Borehole X-Ray Fluorescence Spectrometer (XRFS): User`s Manual
Contents
1. BLA C 8192Ch 2048Ch C 512Ch nd C 4096Ch C 1024Ch 256Ch C uw USB Jd AutoBaseline Rise Time Discrimination i oe Save Configuration Slow C On RTD threshold 59 FS C Off gt Off RTD Fast HWHM 12 Recall Configuration Testpoint 5 zi c Count Delta Total Figure 9 View of configuration setting load DP4 configuration panel 11 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Borehole XRFS Software Installation Before connecting hardware copy all files from CD R folder titled BoreholeXRF As Shipped Bin Sept 27 2007 Place files in C Program Files BoreholeXRF Note the files MUST be in exactly this location to operate correctly Necessary software files from the folder BoreholeXRF As Shipped Bin Sept 27 2007 e xrayxsct dat XRFanalysis dll e APL UW XraySettings xcg 1 BoreholeXRF exe e cbw32 dll e COMCAT DLL e COMCT232 0CX e Comdlg32 ocx e dp4 cfg MSCOMM32 0CX e msvbvm60 dll 1 1 e usbdrvd dll Install the driver for the Measurement Computing DAQ module Load the Measurement Computing MCC DAQ Software CD Install InstaCal for Windows TracerDAQ and Hadware manuals e Install Shield Wizard for InstaCal click Next Destination Folder click Next TR 0703 12 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY e Ready to Install click Install e Comple2. m Fe Int Norm Fe Int 0 02 Fraction Change o 0 04 0 06 0 08 0 1 0 1 2 3 4 5 Distance mm 0 2 gt Fraction Change 0 10 20 30 Distance mm Figure 18 Variation in fractional change of total spectrum counts and iron intensity with distance to probe Tests conducted with SRM 2711 Note different scales TR 0703 48 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY The results of varying the distance from the probe to the sample are given in Figure 18 The intensity in the iron peak and the total counts in the spectrum are plotted as a function of separation between the probe body and the sample surface The plot on the left shows the behavior in the first few millimeters and the plot on the right shows all of the data taken for this test Note that both of these measurements are stable to within 296 for as much as 2 mm of separation In addition the normalized iron intensity which is the ratio of the iron peak to the total counts is plotted as the green line This quantity is stable out to almost 5 mm indicating that accurate quantitation can be performed even at this distance This is important since the diameter of the borehole may not be constant and thus the distance between the probe and the regolith being measured may vary Because of the design these expected variations will not affect the results of they are less than 2 mm and can be compensate
3. Send comments regarding this burden estimate or any other aspect of this collection of information including suggestions for reducing this burden to Washington Headquarters Services Directorate for Information Operations and Reports 1215 Jefferson Davis Highway Suite 1204 Arlington VA 22202 4302 and to the Office of Information and Regulatory Affairs Office of Management and Budget Washington DC 20503 1 AGENCY USE ONLY Leave blank 2 REPORT DATE 3 REPORT TYPE AND DATES COVERED December 2007 Technical Report 4 TITLE AND SUBTITLE 5 FUNDING NUMBERS Borehole X Ray Fluorescence Spectrometer XRFS User s Manual NNL05AA49C Software Description and Performance Report AUTHOR S W C Kelliher I A Carlberg W T Elam and E Willard Schmoe PERFORMING ORGANIZATION NAME S AND ADDRESS ES 8 PERFORMING ORGANIZATION REPORT NUMBER Applied Physics Laboratory University of Washington APL UW TR 0703 1013 NE 40th Street Seattle WA 98105 6698 SPONSORING MONITORING AGENCY NAME S AND ADDRESS ES 10 SPONSORING MONITORING Cedric Mitchener AGENCY REPORT NUMBER Office of Procurement Research amp Projects Contracting Branch Mail Stop 126 9B Langley Blvd Hampton VA 23681 2199 SUPPLEMENTARY NOTES 12a DISTRIBUTION AVAILABILITY STATEMENT 12b DISTRIBUTION CODE Approved for public release distribution is unlimited 13 ABSTRACT Maximum 200 words The X ray fluorescence spectrometer XRFS is designed to
4. This module calls another written in C to handle all of the computations The parameters needed by the physical model contained in the code are provided by the spectrum processing module to the C module The results of the spectrum analysis are provided to the user in an on screen list and to the spectrum display module This includes the calculated background and peak fits the list of elements found in the spectrum and the weight fractions of each element with associated uncertainties Figure 7 Net intensities of the associated peaks for each element are also displayed with the intensity error from the Poisson statistics of the spectrum in the list on the lower right corner of the interface The element identification and association of peaks with elements is fully automated but is not entirely reliable The quantitative results can be copied to the clipboard and made available outside the program to prepare reports using the results of this instrument Functions Background calculation and removal Peak search Element identification associate peaks with elements Net peak intensity determination and calculated peak fits Quantitative analysis converting peak intensity to element weight percent Copy results to display Spectrum Display SD Functions Plot spectrum vs X ray energy Figure 5 Overlay calculated background and peak fits TR 0703 36 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Display markers
5. measured in the Mars simulated atmosphere The silver target X ray tube was operated at 35 kV and 2 uA No filters or other optics were used in the incident beam The detector has an internal collimator to restrict the beam to the center of the diode Data collection time was 1000 sec for the upper spectrum and 100 sec for the lower spectrum Note that the majority of the information 15 still available even with the 100 sec data collection time This short data collection will greatly facilitate the measurement of multiple strata in a borehole with vertical resolution of about 1 cm 1 000 000 4 100 000 un 4 o 10 000 1 000 0 5 10 15 20 25 30 Energy keV Figure 14 Spectra from borehole XRF spectrometer Upper curve is 1000 sec data collection time and lower curve is 100 sec TR 0703 42 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY As a comparison the APXS alpha proton X ray spectrometer spectra used on the Pathfinder and MER rovers have little usable data above the iron peaks at 6 4 keV Figure 15 The spectrum acquisition times for both APXS curves were many hours The scale is counts per second so 1 corresponds to about 72 000 total counts 10 MER 20 hours MPF 70 hours 0 1 Counts s 30eV 1E 3 2000 4000 6000 8000 10000 12000 14000 16000 Energy eV Figure 15 Spectra from the APXS instrument Reproduced with permission Detection li
6. yes Extinterlock SW connect closed Extinterlock SW status Spectrum analysis Results Elem Err Int Si 51 9205 2 3543 Rb 0 1577 4 3147 2 5 8 3675 1 16354 104 Cd 0 3543 7 1809 2 0 Ca 11 5213 1 29568 0 Sn 0 6938 6 2110 d 15 Ti 1 3978 2 pens id 5 Fe 19 1297 1 20902 t 1 0 rete Eu 1 0360 3 6000 lt cursor cursor gt Tb 2 7611 2 18367 3 0 5 Cu 0 0435 17 548 0 0 i in out gt 0 5 10 15 20 25 30 35 40 Cursor Energy 18 80259 Save 5 ay countsz 715 Spectrum Exit Figure 7 View of spectrum analysis display TR 0703 10 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Select parameter to change 2 Edit to change value uA Setting 20 kV Input Scale Input Offset uA Input Scale uA Input Offset uA Divider gigaOhm Output Scale Output Offset uA Output Scale uA Output Offset Ramp Interval sec kv Ramp Delta uA Ramp Delta Filament Start kV Limit uA Limit anode z Path Atmosphere 12V ac 2 He 3 Mars 4 3 C02 He 5 E arth Window Type 1 Boron Carbide 2 Plastic Figure 8 View of configuration setting load parameters panel Amptek PX4 DP4 Digital Pulse Processor Time to Peak Top Width Threshold ast Threshold utput Offset 41 Preset Time 12 8u5 5 uS 5exrs 13 10m b s DAC BLR OFF 0 Buffer Select PUR Reset FastCh Decimated c Port On Shaped
