sample holder Figure 5 4 Real photo for the 4 probe connections 56 5 3Measurements procedure The following steps were followed in our measurements l The surface of the sample was polished by an emery paper and was cleaned by acetone The sample was placed on the cooper sample holder which is mounted on the cold head of the cryostat using double faced sticker to stick the sample to the sample copper holder Four probes two for current and two for voltage were connected to the sample surface by silver paint During the application of silver paint one should take care about the amount of silver paint that is used for the contacts by minimizing the spot diameter of the silver paint because it affects the value of the re
46. elp LabVIEW A wide variety of new superconductive compounds are now being made using different methods and various substrates under an assortment of different conditions In the near future the automated system we have developed will be used to characterize great number of samples quickly by characterizing up to four potential new superconductors simultaneously Because this system is automated by LabVIEW once the user defines the parameters of the sample set the program will run unmonitored for its duration temperature changing rates The storing of data is also a useful feature of the system allowing the user to manipulate the measurements in a variety of ways even after the run has taken place 93 10 Il 12 I gt 14 15 References Travis J Internet Applications in LabVIEW USA Prentice Hall 2000 601 0 13 014144 5 Myler H R Early Engineering Concepts Engagement in a Freshman Level Introductory Course Proceedings of the 2004 ASEE Gulf Southwest Annual Conference 2004 Texas Tech University LabVIEW Fundmental National instrument corporation Aug 2007 165 374029C 01 Sapijaszko C Sapijaszko G An Innovative Electronics Laboratory System for On Campus and Distance Learning Applications Proceedings of the 2004 American Society for Eng Education Annual Conference amp Exposition 2004 USA NI Eductional Laboratory Virtual Instrumentation Suite I NI ELVIS ID User Manual National Instrument Corpor
47. ensing terminals should be kept at less than 100mV ideally 25mV since the thermal voltage kt q 1s approximately 26mV The test current should be kept to as low as possible without affecting the measurement precision 67 5 7 I V and R T programs Studying magneto transport prosperities of superconductors such as critical temperature Tc critical current Ic and the effect of nano particle addition on the current voltage curves at different temperatures are our main interst For this purpose we built our set up including Lakeshore Temperature Controller model 3318S to control and monitor the set point temperature through PID tuning system this will be achieved by setting the set point with a suitable PID values The case is not always done in an easy way especially when you want to reach a stable cryogenic temperature close to liquid nitrogen LN2 atmosphere where we can t control its evaporation So in such conditions we should wait for about fifteen minutes to monitor the temperature and ensure that it still stable The second instrument in our set up is the Current voltage source measure Kethiley model 2425 The time at which the temperature controller reaches the set point at the stable state is the suitable time to take our measurements by applying the current values and recording voltage measurements And repeating this several times Special care should be taken for the temperature fluctuations due to sample heating
48. erface The front panel is the user interface of the VI You build the front panel with controls and indicators which are the interactive input and output terminals of the VI respectively Controls are knobs pushbuttons dials and other input devices Indicators are graphs LEDs and other displays Controls simulate instrument input devices and supply data to the block diagram of the VI Indicators simulate instrument output devices and display data the block diagram acquires or generates e Block diagram Contains the graphical source code that defines the functionality of the VI After you build the front panel you add code using graphical representations of functions to control the front panel objects The block diagram contains this graphical source code Front panel objects appear as terminals on the block diagram Additionally the block diagram contains functions and structures from built in LabVIEW VI libraries Wires connect each of the nodes on the block diagram including control and indicator terminals functions and structures e Icon and connector pane Identifies the VI You can use the VI in another VI A VI within another VI is called a subVI A subVI corresponds to a subroutine in text based programming languages LabView program also contains the following three types of pallet which give you the options you need to create and edit the front panel and block diagram e Tools Palette The Tools palette is available on the front pa
49. ethod to measure electrical conductance The distribution of current flowing through a superconductor specimen is also schematically drawn The two outer probes are used for sourcing current and the two inner probes are used for measuring the resulting voltage drop across the surface of the sample The inner pair of probes picks up a voltage drop V along the surface due to the resistance of the sample Thus one can obtain a four probe resistance R V I strictly speaking it is multiplied by a correction factor depending on the specimen shape and probe arrangement Owing to this configuration one can correctly measure the resistance of the sample without any influence of contact resistance at the probe contacts irrespective of whether the probe contacts are Ohmic or of Schottky type This is because no current flows through the inner pair of contacts so that no voltage drops at the probe contacts occur 29 This is a great advantage in the four point probe method The volume resistivity is calculated for disk shape sample as follows 55 p m In2 x V D x tx k 5 1 where p volume resistivity Q cm V the measured voltage volts I the source current amperes t the sample thickness cm k a correction factor based on the ratio of the probe to wafer diameter and on the ratio of wafer thickness to probe separation In the case of measurements in air the sample surface is usually dirty and does not have a well order
50. ey can create an air gap magnetic field without any losses The performance advantages of a high temperature superconductor motor over that of a conventional motor include the following high power density than a conventional motor due to the large air gap magnetic field produced by the lossless high temperature superconductor winding and higher efficiency 14 than a conventional motor due to the lossless superconductor winding and smaller motor size The high temperature superconducting motors are much smaller lighter and more efficient when compared to a conventional motor as it appears in the Figure below Utilities and industry will be able to lower their electricity costs by using these motors Figure 2 8 High temperature superconducting electric motors e High Temperature Superconductor Transformers It offers utilities and industry a highly efficient lightweight compact and environmentally friendly alternative to today s oil filled transformers e Fault Current Limiters It can protect power transmission cable and operating equipment from surges of excess electricity caused by lightening strikes short circuits and power fluctuations The high temperature superconductor coils in the fault current limiter control the high current burst just long enough for the circuit breaker to open The advantage of using a superconductor in a fault current limiter is that the resistance zero when in the superconducting state which is nearly
51. f this stage defines the proportional gain P of the controller The amplified error signal passes in parallel through an integrator top a unity gain amplifier middle and a differentiator bottom all of which have inverting behaviour Their outputs are then summed and inverted by the final op amp and passed to the output The potentiometers labelled D and I control the proportions in which derivative and integral fractions contribute to the output signal which is proportional to the power W to be supplied to the heater A Proportional The first of these areas 1s proportional The output of the proportional controller is relative to the difference between the temperature that is present and the set point An adjustable proportional band is set up as either a range of temperatures or a percentage of the set 59 point temperature and is located below the set point The Proportional band is good for reducing the rise time of a process and reduces but never erases the steady state error B Integral The second system in a PID controller is the integral control The integral control eliminates the steady error but makes the transient response worse The integral eliminates the droop caused by the proportional band Since the power level at set point is zero and near zero right before it the temperature settles at a point slightly below the set point using just proportional control this results in a droop down from the se
52. from 200 to 350 miles apart relieving congested highways and airports The superconducting magnetic coils on board the train and on the sidewalls of the guide way provide levitation keep the vehicle in the center of the guide way and propel the vehicles along the track e Superconducting Magnets Superconducting magnets can be used in Nuclear Magnetic Resonance Imaging NMRI MRI in hospital and in high energy physics accelerators MRI is a noninvasive technique for seeing inside the body which uses no ionizing radiation The Superconductive magnetic coils are an important portion of this whole body scanner Since these coils are capable of producing very stable large magnetic field strength of magnets Conventional magnets cannot produce very high magnetic field superconductors 16 can generate more than 10 T magnetic field An important factor limiting the magnetic field of an accelerator is the difficulty of making tapes and wire Figure 2 9 The Yamanashi MLX01 MagLev train e Power Electronics The purpose of power electronics is usually to switch large currents without having any moving mechanical parts a transistor that changes states from on to off is the heart of the device Because high temperature superconductors can switch from superconductive state to nonsuperconductive state in very short time high temperature superconductor are very good candidates for this application e Magnetic field Sensors Ther
53. g with the tools that have to be used in automation LabVIEW and NI EVIS II Chapter 4 explains the implementation of this approach to specific experimental set ups such as impedance analyzer and bass filter using NI ELVIS II Chapter 5 describes experimental set up such as PID temperature controller Voltage Current Characteristics and resistivity measurements using d c four probe method and levitation force set up and other related techniques The LabVIEW code used for automation is also explained for each set up Chapter 6 discusses the results obtained from various experiments and the merits of such an automation approach and its applications In Chapter 7 we will draw our conclusions and future work Chapter Two Superconductivity 2 1 Brief History of Superconductivity A large number of metals and alloys when sufficiently cooled down to temperatures nearing 0 K the dc electrical resistivity abruptly drops from a finite value to one that 1s virtually zero and remains there upon further cooling Materials that display this behaviour are called superconductors and the temperature at which they attain superconductivity 1s called the critical temperature Tc Super conductivity 1s a very old and exciting field discovered by H Kammerlingh Onnes in 1911 8 He showed that dc resistivity in mercury disappeared altogether at the critical temperature Tc 4 2 K Since its discovery in 1911 a great number of metals and alloys were found to exhibit
54. gerant Prototype levitated trains have been constructed in Japan by using superconducting magnets Superconducting magnets are already crucial components of several technologies Magnetic resonance imaging MRI is playing an ever increasing role in diagnostic medicine The intense magnetic fields that are needed for these instruments are a perfect application of superconductors Similarly particle accelerators used in high energy physics studies are very dependant on high field superconducting magnets The recent controversy surrounding the continued funding for the Superconducting Super Collider SSC illustrates the political ramifications of the applications of new technologies 18 New applications of superconductors will increase with critical temperature Liquid nitrogen based superconductors has provided industry more flexibility to utilize superconductivity as compared to liquid helium superconductors The possible discovery of room temperature superconductors has the potential to bring superconducting devices into our every day lives High temperature superconductors are recent innovations from scientific research laboratories New commercial innovations begin with the existing technological knowledge generated by the research scientist The work of commercialization centers on the development of new products and the engineering needed to implement the new technology Superconductivity has had a long history as a specialized field of physics
55. gle filter The result is called a band pass filter Creating a bandpass filter from a low pass and high pass filter can be illustrated using block diagrams Figure 4 5 High Pass Gain Low Pass Function out from NI EL VIS SAA 10kohm 10kohm Analog Channel 0 Alternative Analog Channel 0 when demostrating NI EL VIS Figure 4 5 Block diagram for band bass filter 38 The Band Pass filter demonstrates how Op Amps can be used to filter signals The experiment allows for monitoring the filer in three locations after the high pass stage after the gain stage and after the low pass stage for the final result 24 The experiment uses the NI ELVIS Oscilloscope Function Generator and Bode Analyzer instruments The high pass filter has a frequency response of l l fo QnVR2R3CiC3 2y 1 2k 1 2k lu ly 132 6Hz The gain stage has a gain of Vout l F R Vin T ky 1 1Vin Rs Figure 4 6 a shows the input and output frequencies Also the curves of gain vs frequency and phase vs frequency are plotted and commonly used to illustrate filter characteristics The magnitude of the transfer function has a maximum value at a specific frequency 9 between 0 and infinity and falls off on either side of that frequency A filter with this general shape is known as a bandpass filter because it passes signals falling within a relatively narrow band of frequencies and attenuates signals outside of that band The range of fre
56. he behavioure of the sample in case of a bad contact and good contacts resistance of several Ohms is considered to be good contact Measurement variability includes the general procedure as well as repeatability and accuracy of voltage current temperature and contact separation measurements Damage variability includes thermal cycling time handling and lab environment These are only partial lists of possible sources of variability Although all of these effects are considered here results were not always definitive because of the many concurrent effects and the limitation of time 83 To determine the critical current Ic of the superconducting sample at a given temperature the voltage is measured as a function of the sample current using the four point probe method A 10 uV criterion value is used This criterion represents the voltage value below which the sample is considered to be superconducting In practice the voltage versus current curve rise rapidly at Ic and the exact value of this criterion is not critical At first sight it is conceptually an easy measurement to determine the critical current Ic in a sample then just a matter of geometry to divide out the cross sectional area to get the critical current density Jc But reality is not that much simple Great care must be taken while determining Ic from the I V curves because at I Ic the voltage suddenly rises and the sample becomes normal Accordingly it is not easy to de
57. he controller This means that the computer acts as the controller and is able to tell an instrument to be either a talker it tells the controller what value it s at or a listener the controller tells it what value to go to The card coordinates these transfers of information 21 LabVIEW is the connection between the GPIB card and the data from the experiment LabVIEW program works through a GPIB card to control the instruments take measurements and organize the results Automated data acquisition greatly decreases the amount of human error can be left to run on its own and can be run regardless of the skill or experience of the user LabVIEW programming uses icons instead of lines of text to create applications In contrast to text based programming languages where instructions determine program execution LabVIEW uses dataflow programming where the flow of data determines execution 20 In LabVIEW you build a user interface by using a set of tools and objects The user interface is known as the front panel You then add code using graphical representations of functions to control the front panel objects The block diagram contains this code In some ways the block diagram resembles a flowchart You can purchase several add on software toolsets for developing specialized application All these toolsets integrate seamlessly in LabVIEW LabVIEW is integrated fully for communication with hardware such as GPIB VXI PXI RS 232
58. he flux lines will penetrate the superconductor If the magnet is moved away from the superconductor the magnetic repulsive force will decrease the variation of the repulsive force with the high of the magnet when it is approaching and when it is moving away will discussed in chapter six 74 The shape of the function that relates the levitation force to the highet of the magnet is somewhat like a banana so its called force banana Rossing and Hull described the forces on a moving magnet they explain it by the presence of an eddy current that can make the superconductor acts as a magnetic mirror where the magnet being repelled by its magnet mirror that induced below the superconductor the faster the rotation of the magnet the better the magnet it produce The levitation force is magnetic in nature and in order to evaluate it we have to follow the magnetic principles and instructions Starting with the relation that relates the magnetic potential to the magnetic force F VU where the magnetic potential can be calculated from the magnetic induction or U m B where mis the magnetic moment of the magnet 32 The magnetic induction can be evaluated by using the vector potential where B VxA In this section we shall discuss some of these methodologies of the magnetism that can be followed in order of evaluating the magnetic levitation force The levitation force depends on many factors such as the geometry of the superconduc
59. hich are used in common labs ELVIS hardware and software integrated to gather to serve multi function as described below DMM The primary DMM instrument on NI ELVIS II is isolated and its terminals are the three banana jacks on the side of the bench top workstation For DC Voltage AC and COM 36 Voltage Resistance Diode and Continuity Test modes use the V connectors For DC Current and AC Current modes use the A and COM connectors 5 For easy access to circuits on the prototyping board you can use banana to banana cables to wrap the signals from the user configurable banana jacks to the DMM connectors on the bench top workstation Oscilloscope The two oscilloscope channels are available at BNC connectors on the side of the input impedance and can bench top workstation These channels have robust M be used with 1X 10X attenuated probes You can also use high impedance Analog Input channels lt AI 0 7 gt available on the prototyping board Function Generator FGEN The function generator output can be routed to either the FGEN TRIG BNC connector or the FGEN terminal on the prototyping board A 5 V digital signal is available at the SYNC terminal The AM and FM terminals provide analog inputs for the amplitude and frequency modulation of the function generator output 5 Power Supplies The DC power supplies provide fixed output of 15 V 15 V and 5 V The variable power supplies provide adjustable output voltages from 0 to