7. WASHINGTON APPLIED PHYSICS LABORATORY Completing installation click Finish Run the InstaCal program From the menu bar select Start lt Programs gt Measurement Computing lt Instacal e Plug and Play Board Detection USB 1408FS Serial 150 should be selected Click OK Under the Install menu item choose Configure e Change No of Channels from 4 Differential to 8 Single Ended Click OK e Under the File menu item choose Exit Run the Borehole XRF program by double clicking on the file Borehole At this point the software main screen should appear it will obtain a spectrum and bring up all dialogs You may want to put a shortcut to the Borehole XRF exe file on the desktop or some other convenient location TR 0703 14 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Instrument Design The instrument is designed to be deployed down a pre drilled borehole and has a maximum diameter of 27 1 mm to be compatible with existing drills Figure 1 and Figure 10 The XRFS sensor assembly consists of an XRFS enclosed head assembly that is deployed down the borehole and an electronics control assembly consisting of a power supply and control electronics for the XRFS instrument PC based software provides the control data readout and quantitative calculations needed for interpretation of the XRFS spectra The excitation source is a sil
8. burned out The current detector does not provide a signal unless the lamp is energized a delay must be provided that allows the lamp to be turned on then X rays must be turned off if the current detector does not indicate lamp operation The delay is typically about 100 milliseconds Electrical interlock status Purpose An external signal provided by a user that indicates that all of the X ray shielding is in place Background Another federal safety requirement is that the enclosure that protects human operators from radiation exposure be interlocked to the high voltage supply This interlock must disable the high voltage if the shielding is opened to prevent accidental radiation exposure TR 0703 24 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Operation An external signal It disables the high voltage power supply and prevent X rays from being turned on or shut them off if they are on The signal is typically an external switch closure It also disables the X rays in case ofa short to ground to prevent shorts from giving a false OK signal A TTL or other logic signal is OK if 5 V or similar is available on the external connector to facilitate use with un powered mechanical switches on a radiation enclosure Filament connector engaged Purpose To insure that the filament connector is inserted before the high voltage or X rays are turned on Background The commercial miniature high voltage connector
9. function Set and display detector parameters Aperture size and distance Path length from specimen to detector Energy resolution Window material and thickness e Dead layer material and thickness Active layer material and thickness Angle that X rays exit specimen toward detector emergence angle Set and display digital pulse processor parameters e See manufacturer s manual Appendix A Control digital pulse processor setup Save and Load Parameters PAR Description This module handles all the parameters from other modules The functions in this module are called at startup and shutdown and by the other modules whenever any parameters are changed The module saves the parameters to a file and reads them from a file The name and location of the parameter file are set and displayed by this module via a dialog Figure 8 No other parameters are modified or displayed by this module The file format is determined and controlled by this module 33 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Functions Set and display parameter file name Save all parameters to file Load all parameters from file Save and Load Spectrum SSF Description The spectrum is stored in a file that contains the spectrum data counts per channel the energy calibration that relates channels to X ray energy the parameters under which it was acquired and the description of the instrument Older files can be
10. loop The output goes to a power audio amplifier chip to produce enough power and voltage to drive the filament transformer which is located in the XRF Head The feedback loop compares the current signal from the HV module to a set point and adjusts the filament heater voltage The feedback has upper and lower limits via a Zener diode integration of the error signal via a capacitor and some linear gain for stability via a resistor all in the feedback leg of an op amp This regulator reverts to the filament off condition on power up and wherever X rays are turned off Isolation and amplification of HV monitor signal APL UW Purpose To condition the signals from the HV module to achieve convenient gain and to protect the remainder of the circuits from spikes due to high voltage arcs Operation Op amps with diode and capacitor spike suppression at their inputs 27 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Over current cutoff APL UW Purpose To protect all of the hardware from a long term overload condition Background X ray tubes sometimes develop arcs or plasma discharges If they are brief they usually clear themselves and are not a problem But if they last for several seconds they can overheat themselves or other components This protection circuit serves as a backup to the software over current protection The HV module is also current limited but that only protects the module not th
11. A Input Scale 24 50000000 uAoffsetin uA Input Offset 0 01000000 uAdividerR uA Divider resistance gigaOhm 0 40500000 kVscaleOut kV Output Scale 0 09380000 kVoffsetOut kV Output Offset 0 14000000 uAscaleOut uA Output Scale 0 04100000 uAoffsetOut uA Output Offset 0 10000000 Rampilnterval Ramp Interval sec 1 00000000 kVdelta kV Ramp Delta 1 00000000 uAdelta uA Ramp Delta 5 00000000 kVstart Minimum kV for Filament Start 10 00000000 kVlimit kV Limit 40 00000000 uAlimit uA Limit 25 00000000 anode z X ray tube anode atomic number 47 00000000 kv X ray tube kiloVolts during acq 20 21008301 tube inc angle X ray tube electron incident angle 90 00000000 tube takeoff angle X ray tube takeoff angle 51 11999893 tube be window X ray tube Be window mm 0 50000000 filter z Incident beam Filter atomic number 1 00000000 filter thick Incident beam Filter thickness micron 0 00000000 excit angle Incident beam Excitation angle deg 38 86999893 emerg angle Fluorescence Emergence angle deg 74 12000275 solid angle Solid Angle sterdian 0 00000850 path type Atmosphere Path type 2 00000000 inc path length Incident path length cm 0 94000000 emerg path length Emergence path length cm 1 97000003 window type Probe Window type 2 00000000 window thick Probe Window thickness micron 0 00000000 minimum energy Minimum analysis energy eV 1000 00000000 35 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Spectrum Processing SP Description
12. Approved for public release distribution is unlimited Borehole X Ray Fluorescence Spectrometer XRFS User s Manual Software Description and Performance Report built by APL UW under a NASA contract from the Langley Research Center W C Kelliher I A Carlberg W T Elam and E Willard Schmoe 1 Langley Research Center Hampton VA Applied Physics Laboratory University of Washington Seattle Technical Report APL UW TR 0703 December 2007 Applied Physics Laboratory University of Washington 1013 NE 40th Street Seattle Washington 98105 6698 Contract NNLO5AA49C UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Acknowledgments This project was funded by NASA Headquarters as part of the Mars Technology Program Subsurface Access Task administered by the Jet Propulsion Laboratory We are indebted to the program managers Suparna Mukherjee and Chester Chu for their guidance The XRF spectrometer design and construction were performed by the Ocean Engineering Department of the Applied Physics Laboratory Russ Light Vern Miller Pete Sabin Fran Olson Tim Wen and Dan Stearns The performance reported here is due to their efforts The University of Washington effort was funded under NASA contract NNLOSAA49C i TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY TR 0703 ii UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Contents Users diano et oi