60. igure 5 13 The resistance is calculated using Ohms law where we apply a constant current into the sample in the two directions positive and negative to minimize the thermal voltage that may be affect on the real reading The current is divided by the average of the voltage reading to get the resistance all the options are also available as shown in the previous program to control lakeshore And the data is automatically saved into excel sheet 72 eee tl nn ee Appkcation Fort tor ma ee a L3315 Off SET Teme Point Heater range Apply current seconds to wait 200 amor I value K2425 otf TEMP K R Ohm Voltage V Figure 5 13 Front Panel of R T VI program i ee LI cd TODO DEG PO De DD Oe OO eT SED ED agapan QuQ ahahaha hahahahahahaha hahah of ahahaha ahahaha hahahahaha hale s J l P 1 2 octal integer 4 a Jeg Apply current ES bd th fa bet fe Cd ah tal od et TY AE AAA is FORMELE VOLT _ E SER ee TT 7 ee ee PHEeLoOODOOoeeeoeoeooooooe ooo HHOOOOOHoOooooODODo ooo MHonoooDoOoOoHHoooooODOD OE THODUDODOHODOODOOHUoOOUP op oOoOoDooe aial A NENET ji maha fee el gua an ais lanl oma sa iai P eb n b a aa in le bea a m i m aa a a wn ne ll ee nl el aa aa m ma m De ee a ETETETT TATANEN ER EEEE TETEE a ee z EPET VERTETEN el ENEE ee A E A eal fee ed E fff el GE E lel et A GE i Ge ed ol Se ed ol ed kl ed do ee Dal C T 73 Figure5 14 Part of the B
61. ime to program the devices for such systems and the user has little control of the internal system In today s rapidly changing environment manufacturers want to be able to improve the processes continually This can require being able to alter the monitoring and control of the individual process To accomplish these changes a generic approach for monitoring and control of processes and equipment is desired The main emphasis of this work is to develop a methodology for automatic monitoring and control of all electronic devices in our superconductivity and magnetic measurements laboratory and other related labs at the physics department using readily available hardware and software while still providing tight control over the measurements sensitivity of all parameters for optimum productivity and time saving The challenge is to achieve improved performance by monitoring and controlling parameters using readily available and modifiable systems This can be done by using a data acquisition DAQ and control system with LabVIEW a graphical programming language tool Data acquisition is the process of bringing a real world signal such as voltage into the computer for processing analysis storage or other manipulation Each process is characterized by certain parameters like vacuum pressure light intensity temperature noise and RF power Using a PC based DAQ and control system run by LabVIEW it is possible to control the equipm ent with a hardwa
62. ing language used was LabVIEW The automated experiments consist of 1 A low temperature R T and I V characteristics set up for superconducting materials semiconductors magnetic materials ceramics etc 2 An automated magnetic levitation force measurements set up designed for magnet magnet and superconductor magnet levitation systems 3 A low frequency impedance analyzer 4 A standard NI ELVIS II set up used for testing the programs for simple electronic circuits and devices and interfacing examples before dealing with quite difficult automation systems such as PID control and senescing devices for low resistance and low temperature measurements A huge effort has been done to control all these devices by taking into account all critical parameters involve in such advanced experiments To do this one should understand the deep physics behind each individual sample explain its strange behavior optimized the best measurements conditions check the data reproducibility and add the final touches for the ideal program which well describe the sample story In the semiconductor lab a tremendous amount of work has been established to control all the parameters and we were able to manage and control thousands of data in just few minuets The only problem we faced in this lab was due to lack of high memory in our established computer and this problem can be solved by using a better computer with high ram up to 8 Giga byte memory since the low i
63. l possible practical applications of high temperature superconductors depend on their ability to carry large currents we have determined the critical current density Jc The critical current density is the critical current Ic per area at which the material still remains superconductivity Critical currents are desired as a function of both temperature and applied magnetic field since a variety of theories discuss these functional relationships and applications may required either or both of these data In this work we could not conduct our I V measurements at applied magnetic fields because of the quite old magnet power supply available at our lab However we present our prototype data at zero applied magnetic field The critical current of a to measure accurately and these measurements are often subject to scrutiny and debate This is especially true for measurements on HTSC samples where many factors can cause variability For the purpose of this discussion we have separated the sources of variability in critical current measurements into four groups sample mounting measurement and damage Sample variability includes sample in homogeneity Ic repeatability and hysteresis of the temperature and the thermal voltage Mounting variability includes solder temperature bonding agent and substrate material and contact quality for example Figure 6 5 represents the I V curves of the YBCO sample with different contact soldering methods The curves show t
64. le space must be evacuated to investigate a perfect temperature controlling so the cryostat contain the vacuum space valve connected with vacuum rotary pump As you see in Figure 5 2 the cryostat was placed between the poles of the magnet and the sample stick was able to turn in different directions so we can take the measurements with different magnetic field directions perpendicular or parallel to the sample surface The temperature dependence of the resistivity and superconducting transition temperature were measured by the standard four probe techniques the main parts of the set up are described as follows 28 ogrammable 100 W SourceMeter from KEITHLEY model 2425 with source voltage from 5uV to 105V and measure current from 100PA to 3 165A l A cryostat the cryostat dewar is used for low temperature measurements This dewar has three independent spaces The first 1s the vacuum space that 1s evacuated 52 to provide thermal isolation The second space consists of a reservoir that contains liquid nitrogen The third and innermost region is the central sample tube which contains the sample holder and the electrical connections Figure 5 2 2 Digital temperature controller from LakeShore model 331 with a silicon diode sensor measures better than 0 1 K 3 Electromagnet model Oxford 4 Vacuum rotary pump together with vacuum valves and gauge vacuum 10 mbar 5 Current Voltage source up to 20A 6 Accessories
65. ll then parameter values can be found to give an acceptably damped response with the error temperature eventually tending to zero if the set point is changed by a step or linear ramp in time Whereas derivative control improved the system damping integral control eliminates steady state error at the expense of stability margin 5 6 Sources of Error and Measurement Considerations For successful resistivity measurements the potential sources of errors need to be considered Electrostatic Interference Electrostatic interference occurs when an electrically charged object is brought near an uncharged object Usually the effects of the interference are not noticeable because the charge dissipates rapidly at low resistance levels However high resistance materials do not allow the charge to decay quickly and unstable measurements may result The erroneous readings may be due to either DC or AC electrostatic fields To minimize the effects of these fields an electrostatic shield can be built to enclose the sensitive circuitry The shield is made from a conductive material and is always connected to the low impedance FORCE LO terminal of the SMU The cabling in the circuit must also be shielded Low noise shielded triax cables are supplied with the Model 4200 SCS 66 Leakage Current For high resistance samples leakage current may degrade measurements The leakage current is due to the insulation resistance of the cables probes an
66. lock diagram of The R T VI 5 8 Levitation Force Since the superconductor in the Miessner state will expel any magnetic field inside it any small magnet will be floated in the air if it 1s putted above the superconductor The magnetic force that arises between the superconductor and the floating small magnet 1s called the levitation force which is magnetic in nature and large enough to overcome the gravity due to the weight of the small magnet In 1990 an experiment was done by Shoji Tanaka to levitate a large thick cylinder above an equally large piece of YBCO superconductor Another phenomenon in the levitation over high temperature superconductor HTSC is the spontaneous rotation of the magnet A magnet at rest will oscillate firstly with the rotational amplitude increasing with time until it reaches its maximum value in one direction and a complete rotation occurs making the magnet to keep rotating in that direction with a maximum rotational frequency of 1 Hz The levitation force arises between the superconductor and the magnet is stronger when the two objects are closer and the behavior of the levitation force differs according to the type of the superconductor In type II superconductors the behavior is also differs depending on the magnet if it s approaching or moving away from the sample If the magnet approaches the superconductor it will make the superconductor to reach the minimum critical magnetic value A and more of t
67. lp window to see what khe connections to this Function should be Figure 3 6 LabVIEW Error list window 3 4 Virtual Instrumentation Virtual instrumentation combines hardware and software with industry standard computer technologies to create user defined instrumentation solutions National Instruments specializes in developing plug in and distributed hardware and driver software for data acquisition DAQ IEEE 488 GPIB PXI serial and industrial communications The driver software is the application programming interface to the hardware and is consistent across National Instruments application software such as LabVIEW LabWindows CVI and Measurement Studio These platforms deliver the sophisticated display and analysis capabilities that virtual instrumentation requires You can use virtual instrumentation to create a complete and customized system for test measurement and industrial automation by combining different hardware and software components Many instruments are external to the computer and do not rely on a computer to take a measurement By connecting instruments to a computer you can programmatically control and monitor the instruments and collect data that you can process 27 further or store in files You can install some instruments in a computer similar to general purpose DAQ devices These internal instruments are called modular instruments Regardless of how you connect to an instrument the computer must use
68. measurements in an vi Page 33 5 4 5 5 5 6 5 7 5 8 5 9 5 10 5 11 5 12 5 13 5 14 5 15 6 1 6 2 6 3 6 4 6 5 6 6 6 7 6 8 6 9 6 10 external magnetic field a Macro and b micro four point probe method to measure electrical conductance The distribution of current flowing through a superconductor specimen 1s also schematically drawn Real photo for the 4 probe connections PID Block diagram Temperature vs Time Auto tuning Temperature versus time for different gain Temperature versus time for different damping constant Relation between temperature and generated power as a function of time Experiment set up Front panel for kethiley amp lakeshore VI Part of kethiley amp lakeshore block diagram Front Panel of R T VI program Part of the Block diagram of The R T VI Levitation experiment set up Sample preparation procedures Resistance versus temperature for pure and nano added YBCO sample in the temperature range 70 to 150 K The critical temperatures criteria are shown Resistance versus Temperature curve for YBCO sample with nano inclusion Resistance versus Temperature curve for pure YBCO sample Example of I V curves for the pure YBCO sample with different contacts using silver epoxy The good and bad contacts are indicated I V characteristics of YBCO at different temperatures shown various voltage criteria used to determine critical current Ic1 Ic2 and Ic3 I V characteristics of YBCO sampl
69. mpedance analyzer require many local 91 variables and according to national instruments who invented the labVIEW using local variables will make the program run slower on low computer memory Anyhow this problem might be solved by saving the data to other compatible program such as Origin which has a good build in interfaces with LabVIEW then delete the old data that were collected on the back ground of the LabVIEW Since our mission in this thesis for this lab was to control the low impedance analyzer through an IEEE card by the computer we delayed solving this problem to near future Using LabVIEW is in great importance of doing experiments especially if something goes wrong during the real time of doing the experiment rather than taking the data manually then again re interred them manually on any spread sheet and figure out the problem after drawing the required graph one can figure out from the beginning if something goes wrong or not while the experiment is still running due to the ability of analyzing real time data In all the above experiments we were able to control and run the experiments over our intranet group works at distance and analyze the data at distance while the setup is still running It is worth mentioning that all the programs can run on any windows machine with out the need of LabVIEW license by running an executable small exe file During the intensive work in the superconductor lab we face s
70. n presence of magnetic field The results will be discussed in the next chapter 79 Chapter Six Results and Discussions 6 1 Sample preparation The pure Al O3 nanoparticles added YBCO samples used in this study were prepared by the conventional solid state reaction method 28 Stoichiometrically high purity 99 9 powders of BaCO3 Y2O3 and CuO according to the chemical formula of Y Ba Cu 1 2 3 were thoroughly mixed and ground in a mortar for 2 h to get a powder of uniform gray color The powder was then placed in crucible centered in three zone furnace and heated for 1 h at 500 C at the rate of 20 C min to ventilate the CO2 gas The temperature was raised to 850 C at the same rate and the powder was heated at this temperature for 10 h to get a powder with dark gray to black color the powder was then cooled down to room temperature and reground for 1 h The powder was divided to several samples and Al203 nanoparticles with size of 10 nm were added to the samples as a weight ratio After the addition of Al O3 each sample was ground separately for another 1 h the pellets were pressed under a pressure of 10 tons placed in ceramic boat and centered in the three zone furnace The furnace was heated to 950 C held at this temperature for 10 h At this stage the structure Y Ba2Cu307 5 1 x Al203 x 1s formed by inter diffusion of ions but it has a deficiency of oxygen content The samples were then cooled to 550 C at which i
71. nce SHIMADZU with 1 mg resolution and 220 g capacity On the measuring pan of the balance we attach upside down a 15 cm height teflon cup where an iron plater is glued with epoxy A permanent magnet is magnetically fixed to the plate The magnet has to be far from the sensitive digital balance electronics Components of the balance are supposed to be nonmagnetic We use Nd Fe B magnets with different shapes and strengths cylindrical ringular cubic etc with a field ranges from u oH 0 1 T to 0 2 Tat the plane surface that decays down to less than 0 001 T on the balance pan Care must be taken to center the pair magnet 77 superconductor with respect to a vertical axis pointing to the middle of the rectangular pan The superconductor pellet is properly fixed inward a second small teflon cup at the bottom s center The upper cup was filled with liquid nitrogen to keep the sample at liquid nitrogen temperature T 77 K lt Tc for more than 15 minutes which quite enough time to do the measurements The cup is rigidly attached to a commercial satellite dish stepper motor with an arm controlled by the computer using a control unit NI ELVIS The arm can be moved vertically by means of the gear system to change the distance between the sample and the magnet A ruler graduated in millimeters is used for measuring the distance between them A calibration curve was done for the distance versus the motor voltage to get an accuracy of better than
72. nel and the block diagram A tool is a special operating mode of the mouse cursor When you select a tool the cursor icon changes to the tool icon Use the tools to operate and modify front panel and block diagram objects e Controls Palette 22 The Controls palette is available only on the front panel The Controls palette contains the controls and indicators you use to create the front panel e Functions Palette The Functions palette is available only on the block diagram The Functions palette contains the VIs and functions you use to build the block diagram 3 The figure below shows the three types of pallets E gt Functions alee Tools X tee mae NIG ae ain Ce Figure 3 1 Tools Controls and function pallets 3 3 Programming by LabVIEW In this section we will illustrate briefly how to program a simple VI and how to deal with LabVIEW environment and its features LabVIEW program differs from text based programming languages which need specific commands to program One who uses LabVIEW needs to know the available functions and controls in addition to learn their properties and options also he should know the rules that must to be obeyed through the programming LabVIEW first window called Getting Started window figure 3 2 from here you can create a new application open an existing application show some help resources and view examples by LabVIEW 23 Getting Starte Ele persto Joo Hele
73. nsition temperature can be determine by 80 dividing the transition region into three transitions Tc onset Tc mid and Tc offset as seen in the following figure YBCO nano Al_0 O YBCO R mOhm 70 80 90 100 110 120 130 140 150 T K Figure 6 2 Resistance versus temperature for pure and nano added YBCO sample in the temperature range 70 to 150 K The critical temperatures criteria are shown Figures 6 3 6 4 shows a typical R T curve for a rectangular shaped pure and nano Al203 added YBCO sample in the temperature range from 78 K to 300 K For example figure 6 2 shows a close look to the R T curves for both samples in the temperature range 70 K to 150 K Tc onset 92K Tc mid 88 K Tc offset 85 K and the transition width ATc 7 K for the YBCO sample with nanoparticles inclusions However pure YBCO sample exhibit a sharper transition temperature with Tc onset 89 K and a smooth R T curve 8 1 compared to the sample with nanoparticles inculsions This behavior may be attributed to the formation of nonsuperconducting impurity phases and Al O3 nano phases or clusters which alter the normal state resistance above Tc DO 100 150 200 250 300 TKJ Figure 6 3 Resistance versus Temperature curve for YBCO sample with nano inclusion g 7 6 5 Z ao 4 az 50 100 150 200 250 300 TUR Figure 6 4 Resistance versus Temperature curve for pure YBCO sample 6 3 I V Characteristics Since severa