13. HINGTON APPLIED PHYSICS LABORATORY Quick Start Guide Figure 2 from left to right Borehole XRFS Head Unit X ray warning light umbilical cable X ray Interface and Control units and laptop computer Setup To set up the instrument 1 Remove the units from the case The instrument consists of the XRF Interface Unit the XRF Control Unit and the XRF Head Unit Figure 2 A laptop computer is used to control the instrument There are three cables connecting the Interface and Control units and the Head Unit has an umbilical cable 15 ft long permanently attached to connect it to the Control Unit An X ray warning light is also supplied The instrument must be used in a radiation safety enclosure TR 0703 2 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY or other personnel safety arrangement An interlock cable connects to the safety interlock switch on the radiation safety enclosure to prevent accidental exposure Connect the cables as shown in Figure 3 All cables must be connected before turning on the main power Connect USB cable to the laptop computer and turn on the instrument with the key switch The laptop should beep when it recognizes the connection to the instrument Wait one to two minutes for the detector to cool down The instrument is now ready to collect a spectrum 3 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY x 5 a gt 5 5 3 2 2
14. NIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY User s Manual Overview The X ray fluorescence spectrometer XRFS is designed to be deployed down a pre drilled hole for exploration and elemental analysis of subsurface planetary regolith Figure 2 and Figure 10 The spectrometer excites atoms in the regolith and causes them to emit their characteristic X rays These characteristic X rays produce peaks in the X ray spectrum By measuring the energy of the X rays elements are identified By measuring the intensity of the peaks the amount of each element can be determined A software package operates the spectrometer acquires the data and analyzes the spectrum to provide elements and their weight fractions It also provides a user interface to control the measurements and display the results Figure 1 X ray fluorescence spectrometer Head Unit designed to be deployed down a pre drilled hole to analyze subsurface elements The spectrometer consists of two main subsystems packaged in three physical units The main subsystems are the X ray source and the energy dispersive X ray detector The source provides the X rays to excite the specimen of regolith being investigated The energy dispersive X ray detector detects the emitted X rays determines their energy the energy dispersive function and counts the X rays at each energy Together these two subsystems measure the X ray spectrum of the specimen 1 TR 0703 UNIVERSITY OF WAS
15. an be obtained regardless of water content Also the presence of water will cause no significant degradation of detection limits The region of the spectrum that has peaks from coherent Rayleigh and incoherent Compon scatter from the characteristic emission lines of the silver X ray tube is shown in more detail in Figure 17 Note that the scatter is much larger in the saturated and frozen specimens This increased scatter indicates presence of water and can be used to quantify the amount of water present 45 TR 0703 90000 70000 60000 ity 50000 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Frozen 40000 X ray Intens 30000 20000 10000 Saturated 5 10 15 20 25 30 Energy keV Figure 16 Spectra of dry water saturated and frozen samples of SRM 2702 Frozen spectrum is 100 seconds to avoid thawing It is multiplied by 10 for comparison TR 0703 46 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY 5000 4500 4000 3500 3000 6 Dry Frozen Saturated 2500 2000 X ray Intensity 1500 1000 500 20 21 22 23 24 25 Energy keV Figure 17 Spectra of dry water saturated and frozen samples of SRM 2702 Frozen spectrum is 100 seconds to avoid thawing It is multiplied by 10 for comparison 47 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY 0 1 4 0 08 0 06 0 04 0 02 Total Counts
16. argument for using an X ray tube Measured power consumption is given in Table 3 for the system components and the total Ground support components including the safety interlocks and the USB computer interface are not included as these functions are either not necessary in a spacecraft or are expected to be provided The total power of 12 watts implies an energy requirement of 12 kJ per spectrum for a 1000 sec spectrum or 1200 J for a 100 sec spectrum This is comparable to the APXS energy per spectrum with larger power consumption but shorter collection times TR 0703 44 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Table 2 Minimum detection limits for several elements Element 2702 2709 2710 2711 97B Average Mg ND ND ND ND ND 14 Ni ND 8 9 2 0 ND NP 5 5 Cu 8 2 4 2 16 2 8 9 NP 9 4 Zn 8 0 6 6 16 9 8 3 6 4 9 2 Pb 8 8 3 3 22 0 12 4 NP 11 6 Zr NP 4 5 NP 4 1 4 8 4 5 ND Not Detected NP None Present Table 3 Power consumption during data collection Function Voltage Current Power HV Power Supply 14 84 0 426 6 31 W X ray tube control 14 92 0 150A 4 46W 14 92V 0 149 Detector 4 99 0 240 1 20 W Total 11 97 W The effect on the measured spectrum from the presence of water is shown in Figure 16 where spectra from dry water saturated and frozen specimens of SRM 2702 are overlaid There is almost no change in peak intensities which is expected and indicates that good quantitative information c
17. at characteristic element emission line energies Scale zoom and pan 37 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Instrument Performance Report The purpose of this instrument is elemental analysis of regolith strata in a pre drilled borehole to investigate the subsurface of Mars and possibly other bodies within the solar system As such the primary performance criterion is the ability to quantify the elements present in a particular stratum in an acceptable time and with sufficient accuracy to obtain useful scientific information For the purposes of this study the detailed performance of the sensor was evaluated by measurements on the actual prototype The main performance metric is the minimum detection limit MDL Improvements in the ability to detect an element imply improvements in the ability to quantify the amount present Though there are some subtleties in this the performance is dominated by the number of X rays present in the spectrum which is dominated by the source strength given the constraints on geometry and the available detectors for this instrument The performance was evaluated by measuring the detection limits of target elements in a light element matrix The ability to accurately quantify a particular element is mainly limited by the precision with which its X ray emissions can be measured This is determined by the statistical variations in X ray intensity due to the Poisson nature of t
18. be deployed down a pre drilled hole for exploration and elemental analysis of subsurface planetary regolith The spectrometer excites atoms in the regolith and causes them to emit their char acteristic X rays These characteristic X rays produce peaks in the X ray spectrum By measuring the energy of the X rays elements are identified By measuring the intensity of the peaks the amount of each element can be determined A software package operates the spectrometer acquires the data and analyzes the spectrum to provide elements and their weight fractions It also provides a user interface to control the measurements and display the results The spectrometer consists of two main subsystems packaged in three physical units The main subsystems are the X ray source and the energy dispersive X ray detector The source provides the X rays to excite the specimen of regolith being investigated The energy dispersive X ray detector detects the emitted X rays determines their energy the energy dispersive function and counts the X rays at each energy Together these two subsystems measure the X ray spectrum of the specimen SUBJECT TERMS 15 NUMBER OF PAGES Mars spectrometry regolith X ray fluorescence XRF elemental analysis inorganic analysis 57 CD R borehole 16 PRICE CODE SECURITY CLASSIFICATION 18 SECURITY CLASSIFICATION 19 SECURITY CLASSIFICATION 20 LIMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT Unclassified Unclassifi
19. before during or after spectrum collection To save the spectrum click Save 12 To determine which elements are present in the sample click the Analyze button After several seconds the plot box will show the background and spectrum fits and the elemental analysis will appear in the spectrum analysis box Figure 7 Software operation Configuration settings load params panel Figure 8 Opening this window allows the user to change instrument control parameters such as the ramp interval and acquisition conditions such as the atmosphere type 5 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY load DP4 config panel Figure 9 Opening this panel allows the setting for the DP4 digital pulse processor to be changed Refer to the AmpTek manual Appendix A on the DP4 for more information about these parameters and off under X ray control These buttons turn the X rays on and off setkV This button allows the user to set the high voltage for the X ray tube set LA This button allows the user to set the emission current change preset time Use this button to enter the desired interval of data collection in seconds then click OK This command automatically clears the spectrum that is currently plotted so save it first When the user clicks Start after entering this preset time the program will collect a spectrum and stop automatically after t