74. o fit the experimental results The Bean model has also been applied to explain the levitation force of the experimental measurements 36 The levitation force between a superconductor and a magnet can be calculated by the following formula F m dB dz where m is the magnetic moment of a superconductor dB dz is the magnetic field gradient produced by the external field M is the magnetization per unit volume A is a constant depending on the sample geometry J 1s the critical current density of a superconductor and r is the radius of a shielding current loop This indicates that it is necessary to have r Je and dB dx as large as possible to acquire a high levitation force Many workers have studied and reported on the theoretical details between a superconductor and a permanent magnet 37 40 The levitation forces between samples and the magnet were measured under zero field cooled ZFC at T 77 K The maximum levitation force measured in this experiment was taken at the smallest gap 2 mm between the two nearest surfaces of the sample and the magnet Figure 6 9 shows the dependencies of levitation force on levitation gap distance between the YBCO sample and the magnet in zero field cooled ZFC state at 77 K The hysteresis behaviors were also obtained for the cases when we used magnets with cubic and rectangular shapes 87 es Incressing distance Cecreasing d stance F 10 N mm Figure 6 9 Dependencies of levitation fo
75. o many hard moments in each step of sample preparation making primary set up interfacing obtaining a good vacuum cooling down to liquid nitrogen temperature and playing with antivirus software and program bugs However we have also faced fantastic moments when we get good results and we reach the point that we feel that we have a strange human device relations with all our instruments A special relation is developed between us and our 92 superconducting samples in such away that we behave like a superconducting humans at room temperature The ability to operate at high temperatures makes superconductors accessible and economically feasible for use in industry They can be used in the development of transmission lines levitation electric motors medical and aerospace applications The rapid characterization and testing of potential superconductors is therefore important to both science and industry Here is a summary of what we have done during the last several months After a sample is synthesized its superconductivity must be measured Because superconductors only exhibit their phenomenal behavior at low temperatures all testing is carried out in cryogenic surroundings under vacuum conditions Traditionally since the last three years all measurements in our lab were painstakingly taken by hand however now measurements of temperature applied current and voltage are controlled received and interpreted by a computer with the h
76. of our source Samples with relatively low J are suitable for our I V set up vim o 0 2 0 4 0 6 0 8 1 1 2 I A Figure 6 6 I V characteristics of YBCO at different temperatures shown various voltage criteria used to determine critical current Ic1 Ic2 and Ic3 85 yim Figure 6 7 I V characteristics of YBCO sample at T 78 83 and 88 K 6 4 Magnet Magnet Levitation force As a test measurement of the levitation force for our automated set up we have conducted a simple experiment to measure the repulsive force between two identical permanent magnets The magnets were fixed on the plastic cups exactly in a coaxial position to minimize the variation of the magnetic force with the lateral and vertical direction Figure 6 8 shows a typical hysteresis force curve for the two magnets 400 350 300 250 200 F A N 150 100 50 Zamm Figure 6 8 Dependencies of levitation force on levitation gap between two identical permanent magnets 86 6 5 Superconductor Magnet Levitation Force The magnetic force between HTSCs and permanent magnets PMs has been studied by several researchers to further the basic understanding of superconductivity 33 35 The force calculations were based upon the critical state model of Bean The results of this investigationcon firms the suggestions that the lateral force is due to flux trapping Johansen et al 35 extended these results by using a more realistic field profile t
77. oolean logic signal analysis and more The first step on programming after planning is to put your controls and indicators which you need in the front panel again controls are input elements where you can adjust the values or text Indicators are output elements which is used to indicate values text or 24 graphs Figure 3 3 shows the front panel for a simple VI which add two numbers and subtract them Here we placed two numeric controls and two numeric indicators CONTROLS INDICATORS Figure 3 3 The front panel for addition amp subtraction VI In the block diagram An icon appears for each control and indicator there we need to add and subtract the two numbers stored in the controls and display the answer in the indicators So the two functions Add and subtract are used to do this process and wires used to connect between controls functions and indicators guarantee the data flowing through the VI Figure 3 4 shows the block diagram for this example This diagram executes the two numbers adding and subtracting gt 1122 Subtracvzt Figure 3 4 The block diagram for addition amp subtraction VI The control icons or functions in the block diagram have tow kind of terminals input terminals and output terminals Figure 3 5 shows an example for such these terminals Usually the terminals on the left side are input terminals and the terminal on the right side are output terminals 25 OUTPUT mput
78. or a bulk superconductor the levitation force is dependent on many parameters such as the critical current density and grain size grain boundaries and orientations thickness of the sample and the critical superconducting parameters of the sample For a magnet the levitation force is closely related with the magnetic flux density magnetic field distribution The low levitation force of sample without nanoparticle inclusions can be attributed to two intrinsic material problems of a superconductor The first is the grain boundary weak link problem and the second is the weak flux pinning problem In order to resolve these two problems we have prepared different samples using different material processing techniques such as melt texturing nanoparticles addition irradiation and chemical solution deposition method 37 40 Our previous results shows that the critical current density which is directly related to the pinning force can be drastically enhanced due to 89 nanoparticles inclusions and irradiation 28 38 YBCO AI 03 MgB t CeO ion irradiation We have noticed that by increasing the pinning sites by nanoparticles addition in our sample the levitation force increases by about ten times at distances quite close to the magnet surface 2mm 90 Chapter Seven Conclusions An automated advanced physics experiments have been established at the magnetic measurements and superconductivity laboratory physics department The programm
79. pecific start or stop action from the user The user just clicks the Run button You can convert these simple VIs into subVIs that you use as building blocks for larger applications Figure 3 7 a displays the block diagram of the simple VI architecture for determining the warning level This VI performs 28 a single task it determines what warning to output dependent on a set of inputs You can use this VI as a subVI whenever you must determine the warning level Note that this VI contains no start or stop actions from the user In this VI all block diagram objects are connected through dataflow You can determine the overall order of operations by following the flow of data For example the Not Equal function cannot execute until the Greater Than or Equal the Less Than or Equal and both Select functions have executed 3 5 2 General VI Design Patterns A general VI design pattern has three main phases Each phase may contain code that follows another type of design pattern The three main phases include the following Startup This phase initializes hardware reads configuration information from files or prompts the user for data file locations Main Application This phase consists of at least one loop that repeats until the user decides to exit the program or the program terminates for other reasons such as I O completion Shutdown This phase closes files writes configuration information to disk or resets I O to the default state Figure 3 7 a
80. produce filters with extraordinarily steep skirts extremely rapid fall off in transmission outside the band of interest or to produce filters that are extremely narrow in bandwidth In either case such filters can still have very low insertion losses Figure 2 11 shows the measured response of an HTS filter designed for the wideband CDMA spectrum near 1 9 GHz CI E a pat E n 109535 LELE E Frequency MHz Figure 2 11 Wideband high Tc superconductor filter measured data The attenuation in this filter is such that the rejection reaches 100 dB only 400 MHz from the band edge Such a filter would be virtually impossible to make using conventional approaches and in any case would have enormous losses 1f it were built at all 19 Chapter Three LabVIEW for Automated Test and Measurement 3 1 What is LabVIEW LabVIEW Labortary Virtual Instrument Engieering Workbench is a graphical programming language that is manufactured by National Instruments and is typically used to automate data acquisition in research labs and industry 3 To accompany the software corresponding hardware must also be installed Within the central processing unit of a computer a General Purpose Interfacing Bus GPIB card 1s installed into the PCI slot The GPIB card is the connection between GPIB compatible instrumentation and the computer The card uses handshaking to communicate between talkers listeners and t
81. quencies passed by a filter is known as the filter s passband Since the amplitude response curve of this filter is fairly smooth there are no obvious boundaries for the passband Often the passband limits will be defined by system requirements A system may require for example that the gain variation between 400 Hz and 1 5 kHz be less than 1 dB as shown in Figure 4 6 b This specification would effectively define the passband as 400 Hz to 1 5 kHz In other cases though we may be presented with a transfer function with no passband limits specified In this case and in any other case with no 39 explicit passband limits the passband limits are usually assumed to be the frequencies where the gain has dropped by 3 decibels to or 0 707 of its maximum voltage gain 23 These frequencies are therefore called the 3 dB frequencies or the cutoff frequencies However if a passband gain variation 1 e 1 dB is specified the cutoff frequencies will be the frequencies at which the maximum gain variation specification 1s exceeded E ACHO i 3 i t d 7 E E i TER rs EPE a Alternate a z u Ha ea u CTET E o a i 10k oh aJa LJ a a 2k ohm a ee DIU ay OU ae CH nung a mere waa eee NI ELWS Oscilloscope 7 NATIONAL NSTRUMENTS INSTRUMENTS Figure 4 6 Figure a The electronic circuit for the banpass filter b Amplitude and phas
82. r reading you want to sweep so it calculates its current step and limit the maximum voltage by determining the compliance voltage In addition you are able to change several parameters such as the value of arm count trigger delay source delay and NPLC As soon as the device complete its sweep the I V curve is plotted in the graph tab where you have other related options for the scale and design Also the data record is visible so you can check or save it to an excel sheet in order to do other analysis 69 Figure 5 10 Experiment set up 70 Gens Saure Setup Linear Stair Sweep Source I Range Start I Stop I PointsStep 1 fioo ma 20000 3 Wooa Moo Borsa Compliance Asm Count NPLC Trig Delay 5 Sour Delayis 10 000 i Eoo go oon Currork TEMP K baam Io Figure 5 12 part of tempe Controller with I V sweep vi block diagram 71 Other important study for superconductor is to plot its Resistance Temperature Curves where you can see obviously the superconductivity phonemon and get easily the critical temperature For this purpose we designed our own program to acquire and plot the R T curve we think that the most exciting thing is to see the resistance drops suddenly to zero within small time intervals change so we constructed a real time plot In this program we merged the lakeshore331S and keithely2425 into one graph so they can work simultaneously as you see in F
83. rammed with Through this the PLC can tell the machine to stop functioning in case of a system overload that the temperature controller cannot handle 62 For the most basic case the temperature controller is stand alone and has no backup system This is mainly incorporated into systems that do not pose a hazard if overloaded and will not damage any expensive equipment 5 5 2 Types of Feedback Control All the graphs shown in this section use parameter values for the thermal model that are typical of a small domestic cooker and the set point temperature T is indicated by the red lines A On Off Control This is the simplest form of control used by almost all domestic thermostats When the oven is cooler than the set point temperature the heater is turned on at maximum power M and once the oven is hotter than the set point temperature the heater is switched off completely The turn on and turn off temperatures are deliberately made to differ by a small amount known as the hysteresis H to prevent noise from switching the heater rapidly and unnecessarily when the temperature is near the set point The fluctuations in temperature shown on the graph are significantly larger than the hysteresis as can be confirmed with the interactive simulation due to the significant heat capacity of the heating element B Proportional Control A proportional controller attempts to perform better than the On Off type by applying power W to th
84. ration of the basic and advanced physics of these experiments We will present examples of our virtual instruments magneto transport experimental set ups for low and high temperatures collected data sets and experimental results The main focus of this work is to study the current voltage characteristics resistance temperature measurements and the magnetic levitation force of YBCO high temperature superconductors The temperature dependence of I V characteristics and R T curves for YBCO samples have been investigated using four probe method The magnetic levitation force for a magnet magnet and superconductor magnet systems have been also studied The results were compared and discussed in terms of the relation between the critical current density and the pinning force in a superconductor Chapter One Introduction The processing and characterization of new or unconventional materials and devices used in high tech industrial applications makes use of automated equipment for each single step in processing and characterization techniques These techniques use stand alone equipment with built in microprocessors or application of specific microcontrollers which are hardcoded or programmed to accomplish that particular process If equipment for another process has to be automated then again a process of designing an entire stand alone system takes place The disadvantages of using such systems are they are expensive to manufacture it consumes a lot of t
85. rature superconductivity in a new class of ceramic materials in 1986 More precisely they found evidence for superconductivity around 40 K in Lay Mx CuO M Ba or Sr ceramic Bednorz and Muller s discovery was the result of several years of extensive investigations on metal oxides some of which had earlier been shown to be superconducting It is noteworthy that superconductivity in oxides had been known for many years but with very low T The end of 1986 and the beginning of 1987 were marked by synthesis of rare earth metal oxides with the discovery of the YBazCu307 YBCO superconductor with a Te of 93 K 14 The perovskite ABO3 structure of YBCO is shown in Figure 2 5 This was a significant breakthrough as it meant that for the first time the world has witnessed the existence of a superconductor with a Tc above that of liquid nitrogen boiling point 77 K which is much more abundant than helium much less expensive and liquid nitrogen cryogenic systems are less complex than systems using helium refrigeration The ease of making Y Bay Cus O7 ceramics by mixing calcining and oxidizing the constituent powders permitted its investigation by many laboratories of the world Early in 1988 Bismuth Bi and Tl cuprate oxides were discovered with Te 110 and 125 K respectively 15 16 These new HTSC containing Bi and Tl may have some advantages over ceramic superconductors containing rare earths Since the critical current density increases as T
86. rce on levitation gap for YBCO sample ZFC without nano pinning sites ad decreasing distance T increasing distance 25 15 Z mm Figure 6 10 Dependencies of levitation force on levitation gap for YBCO sample ZFC with nano pinning sites 88 Due to the magnetic stress between the trapped field in the sample and the magnet an attractive force occurs in the sample with nano pinning sites as in figure 6 10 When the sample is moved away from the magnet A small negative force appears at the bottom of the force curve This result can be attributed to the number of pinning centers in the sample which results in an increase of trapped magnetic field inside the samples In addition the levitation force is a function of the grain size and crystallographic orientation Moreover the weak links and cracks present in samples result in a small levitation force It can be seen in all case that the interaction force between the superconductor and the magnet always shows a hysteresis loop during the descending and ascending process This corresponds to the magnetization of the superconductor by mechanically moving the magnet or the superconductor toward and away from each other This interaction force was generated from the interaction between the magnetic field and the induced current in the superconductor The force is mainly dependent on the microstructure properties of the superconductor and the magnetic field distribution of the magnet F
87. re and software system that can be easily understood and modified LabVIEW can command DAQ boards in the computer to read analog input signals A D conversion generate analog output signals D A conversion read and write digital signals So using a data acquisition system and generic LabVIEW code that can be easy modified automation of equipment for any process can be implemented instead of using embedded devices and stand alone automation 1 3 The advantages of such a generic approach are that system monitoring and control are easier to understand and modify because of LabVEW s flexibility and ease of programming Excellent control can still be maintained over process parameters because of the real time feedback control system This system can be implemented without losing the integrity and the safety parameters of the equipment Using LabVIEW controlled DAQ system for automation has been realized and implemented on several devices available in our labs which are used for characterization of semiconductors superconductors polymers magnetic materials and nanomaterials In addition we have also tested several devices available in the electronic workshop and digital electronic lab used for educational purposes for undergraduate students using NI ELVIS provided from National Instruments 4 6 In this work the main emphasis was on building a LabVIEW controlled and automated set up for studying the magneto transport properties of YBCO super