20. cquisition module is to check set and maintain the detector energy calibration Figure 6 This calibration relates the channels in the spectrum which are proportional to the pulse amplitude from the detector to X ray energy The calibration is determined using the peaks of known elements either in the spectrum from the material of interest if they are known or from a calibration sample The energy calibration procedure consists of finding the location of the peaks identifying the element associated with the peak and including the peak positions and element energies in a calibration function The function used is linear The energy calibration will usually not change much day to day so a stored calibration can be used Any changes in the DPP tuning will change the calibration so the DPP setup and calibration will force a re calibration if any DPP parameters are changed Functions Communicate with detector digital signal processor COTS code Set and display data acquisition parameters Live time seconds calculated in DPP Real time seconds Count rate counts per second display only e Dead time display only Total counts display only TR 0703 32 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Chamber atmosphere Earth ambient Mars ambient pure helium vacuum Energy calibration eV per spectrum channel e Set and display calibration constants Calculate energy vs channel linear or quadratic
21. d as careful use of type specific standards but was incorporated into the probe software because standards that are similar to the planetary regolith may not be available especially if the subsurface regolith composition is unknown Further work on the fundamental parameters analysis algorithm should improve the calibration performance For the best results appropriate standards with certified compositions can be used with an empirical correction algorithm Measured 9 m N U O 9 o 4 6 8 10 Given 90 e N Figure 20 Measured vs given composition for a wide range of elements in all five standard reference materials 51 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Conclusions A borehole X ray fluorescence spectrometer XRFS has been successfully constructed and tested Miniaturization has been performed to a diameter of 27 1 mm and components can be configured in a variety of XRFS instrument designs Modifications can be easily incorporated such as an SDD detector the use of a different target X ray tube or use of radioactive sources for excitation Performance is very good with detection limits of about 10 ppm for many elements and detection of light elements down to magnesium at 1 496 Power consumption is 12 watts during data collection and the total energy per spectrum is comparable to previous planetary inorganic analysis instruments Adequa
22. d ep rite Ub de dads mee 1 VCE LOW AE 1 Borehole XRFS Software Installation essere 12 Insttunietit PICS OI ESS 15 Eypica HOST AUTOR unos te te edv cem Ea 19 Determining the Minimum Detection Limit 1121 40 Hardware Descrip erect ec eroe o a e 23 XRP Ire Ea CE oo eo E NAR ed aus goes oe eae eat 23 baden 26 Software DescrptIOnR sae eI a ER UU V RA REOS Ua cavae 29 X ray Tube Control DC a dota e dnte 20 Detector Data Acquisition 3l Save and Load Parameters DAR oce tI ide te d aues Ubros 33 Save and Load Spectrum SSF 34 Spectrum Processing 9B cece geen et ED Mq iie 36 Spectrum Display CSI o eastern t tr xen ue helen vaca edi s Ima seh ERR IRA 36 Instrument Performance Report eer eec i epe ee E CON e M RES 38 39 Test Plam 41 sa Od dde ss 42 COGI S TOES 3o oo decepta 52 Appendices 53 iii TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY TR 0703 iv U
23. d for out to 5 mm Beyond 10 mm the spectrum is no longer a reliable measurement of the sample 49 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY 0 03 0 02 7 0 01 0 01 0 02 A 0 03 N 0 04 0 05 Fraction Change in Total Counts 0 06 0 07 0 1 2 3 4 5 6 Day Figure 19 Variation in total spectrum counts over one week Point on Day 2 is after instrument was in continuous operation for 4 hr Results of the measurement stability test are given in Figure 19 Stability is about 296 except for the final point It is now known why this point is an outlier The two points on day 1 were taken when the instrument was first powered on and after several hours of operation The calibration linearity was checked by plotting the composition measured by the instrument against the certified composition for all elements in all of the SRMs below 10 weight percent Figure 20 Except for two outliers and several false positives the points above the line near zero composition the calibration is very good The analysis algorithm used here is a standardless algorithm that relies entirely on the fundamental TR 0703 50 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY parameters method to obtain the weight percent from the intensities in the spectrum No standards were used in calculating these results This is an advanced method that is not as goo
24. data 21 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY acquisition parameters such at X ray tube voltage and current are automatically stored with the spectrum The spectrum is stored in a file along with the information about the parameters under which it was acquired and enough of a description of the instrument to allow later analysis if necessary The file format used is the standard format for energy dispersive spectra adopted by the Microscopy Society of America and the European Microscopy Society Additional keywords were added to provide a complete description of the measurement conditions including instrument configuration see Table 1 European Microscopy Society standard format Version 1 0 see files emmff doc and emmff src at http www amc anl gov ANLSoftwareLibrary 02 MMSLib XEDS EMMFF There is a proposed format based on XML that is not yet standard See file EMSA MAS V2 XML 8 2002 pdf TR 0703 22 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Hardware Description XRF Interface Unit Low voltage power supplies COTS 15 VDC for op amps 15 VDC 1 5 amp for HV module 5 VDC for interlocks and detector Detector requires 0 5 A steady state with 1 A startup surge lasting 30 60 sec DAQ and control board COTS OnTrak ADR2000A USB to serial adaptor COTS Targus PA088 USB hub COTS D Link Model DUB H4 high speed USB 2 0 4 port hub Safety i
25. e X ray tube Operation Compares the emission current signal from the HV module to an on board set point If the emission current exceeds the set point for more than 5 sec turn off the X rays Detector power board COTS AmpTek PC4 3 Detector pulse processor board COTS AmpTek DP4 The detector system is completely isolated as well as electrically and magnetically shielded from the X ray tube power supply with one common ground point at the 5 volt power supply The signals from the X ray detector at the preamp output are pulses of about 10 microseconds duration and about 1 mV amplitude Their amplitude must be measured to within a few percent to obtain a useable X ray spectrum Electronic noise is the major limitation and is minimized Magnetic shielding is accomplished with co netic foil TR 0703 28 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Software Description X ray Tube Control XTC Description This module has two main purposes to display and allow the user to change the parameters related to the X ray tube and to control the high voltage power supply HVPS for the X ray tube The controls for this module are located on the main screen in the upper right corner of the interface Figure 4 The main parameters for the X ray tube are the high voltage kV and the beam emission current uA Typical values 35 kV and 2 uA The user must also input a complete description of the X ray tube f
26. e basic soil elements and extra elements in the form of contaminants Concentrations ranged from tens of percents for the basic soil components to below one part per million This provided a wide range to evaluate the instrument Samples were received from the National Institute of Standards and Technology as fine powders The samples were poured into specimen cups as received and presented to the instrument without further preparation Mars environmental conditions were simulated on a laboratory bench top using a glove bag Eight millibar carbon dioxide partial pressure was chosen as representative of the Mars atmosphere A gas mix of three volume percent carbon dioxide with helium making up the balance at Earth ambient pressure and gravity provided the same carbon dioxide density typical of Mars atmosphere measurements were made in this atmosphere 39 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Determining the Minimum Detection Limit MDL A spectrum is collected of a known sample containing the element for which the MDL is desired It is best to use a sample with a known element concentration less than 100 times the MDL The largest peak from the element is found usually or L a and the background is determined by a linear fit to the spectrum on either side ofthe peak To determine the total background counts the number of channels under the peak is multiplied by the average counts in the channels on eit
27. e to keep the entire spectrum in view e lt cursor Moves the cursor one channel to the left e cursor gt Moves the cursor one channel to the right e X zoom in Adjusts the X scale so that it displays a smaller range of X values centered around the cursor e X zoom out Adjusts the X scale so that it displays a larger range of X values centered around the cursor e X shift left Moves the view to the left approximately half of the plot range so that the user is looking at slightly lower energies X shift right Moves the view to the right approximately half of the plot range so that the user is looking at slightly higher energies e Y zoom Adjusts the Y scale so that it displays a smaller range of Y values Y zoom out Adjusts the Y scale so that it displays a larger range of Y values Analyze Click this button after calibrating to run an automated analysis of the sample It will return a list of elements present their concentrations and uncertainty Save spectrum Allows the user to save the current spectrum and some configuration information to a file on the computer These files are accessible by the load button in the Borehole XRF software and can also be opened in a word processing program or text editor 7 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Exit Exits the spectrum collection program The program will not prompt the u
28. ed Unclassified SAR NSN 7540 01 280 5500 Standard Form 298 Rev 2 89 Prescribed by ANSI Std 239 18 299 01
29. eracts mainly with the data acquisition board used to control the X ray tube high voltage supply and with the digital pulse processor board for the detector These functions are described more fully beginning on page 26 Typical Operation A typical X ray spectrum of terrestrial soil is shown in Figure 11 There are three significant features First are the large peaks in the spectrum between 3 and about 15 keV These peaks are from the elements in the sample and are the main features of interest Second are the peaks between 15 and 20 keV These are the characteristic peaks from the X ray tube anode material silver in this case that have been scattered toward the detector by the sample They can provide additional information but are not as straightforward to interpret The third feature is the background under the peaks The background is small in an XRF spectrum from a good spectrometer allowing detection of even very small peaks from elements at very low concentrations the minimum detection limit However it must be modeled and removed by the analysis algorithms to provide accurate measurements of the peak intensities 19 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY 100 000 10 000 X ray Counts 100 0 5 10 15 20 25 30 Energy keV Figure 11 Fluorescence spectrum taken with the borehole XRFS The soil sample was JSC1A Lunar Simulant Typical operation of the spectrometer by a user involve
30. eration Applies a voltage through a pair of resistors to the X ray tube anode over the umbilical cable One resistor is in the power supply and one is in the XRF Head Unit near the X ray tube anode This will produce a known voltage if the X ray tube is properly grounded If the umbilical cable lead is shorted then the voltage will be zero Provides a signal if the correct voltage is present and disable the X rays if not XRF Control Unit High voltage power supply board HV module COTS Filament driver and regulator APL UW Purpose Provides AC drive voltage for filament isolation transformer to heat filament Regulates filament voltage to achieve emission current set point TR 0703 26 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Background The electron beam in an X ray tube is generated from a hot filament at high negative voltage The electrons emitted from the hot filament are accelerated by the high voltage and strike a metal anode at ground potential The metal anode emits X rays The filament is heated by a current passing through the filament wire Since the filament is at high negative potential the heater current must be isolated by a filament transformer operating at 6 kHz electron beam current is regulated by the temperature of the filament which is controlled by the filament heater current Operation 6 kHz AC is generated by an oscillator whose output voltage is controlled by a feedback
31. fore they travel over the connecting cable The X ray Head is as small as possible to go down the smallest pre drilled hole and measure the composition of the regolith at various depths The 15 ft umbilical cable is permanently attached to the Head Unit it connects the Head and Control units The XRF Control Unit contains all of the essential electronics to operate the X ray tube and detector It constitutes the electronics that would be required for a future spacecraft instrument For the X ray tube there is the high voltage power supply HVPS the filament driver and regulator isolation amplifiers to provide monitor signals for the voltage and current and an over current protection circuit For the detector the unit contains a power supply board and the digital pulse processor board The XRF Interface Unit contains the hardware necessary to adjust and monitor the X ray tube voltage and current from the host computer several interlock sensors for personnel safety and the low voltage power supplies for the electronics This unit contains all of the support equipment that is necessary to operate the spectrometer on the ground There are several cables connecting the XRF Interface and XRF Control units The XRF Interface Unit also connects to the host computer via USB to the personnel safety outerlocks and to the main power line TR 0703 18 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY The software described here int
32. he allotted time has elapsed Note that this refers to accumulation time not live time Input Spectrum functions Start Click this button to begin taking a spectrum Stop Click this button to stop spectrum collection before the preset time has elapsed Clear This button clears the spectrum currently plotted Calibrate The user may calibrate the energy of the spectrum any time before during or after collection It is also possible to load and calibrate a previously saved spectrum Click Calibrate to open the calibration window enter the desired channel energy pairs in keV in the form channel energy click Compute Calibrate and Close It is also possible to type a desired energy per channel value and energy start value manually and then click Calibrate without pressing Compute The user may clear a previous calibration and return to the original channel values by pressing Remove calibration TR 0703 6 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Load This button allows the user to bring up a previously saved spectrum It is possible to enter a new spectrum label and operator zoom in out calibrate analyze and re save any previously saved spectrum Plot controls Note none of these buttons affect data collection Restore Restores the spectrum plot to its original scale and causes it to begin automatically adjusting the Y scal