88. reason manufacturers of temperature controllers soon started producing units that auto tuned This was an incredible time and labor saving creation because all it took to tune the new controllers was to set it up in the environment and let it run and decide the right PID variables for the process by itself The way it does this is shown in figure below AUTOTINe Ato Ttune Begins Llomplete OO Seat e Foint 5 180 fo cD agti of E 100 Set Point rans k Time Figure 5 6 Temperature versus Time Auto tuning The temperature controller starts out by putting the heater or cooling device on full power until it reaches 90 of the set point It does this to determine how fast the heating or cooling device works so that it does not overshoot the set point 30 As soon as it reaches 90 it begins to back off the power proportionally to what it has learned about the heating or cooling device and watches how fast the temperature drops when it shuts off the device This is important for it to decide when and how much power to cut when the process gets near the set point 61 After this the auto tuning is complete and the temperature controller decides on reasonable values for the PID This is usually not the end of the process however as an operator still has to come in and fine tune the PID values to make sure the process is operating at an optimal level Other situations however are less demanding and require only the a
89. rs is on YBCO The reason so much effort has been put forth on researching and applying YBCO superconductors rather than alternative high temperature superconductors HTSC is because it has some of the best superconducting properties and offers the potential for lower cost products repeated from the third page on the introduction Zero resistance and high current density have a major impact on electric power transmission and also enable much smaller or more powerful magnets for motors generators energy storage medical equipment and industrial separations Low resistance at high frequencies and extremely low signal dispersion are key aspects in microwave 11 components communications technology and several military applications Low resistance at higher frequencies also reduces substantially the challenges inherent to miniaturization brought about by resistive or I R heating The high sensitivity of superconductors to magnetic field provides a unique sensing capability in many cases 1000x superior to today s best conventional measurement technology Magnetic field exclusion is important in multi layer electronic component miniaturization provides a mechanism for magnetic levitation and enables magnetic field containment of charged particles In addition to trying to develop new HTSC materials researchers were also trying to fabricate materials with improved critical current densities Jc Current densities as high as 10 10 A cm
90. s Prototyping Board 4 1 4 NI ELVIS Functions 4 2 NI ELVIS Band Pass Filter 4 3 GPIB 488 2 4 3 1 GPIB Signals 4 3 2 Types of Messages 4 3 3 Talkers Listeners and Controllers 4 3 4 Restrictions 4 4 LF Impedence Analyzer Chapter Five Experimental Set Up 5 1 Characteristic and Resistivity Measurement 5 2 The Linear Four Probe Method 5 3 Measurements procedure 5 4 PID Propotional Integral Dervative Temperature Controller 5 4 1 PID Control and its use with temperature 5 5 tuning a temperature controller 5 5 1 Types Of Temperature Controller 5 5 2 Types of Feedback Control 5 5 3 Third Order Systems 5 6 Sources of Error and Measurement Considerations 5 7 I V and R T programs 5 8 Levitation Force 5 8 1 Levitation force Measurements Set Up Chapter Six Results and Discussions 6 1 Sample preparation 6 2 Resistance Temperature Measurements 35 35 36 38 41 42 43 43 44 44 52 52 54 57 58 59 60 62 63 66 66 68 73 75 79 79 80 6 3 I V Characteristics 6 4 Magnet Magnet Levitation force 6 5 Superconductor Magnet Levitation Force Chapter Seven Conclusions References Arabic Abstract 83 86 87 91 94 97 Figure 2 1 22 4 7 a 4 7 b 4 8 4 9 4 10 4 11 4 12 4 13 4 14 5 1 a2 LIST OF FIGURES DESCRIPTION Temperature dependence of the resistance for normal and superconducting states Illustration of the functional dependence of the
91. s schematically the boundary in temperature magnetic field and current density space separating normal and superconducting states The position of this boundary will of course depend on the material For temperature magnetic field and current density values lying between the origin and this boundary the material will be a superconductive outside the boundary conductions is normal The discovery and development in the 1950s and 1960s of superconductors which can remain superconducting at much higher fields and currents lead to the production of useful superconducting magnets Abrikosov in 1957 studied the behaviour of superconductors in an external magnetic field and discovered that one can distinguish two types of materials type I and type II superconductors 10 While type I expels magnetic flux completely from its interior type II does it completely only at small fields and partially at higher external fields Thus due to the formation of the mixed state these materials can sustain superconductivity even in higher magnetic fields higher than 10 Tesla Type Il superconductors are therefore the ones that are of interest for most large scale applications Such high magnetic field and large current carrying capability superconductors which exhibits two critical fields Hc and Hc2 are called hard or type II superconductors They passes from the perfect diamagnetic state at low magnetic fields to a mixed state and finally to a she
92. s way of doing science at high and well organized levels I produce my deep thanks to the committee members Dr Maen Gharaibeh and Dr Abdul Raouf Al Dairy I have the honor to discuss with them my thesis and receive their comments Special thanks to Eng Hazem Al Rashaideh for his technical support and suggestion to have a complete work My thanks to all my proffessors and doctors in the applied physics department at J U S T specially Dr Hasan al Ghanem Dr Khalaf Abd Alazeez and Dr Mohammad Gharaibeh Finally I d like to say thanks to my friend Zeinab Ghadieh for supporting me through the research time TABLE OF CONTENTS Title DEDICATION ACKNOELDMENTS TABLE OF CONTENTS LIST OF FIGURES LIST OF TABLES ABSTRACT Chapter One Introduction Chapter Two Superconductivity 2 1 Brief History of Superconductivity 2 2 Applications of Superconductivity Chapter Three LabVIEW for Automated Test and Measurement 3 1 What is LabVIEW 3 2 LabVIEW Program 3 3 Programming by LabVIEW 3 4 Virtual Instrumentation 3 5 Examples of Virtual Instruments Vis 3 5 1 Simple VI Design Patterns 3 5 2 General VI Design Patterns 3 6 Parallelism 3 7 Instrument I O 3 8 Data Acquisition Chapter Four Selected Examples on Interfacing Using LabVIEW 4 1 NI ELVIS I 4 1 1 Applications Page iii vi viii 11 20 20 21 23 27 28 28 29 30 31 32 33 33 34 4 1 2 NI ELVIS II Benchtop Workstation 4 1 3 NI ELVIS II Serie
93. sen and H Bratsberg Theory for lateral stability and magnetic stiffness in a high Tc superconductor magnet levitation system J Appl Phys 1993 74 4060 Bean C P Magnetization of Hard Superconductors Phys Rev Lett 1962 8 250 Albiss B A and I M Obaidat Applications of YBCO coated conductors a focus on the chemical solution deposition method J Mater Chem 2009 20 1836 1845 Gharaibeh M Albiss B A Jumah I and Obaidat I M Effective incorporation of nanoceria into polycrystalline MgBo J Appl Phys 2010 107 1 Albiss B A Al Rawashdeh N Alaa Abu Jabal Gharaibeh M Obaidat I M Polycrystalline YBa2Cu307 0 with Nano sized Al203 Inclusions Journal of Superconductivity and Novel Magnetism 2010 1557 1939 Obaidat I M Goeckner H P Albiss B A Kouvel J S Point and extended defects in superconductors Crystal Research and Technology 2008 43 8 837 844 96 Lae y aladtuls dale gall Ai 18 al gall Aeusbslicall 5 Ail Sll al gall asl LabVIEW Aaa d gene gaa illh aael gaki Lge i ely ill Aal a 4 aliil g Abc Lal diall ai oi 28 s L paal Cad FU g i gall Lin ol ail oyl JSin aasia il LabVIEW iam y ahaiuh iaaii ehy jill G let Gps gll aidb iall Jaa Lid al BY Saill g Ual B61 al alls 5 ieil aul rgall Javan Jis pill i 8 pill 3 eal Jua si inal sy 3 jee LabVIEW alaiul ai aal A ili ilal Jaai jea PID ehaill 3 pall dea 8 Sail Slew olal fell gi HU il NI ELVIS II 455 5 iulua cgl ga g GI
94. shows a simple VI Architecture and Figure 3 7 b shows the general VI design pattern Freeze Warming Wait Until Next ms Multiple Warning Text Start Up vi Current Temp Shut Down vi Place Code Here warning Figure 3 7 a Simple VI Architecture Figure3 7 b General VI Design Pattern In Figure 3 7 b the error cluster wires control the execution order of the three sections The While Loop does not execute until the Start Up VI finishes running and returns the error 29 cluster Consequently the Shut Down VI cannot run until the main program in the While Loop finishes and the error cluster data leaves the loop Most loops require a Wait function especially if that loop monitors user input on the front panel Without the Wait function the loop might run continuously and use all of the computer system resources The Wait function forces the loop to run asynchronously even if you specify 0 milliseconds as the wait period If the operations inside the main loop react to user inputs you can increase the wait period to a level acceptable for reaction times A wait of 100 200 ms is usually good because most users cannot detect that amount of delay between clicking a button on the front panel and the subsequent event execution For simple applications the main application loop is obvious and contains code that follows the Simple VI design pattern When the program includes complicated user interfaces or multiple tasks
95. sistance The sample surface was connected with four leads the two outermost leads are for the current and the two inner leads for voltage Good contacts are obtained necessary by measuring the surface resistance between any two of the four probes several Ohms enough to make good contacts The sample holder was entered inside the cryostat and the cryostat was closed tightly The vacuum pump was turned on for one hour or more before starting the cooling process to insure good vacuum to get a perfect cooling control and to prevent the formation of condensation on the sample surface with cooling The other instruments temperature controller the programmable current voltage Source Meter were also switched on one hour before for warming period 57 10 11 A current was applied by the current source manually in two directions and measuring the corresponding voltage at room temperature to make sure that linear relationship the sample is Ohmic in its normal state Liquid nitrogen was poured slowly through the fill funnel to start cooling after one hour the temperature reaches 78 K the lowest temperature reached in our LN2 cryostat Cooling rate was controlled carefully using the temperature controller The temperature controller was used to set the desired temperature we waited for 10 minutes after reaching the desired temperature Before starting measurements to insure temperature stability inside the cryostat At ea