33. heir arrival times In a given time interval the number of X rays that are detected has an intrinsic variance the square of the standard deviation equal to the number of X rays This means that the relative standard deviation 1s one over the square root of the number For a given geometry and sample composition the number of X rays detected from a particular element is proportional to the source strength and the measurement time Detecting an element depends on both the number of X rays collected from that element and the background present even in the absence of that element Because the background is also subject to the same variations the MDL is usually taken as three times the TR 0703 38 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY standard deviation of the background converted to elemental concentration by an appropriate calibration coefficient This is equal to three times the square root of the background counts in the spectrum Both the desired signal and the background are proportional to the source strength The background arises from scatter of the continuum from an X ray tube and the detector peak to background ratio Materials and Methods Standard Reference Materials Standard Reference Materials SRMs numbered 2709 2710 2711 97B and 2702 from the National Institute of Standards and Technology were used for the characterization tests These SRMs are a set of selected soils with varying amounts of th
34. her side of the peak The gross peak counts are similarly determined by summing the counts in all channels under the peak The net counts from the element are the gross counts in the peak minus the total background counts Next the square root of the total background counts is multiplied by three then multiplied by the ratio of the known element concentration to the net counts from the element This yields the MDL in the same units as the known concentration Note that this procedure assumes a linear relationship between net counts and concentration which is a good assumption at low concentrations near the MDL MDLs given in this instrument performance report were calculated using this procedure TR 0703 40 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY 120000 100000 80000 97B o 2702 D E 2711 x 0 5 10 15 20 25 30 Energy keV Figure 13 Raw spectra of five SRMs acquired with the borehole XRFS Test Plan Summary Determine the MDL for the elements Mg Zr Cd and Pb Measure power consumption during spectrum collection Dry water saturated and frozen sample Variation with distance to probe in case borehole diameter is not constant Measurement stability vs time Calibration linearity 41 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Results Figure 14 shows typical spectra from the borehole instrument The specimen was a terrestrial soil SRM 2709
35. me sec Fast Count 1144643 Accum Time 100 000 sec O Live Time 71 969 sec Input spectrum Spectrum analysis cu asks Real tim File FRONS RT mE Start Load Spectrum with background and fit unkQuant Results Stop Elem X Err Int Clear 1 51 9205 2 3543 Rb 0 1577 4 3147 2 Calibra K 8 3675 1 16354 biot te Cd 0 3543 7 1809 Da Ca 11 5213 1 29568 Sn 0 6938 6 2110 us Ti 31 3978 2 6602 n n Fe 19 1297 1 209024 UE estore Eu 1 0360 3 6000 lt cursor cursor gt Tb 2 7611 2 18367 v D Scand 0 0435 17 548 0 in out X shitt X shitt Cursor igh Energy Y zoom Y zoom keV 5 Save 5 counts 396 Spectrum Exit Figure 12 Borehole XRF interface indicating interlock failure In Functions Set and display X ray tube voltage kV Set and display X ray tube emission current uA Check limits for X ray tube parameters Check and display status of safety interlocks X ray on off Warning light and fail safe Electrical interlock e Filament connector engaged e Over current signal e Ground failure detect Turn X rays on and off TR 0703 30 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Ramp up X ray tube gradually to full operation Bring up kV to no more than 10 kV Bring up emission current to no more than 5 uA Raise kV and uA gradually together to specified values Communicate with HVPS e USB port or other communication parameters Commands to ADC and DAC e ADC and DAC con
36. mits for a number of elements in parts per million are presented in Table 2 They are computed using the three sigma method and assuming a linear relationship between net counts and the certified concentration The background was linearly interpolated from the counts on either side of the peak Detection limits for each SRM Reider Gellert J Br ckner Klingelh lfer Driebus A Yen and S W Squyres J Geophys Res 2003 108 8066 8078 DOI 10 1029 2003JE002150 43 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY are given along with the average values SRM 2710 has rather high concentrations of many of the elements so the linear concentration relationship may not hold This causes the detection limits to be larger in this material They were included in the averages since they have the effect of raising the detection limits and including them avoids any bias toward lower values None of the SRMs contained Mg at a level that gave an unambiguous peak A compound with magnesium as a major element was used to determine the magnesium detection limit Talc or magnesium silicate hydroxide is a readily available magnesium compound as baby powder obtained from a local pharmacy and was used for this purpose Lowering the X ray tube voltage to 20 kV decreased the magnesium detection limit from about 3 to the 1 4 value Table 2 The ability to change the excitation conditions is another strong
37. nterlocks and control APL UW X ray on off Purpose Turns the X ray tube on and off including ramping filament up and down and safety disabling the high voltage module Background This signal controls the main functions of the X ray tube power supply system It is disabled whenever one of the safety signals see below is absent It will shut down and latch in the off condition whenever one of the safety signals disappears Operation Logic circuit responds to a binary signal from the DAQ tests all of the safety condition signals and provides signals for HV disable filament voltage ramp control and status to the DAQ board 23 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Warning light and fail safe Purpose Controls the warning light 115 V AC external lamp turning it on and off with the X rays Provides a safety signal that indicates when the lamp is working Background One of the federal safety requirements for X ray systems is a warning light that turns on whenever the X ray producing system is energized defined as high voltage on The light must be fail safe in that the X rays will not come on if the light bulb is burned out Operation Solid state relay to turn the power to the external socket on and off A current detector full wave bridge rectifier in parallel with Zener diodes driving a 5 V DC relay indicates that the external lamp is drawing current 1 e connected and not
38. ocessor separates this pulse from the noise determines its amplitude digitizes the amplitude and counts the pulses with matching amplitudes to collect a spectrum The silicon diode is taken to about 60 C by Peletier cooling to reduce the noise and allow better resolution of the pulse amplitude The energy resolution in the spectrum is limited by the electronic noise in the diode and is typically about 150 electron volts The digital pulse processor is optimized for detecting and discriminating X ray pulses from this diode from the background noise The count rate the maximum rate that X rays can strike the detector is limited to about 10 000 per second by the speed of the pulse processing The count rate is determined by the material being measured and the strength of the X ray source The rate is typically adjusted by controlling the beam current in the X ray tube as described above 17 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Hardware physical units The subsystems are packaged into three units the XRF Head that goes down the borehole and makes contact with the material being measured the XRF Control Unit and the XRF Interface Unit The X ray Head contains the X ray tube and the silicon diode X ray detector It also has a filament isolation transformer for the X ray tube to isolate the filament heating power from the high voltage It contains a preamplifier for the detector to amplify the pulses be
39. or proper operation of the quantitative analysis software These parameters are in a separate dialog that appears on request but is usually invisible Figure 8 The HVPS has a series of safety interlocks to prevent accidental exposure of personnel to high electrical voltages and X ray radiation The status of these interlocks is clearly visible to the user and turn red if any fail Figure 12 Control of the HVPS requires turning the X ray on and off under user control and responding to any changes in the interlock status by turning off the X rays The X ray tube voltage and current settings are converted from the display units KV and uA to the DAC integer values and sent to the DAC using its commands The actual values are read from the DAC and converted to the display units When the X rays are turned on the X ray tube must be ramped up to the operating conditions gradually see ramp up under functions 29 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Borehole XRF APL UW load params 1029 DP4 X ray control panel piis X rays P 5 Press Off Test spectrum SRM 2711 to Reset no micro controller failure active lamp connect Setting Actual cone lamp Tim Elam no over current Dperator set KV 0 0 head gnd fault Acquisition set u 0 0 Ext interlock SW failure change es Extinterlock SW connect Preset Ext interlock SW status Ti
40. read in by the software and displayed and analyzed just as newly collected data are handled All of the information necessary to display the spectrum and to allow later re analysis if desired is stored in the spectrum file Functions Set and display spectrum file name Save data and all relevant parameters to file Load data and all relevant parameters from file File format The file format is the standard format for energy dispersive spectra adopted by the Microscopy Society of America and the European Microscopy Society Additional 2 European Microscopy Society standard format Version 1 0 see files emmff doc and emmff src at http www amc anl gov ANLSoftwareLibrary 02 MMSLib XEDS EMMFF There is a proposed format based on XML that is not yet standard See file EMSA MAS V2 XML 8 2002 pdf TR 0703 34 keywords Table 1 were added to this format to allow inclusion of the instrument UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY parameters used to analyze the spectrum Table 1 Keywords for XRFS spectrum output and parameter files added to the standard format for energy dispersive spectra Keyword Description Default value kVsetting X ray tube kiloVolts Setting 20 00000000 uAsetting X ray tube microAmps Setting 5 00000000 kVscaleln kV Input Scale 9 56999969 kVoffsetln kV Input Offset 0 00000000 uAscaleln u
41. s these steps When power is turned on the X ray source is off not producing X rays and the detector starts to cool down The user places a specimen in front of the measurement window on the side of the head or places the head in a borehole The user then closes a radiation safety enclosure When the safety enclosure is closed a safety interlock switch closes allowing the X rays to be turned on The voltage and current for the X ray tube are set at this time or previous settings are read in and used The user chooses a data acquisition time clears the spectrum in the digital pulse processor DPP and starts data acquisition The spectrum is displayed as it is collected and the user will typically check the total count rate and make sure the spectrum looks correct perhaps examining some regions more closely using zoom and pan The user may be looking for particular elements and will thus focus on the chosen elements The TR 0703 20 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY user will then stop the data acquisition change any data acquisition parameters to optimize the spectrum clear the spectrum and collect the desired data The data are displayed as a function of the X ray energy To do this the detector pulse height must be calibrated to match the X ray energies This is typically done using X ray peaks from known elements The calibration must be checked typically daily and may need to be repea
42. s used have only a contact for the negative high voltage not for the positive return path ground in this case The ground return path is via the filament connector If the high voltage is energized with the high voltage connector in place and the filament connector dangling then a shock hazard condition can be produced Operation A simple logic circuit that passes through the external filament connector via two extra pins Over current signal Purpose See over current cutoff under high voltage power supply board in the XRF Control Unit above This signal is passed through to the DAQ and should remain after the X rays are turned off until reset via the DAQ usually by the X rays off signal Background This is just an interface to the over current cutoff from the high voltage power supply board 25 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Operation Logic circuit that is part of the X ray on circuit Ground failure detect Purpose Insures that a safe return path for the high voltage exists and avoids potential shock hazards Background If high voltage is applied to the X ray tube and a connection between the X ray tube anode and the return current path to the power supply ground fails then a potential shock hazard exists This circuit tests the ground return path by applying a voltage to the X ray tube anode via a resistor then testing to be sure that voltage is shorted to ground Op
43. ser to save the current spectrum so it is necessary to save if desired before exiting Borehole XRF APL UW X ray control load ar xrays OFF ON Acq Date Acq Time Press Off Lebel to Reset no micro controller failure yes active lamp connect Setting Actual ok qm lamp 5 Operat no over current gatis setKV 0 0 no XRF head gnd fault Acquisition set uA 1 01 no Extinterlock SW failure change E yes Extinterlock SW connect Preset closed Extinterlock SW status Time sec Fast Counts 0 Accum Time 000 sec Live Time Input spectrum Spectrum analysis Slow Count 0 8 Real tim File Analyze Load Ss Results 1 80 c 70 o 60 u 50 n restore 0 ze 20 lt gt 1 X zoom X zoom 8 in out 0 500 1000 1500 2000 aeg UM Channel one Save 1 ios arco piscem counts 0 Spectrum Exit Figure 4 Main screen view upon starting the program BoreholeXRF TR 0703 8 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Borehole XRF APL UW load 0 4 X ray control load params conf 9 X rays panel panel y CON OFF ON Acq 141 AM Date 97 900 Spectres Press Off Label to Reset no micro controller failure yes active lamp connect Setting Actual ok See lamp Tim Elam no over current Operator set 5 351 no XRF head gnd fault Acquisition set uA Yi 19 no Extinterlock SW fail
44. te data can be collected in 100 sec facilitating investigation of strata with vertical resolution of about 1 cm in a reasonable time TR 0703 52 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Appendices appendices are available on the CD R that accompanies this report Appendix A Digital Pulse Processor User s Guide and Operating Instructions Appendix B X ray Tube Product Documentation Appendix C Detector specification sheet Appendix D Borehole XRFS wiring diagrams Appendix E Borehole XRFS safety interlock control board schematic Appendix F Borehole XRFS HVPS power and control board schematic Appendix G Borehole XRFS head unit and umbilical cable schematics Appendix H Borehole XRFS safety interlock control board layout Appendix Borehole XRFS HVPS power and control board layout Appendix J Bill of materials for safety interlock control Appendix K Bill of materials for HVPS power and control board Appendix L Borehole XRFS detector interface board schematic Appendix M Borehole XRFS detector interface board layout Appendix N Borehole XRFS safety controller software program by Peter Sabin 53 TR 0703 REPORT DOCUMENTATION PAGE Public reporting burden for this collection of information is estimated to average 1 hour per response including the time for reviewing instructions searching existing data sources gathering and maintaining the data needed and reviewing the collection of information
45. ted click Finish e Install Shield Wizard for TracerDAQ click Next Destination Folder click Next e Ready to Install click Install e Completed click Finish e User s Guides Setup select USB then click Install Driver is installed This takes a few seconds e MCC DAQ message box You must restart your system click Yes After system has restarted connect Borehole XRF hardware to USB port and turn power on Found New Hardware Wizard should appear Can Windows connect to Windows Update choose not at this time click Next Install software for DP4 Digital Pulse Processor see also page 19 of Appendix A Select Install from a list or specific location click Next Select Don t search I will choose the driver to install click Next Hardware type Select Human Interface Devices click Next Select the device driver Click Have disk Insert the AmpTek CD into the CD drive Click Browse Install From Disk file dialog appears Navigate in the file dialog to My Computer AMPTEK USB Driver Win2k XP apausb2k ini Click Open e Back at the Install From Disk dialog click OK e Back to Select the device driver dialog click Next Driver is installed This takes a few seconds 13 TR 0703 UNIVERSITY OF