96. ssociated with proportional control it does not cure the problem with the steady state error Fortunately it is possible to eliminate this while using relatively low gain by adding an integral term to the control function 176 lve Temperature C 170 oO SO 100 150 O0 z50 300 Time 33 Figure 5 9 Relation between temperature and generated power as a function of time Figure 5 9 shows that as expected adding the integral term has eliminated the steady state error The slight undershoot in the power suggests that there may be scope for further tweaking e Proportional Integral Control Sometimes particularly when the sensor measuring the oven temperature 1s susceptible to noise or other electrical interference derivative action can cause the heater power to fluctuate wildly In these circumstances it is often sensible use a PI controller or set the derivative action of a PID controller to zero 30 65 5 5 3 Third Order Systems Systems controlled using an integral action controller are almost always at least third order Unlike second order systems third order systems are fairly uncommon in physics but the methods of control theory make the analysis quite straightforward For instance applying the so called Routh Hurwitz stability criterion which is a systematic way of classifying the complex roots of the auxiliary equation for the model it can be shown that provided the integral gain is kept sufficiently sma
97. start its sweep displaying the frequencies and the parameters corresponding to them data will be recorded at LabVIEW table where you have the choice to save the data to Excel file analyze it do another sweep or back to home page In the analyze page you will get the following parameters Z Z E E M and M The relations between the raw data and pervious parameters are defined below with equations set 1 the curves Z versus Z Z Z versus log frequency E versus E E E versus log frequency and M versus M M M versus log frequency can also be obtained 27 The front panel for Analyze Data page seen in figure 4 13 z 4 zo i 2 2 422 2422 _ EA e D e 65 7 peace 1 W w j T O etped you can also save the new parameters to excel sheet and save images for the plots you get the whole options for impedance analyzer VI explained simply in the flow chart that shown in figure 4 14 48 Run amp Acquire Data SE SE E eg N N MM S ate pp PPP EE TE ET EEA d mE S tH J i Bele Finfo E Jsf ufu afeSahahehe se5s TT J Aah De tod ed ital fat Lat Rd al tel ttl teal al Men pejang tat Med tl ed Gol fel el kt tel tal Mel Ml Gol hel at Gol ted tal ek tl fe tool Lead ad SOUL ffp Function faf Start reg He Stop Frey T Step freg HE m eet eet deel tll elena iee iaeii
98. t were sintered and annealed in flowing oxygen for 6 h Finally the furnace was turned off and allowed to cool to room temperature The finished pellets were found to be black and very hard to break Figure 6 1 shows a representative schematic diagram of the sample preparation 79 Weighing Addition of Al O nanoparticles Grinding Lh Mixing amp grinding 2h Grinding ih Pelletization Pressure 10 tons Ventilate 500 C Lh Calcination 850 C 10h Final sintering 950 C 10h Oxygen flow 550 C 6 h Figure 6 1 Sample preparation procedures 6 2 Resistance Temperature Measurements The critical temperature T is one of the basic characteristics of the superconducting state It is determined as a standard by means of transport measurement of dependence of electric resistance R or resistivity on temperature T during the transition of sample from the normal to the superconducting state However various other methods are used e g inductance and magnetic but the question of their compatibility is still open The four point measurement technique of the R vs T dependence is the best known standard method for the determination of various characteristics of superconducting and normal states of superconductors The critical temperature Tc R 0 and the transition width ATc R 0 characterized by various criteria are the best known from these characteristics In bulk and polycrystalline superconductors the tra
99. t point The integral part of PID control eliminates this The controller output is proportional to the amount of time the error is present C Derivative The third system working in a PID controller is the derivative control The derivative control affects the system by increasing stability and by reducing the overshoot and undershoot of the function and improving transient response The output under derivative control is proportional to the rate of change of the error over time This part of the control system 1s critical because in some processes an overshoot in temperature might cause a part or machine to be damaged controller reads the resistance of the wire and correlates it to a temperature listed for that resistance that is programmed into the controller 5 5 TUNING A TEMPERATURE CONTROLLER Tuning the PID system on a temperature controller was not an easy task by any means in the earlier years of PID temperature control It involved setting up the system configuring it to how you best thought it might need and guessing what parameters the PID system 60 should use for the operation This was more than tedious for a worker to do and sometimes took days on more complicated temperature systems 30 This was because a temperature system is one of the more complicated systems to model for PID control There are numerous variables that are nearly impossible to simulate versus how they behave in the real world For this
100. termine exactly the value of the current and the corresponding voltage Vc at which the sample becomes non superconducting because of the soft knee in the I V curves of HTSCs D D 2 0 4 0 6 OW 1 1 Tr Figure 6 5 Example of I V curves for the pure YBCO sample with different contacts using silver epoxy The good and bad contacts are indicated A different choice of Vc results in a different value of Ic There are various ways to determine Ic using different voltage criteria Figure 6 6 the easy way is to increase the 84 current steadily until the first reading of the voltage at I Ic 33 another way is to draw the tangent of the I V curve in the high current range and the intersection of this tangent with the current axis is considered to be the critical current I Ico In our measurements we have chosen a voltage criterion Vc 10 uV and we considered the corresponding current value to be the critical current I Ic3 Figure 6 7 shows a typical I V characteristics for the YBCO sample at zero applied magnetic field A gradual decrease of the critical current density Jc of the sample have been observed with increasing the temperature close to the critical temperature of the sample which is about 92 K This experiment was done using the current source with a maximum current limit of 3 A Several experiments were done for other samples with extremely high critical current densities higher than 3 A which is beyond the current limits
101. ting sample the separation distance between the superconductor and the small magnet 5 8 1 Levitation force Measurements Set Up We present here experiments to analyze in a quantitative way the levitation phenomena and the free suspension counterpart both resulting from the interaction of a superconducting sample with a permanent magnet The analysis is done by measuring the interaction force between a HTS and the magnet by means of an electronic balance when the HTS is cycled in the magnet s field In spite of the requirement of cryogenic liquid for cooling the samples below Tc it is not necessary to control temperature and then using a 75 cryostat is not imperative Since experiments use conventional elements easily found in educational laboratories they are implemented with no difficulty and with a minimum cost After introducing the main properties of superconducting materials and the concept of magnetic levitation and suspension associated with them we will describe the experimental array and the measurements will be shown and discussed Levitation or free suspension of a body is possible if a force acts against gravity compensating the body s weight Levitation may be attained by different methods by a jet of air by acoustic pressure etc although free suspension is somewhat more exotic Stability is the main problem in the two cases This condition however is fulfilled in the case of type II superconductors interacting
102. uto tuning of the controller for safe and optimal operation Most of the time the only problem with the temperature controllers auto tuning settings is a slight overshoot in the final temperature This can be adjusted down by simply changing the value of the integral in the PID control Most contemporary PID controllers come with an easy to use interface that can be learned in a couple of hours The earlier models were not so easy to use and tuning a temperature controller usually involved bringing in a representative from the company for a day to teach few maintenances and engineering workers how to set and adjust the controllers 5 5 1 Types of Temperature Controllers Temperature controllers come equipped with a number of different options Deciding on a temperature controller has a lot to do with the inputs and outputs but there are also other features that they can utilize that are not necessary for all operations Temperature controllers can be used in either a stand alone operation or can be run with a programmable logic controller or PLC The more complicated operations usually have the temperature controllers hooked up to a main communications bus that can be monitored from any part of the installation A step down from this system is a temperature controller simply hooked up to a stand alone PLC In this fashion the PLC takes the temperature controller set point as an input and any alarms that the temperature controller might be prog

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