46. ted at irregular intervals Once data are collected they can be stored in a file and or analyzed further Further analysis consists of modeling the background finding any peaks in the spectrum and associating them with the corresponding elements determining the net intensity of the peaks and converting this net intensity into weight fractions of the elements The background and a reconstruction of the spectrum using the extracted net intensities are displayed This allows the user to quickly and visually evaluate the analysis of the spectrum The element list and weight fraction of each element together with estimated uncertainties are also displayed The conversion from peak intensity to weight fraction is accomplished using a physical model of the interaction of X rays with the material being analyzed This model requires a complete description of the instrument to give accurate results This description is more information than is typically changed by the user such as fixed angles and distances within the components It is also more information than the software needs to control the instrument This information is read in from a parameter file and is usually not changed It can be initially entered and changed via second level dialogs that are invisible unless needed The user can also enter information about the material being analyzed and can change the instrument description information to be stored with the spectrum if desired The
47. ure Acquiring change nn yes Extinterlock SW connect Preset closed Extinterlock SW status Fast Count 588847 Accum Time 51 651 sec Live Times 37 274 sec Input spectrum Spectrum analysis Real tim File Analyze Load Results 24 2 RAG MA 0 6 restore 0 4 lt cursor cursor gt 0 2 X zoom zoom 0 0L in out 500 1000 1500 2000 X shitt X shit Cursor Channel Y zoom Y zoom ch 1024 Save 4 counts 1 Spectrum Exit Figure 5 View of laptop display during spectrum acquisition Calibrate Enter channel ke pairs in the box below EnergyStarl 1566 4 i 0 531 22 166 EnergyPerChannel Calibrate Calibration ius Figure 6 View of calibration control window 9 TR 0703 Borehole XRF APL UW load params re j ta mE panel panel OFF ON Acq Date 9070057 Press Off to Reset Spectrum Test spectrum SRM 2711 Label Setting Actual Operator Tim Elam setKV jb 35 1 Acquisition set uA 1 9 Preset 100 0 Accum Time 100 000 sec Live Time 71 969 sec Fast Count 1144643 Slow Count 823788 Input spectrum Real tim File taj Spectrum with background and fit unkQuant UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY no micro controller failure yes active lamp connect ok active lamp no HVPS over current no XRF head gnd fault no Extinterlock SW failure
48. v N E s m m 5 E amp x 5 3 co 529 E o 5 5 3 2 H 8 8 8 2 2 8 3 8 5 k s x E 3 5 Pc 558 2 gt 5 E 5 2 3 3 3 20 938 sma 252m 5 528 5 5 al A 5 5 x 5 3 gt gt N 6 Pe 2 4 0 gt lt 2 o 8 88 pum 8 8 2 x Figure 3 Connection diagrams for Interface Control and Head units of the XRF spectrometer TR 0703 4 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY Spectrum collection l 2 3 4 5 6 1 10 11 Place the sample to be analyzed before the probe window Close the radiation safety enclosure and be sure the interlock switch is closed Start the program BoreholeXRF the main screen appears Figure 4 Turn on the high voltage to 35 kV and the emission current to 2 pA Set the preset time to the desired interval Click Start The actual kV and uA values should be near the setting values they may take one or two minutes to reach these values because of the slow ramp Acquiring will appear in red on the screen Figure 5 A spectrum will begin to appear in the plot box in the lower left corner of the interface Figure 5 To calibrate click Calibrate and enter points in the form channel number energy in keV in the window that opens Figure 6 Then click Compute then Calibrate then Close You may calibrate
49. ver anode X ray tube Comet NA Stamford CT see Appendix B The energy dispersive X ray detector is 7 mm Si PIN diode Amptek Inc Bedford MA see Appendix C This detector was chosen mainly because of the availability of a preamplifier compatible with the size restrictions It has a good peak to background ratio and a 12 micron thick beryllium window for light element sensitivity A digital pulse processor from the detector manufacturer Amptek Inc Bedford MA converts the detector output to an energy spectrum see Appendix C The energy calibration is linear and determined from the location of the iron characteristic emission and silver elastic scatter peaks Because the borehole diameter cannot be controlled with precision the collimation and beam definition geometry are optimized to allow for varying distance to the measurement volume at the borehole wall The excitation beam is larger than the area viewed by the detector making the signal less sensitive to the wall distance The performance requirement is to detect the elements magnesium through zirconium atomic numbers 12 through 40 in the periodic table and the elements cadmium through 15 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY lead atomic numbers 48 through 82 in the periodic table Figure 10 Engineering drawing of the final design of the downhole assembly The enlarged area shows the X ray tube and the detector Major hardware subs
50. version constants Set and display X ray tube and instrument description e X ray tube type side or end window e Anode material e Be window thickness Electron incident angle Takeoff angle e Aperture size and distance Filter material and thickness if any e Path length from X ray tube to specimen Angle that X rays from tube strike specimen incidence angle Detector Data Acquisition DET Description The X ray detector acquires the spectrum its associated electronics are commercial off the shelf The manufacturer Amptek Inc Bedford MA also supplies a library of communications and control routines that operate over a USB interface The main function of the DET module is to drive these functions to acquire the spectrum once the X ray tube is operating and the user requests data be collected As with the X ray tube 31 TR 0703 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY there are several data acquisition parameters that the user can change Some of these appear on the main screen and some in a separate dialog Figure 9 The signal from the X ray detector is analyzed by a digital pulse processor DPP that is specialized for energy dispersive X ray detector pulses Many of the parameters for this DPP are software changeable but require specialized commands and some tuning procedures The parameters are loaded at startup from a database One of the auxiliary functions of the detector data a
51. ystems The X ray source is a miniature but otherwise conventional X ray tube It generates X rays by bombarding a metal anode with high energy electrons The electrons are TR 0703 16 UNIVERSITY OF WASHINGTON APPLIED PHYSICS LABORATORY produced in a hot filament and accelerated to high energy by a high voltage The filament heater power controls the beam or emission current The X ray output is proportional to this current The electron beam energy is controlled by the high voltage applied to the X ray tube This voltage determines the X ray spectrum emitted by the tube and is one of the main parameters used to control the spectrometer The X ray tube has a very high vacuum inside and the X rays exit via a thin window Other parameters that influence the X ray spectrum of the tube are the angles that the electron beam makes with the anode and the exit window the material and thickness of the exit window and of course the anode material The X ray detector is based on a silicon diode that is reverse biased to provide a thick region of high resistivity silicon with an electric field across it The X rays are absorbed in this region and produce electron hole pairs in the silicon The high electric field separates the electron hole pairs and produces a pulse of charge at the electrodes of the diode This pulse is amplified and its amplitude measured Its amplitude is proportional to the energy of the absorbed X ray A digital pulse pr
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