• Getting Help for the DGF
Contents
1. There are two DACs per channel One controls the gain of the analog amplifier stage preceding the waveform digitizing ADC The other controls the DC offset that is subtracted from the input signal to bring it into the ADC range Note that the ADCs are dc coupled to the DGF 4C inputs and thus compensation for any DC offset is necessary You will rarely have to set this manually as the DC offsets can be adjusted automatically through clicking on Adjust Offsets on the Oscilloscope The DAC settings are given in units of V V and V respectively The voltage gain computed is the ratio between the pulse height at the module input to the pulse height at the ADC input Note that the ADC has a 1V input range which is mapped onto integers from 0 to 16k Histogram Control This section shows the parameters controlling the operation of the multichannel analyzer built into the DSP memory Energy values are reported as 16 bit fixed point numbers In Revision C modules the scaling is such that the LSB corresponds to 1 16th of an ADC step 12bit ADC The MCA memory is limited to 8192 words It can all be used for one channel or be shared equally among 2 or 4 channels If you want to map the full energy range into the available MCA memory you have to combine bins at least 243 8 bins for a single channel spectrum One bin means 1 LSB of the energy word In Revision D modules the scaling is such that the LSB corresponds to 1 16th of an ADC step 12bit AD2. are computed to 16 bits precision i e correspond to 64k spectra As the memory allows for only 32k words per channel for Revision C modules 8192 words total for all channels bins have to be combined according to the Binning factor for each channel You can select the module you want to inspect and you can add or remove individual channel displays by clicking the MCA check boxes For energy spectra you can make Gaussian fits to peaks in the histograms On a channel by channel basis you can set fit ranges The GaussFit button calls the fitting routine The routine does take a constant background term into account though its value is not displayed The fit results that are displayed include the peak position the number of counts in the peak and its relative and absolute full width at half maximum FWHM calculated from the Gaussian fit For best results be sure to extend the fit range to cover some of the constant background To calibrate your energy scale you can after the fit type the true energy value into the field Peak and DGF 4C Online Help 11 the scale will automatically be adjusted The Sum Histo button computes the number of histogram entries between the limits set in the min and max fields minus background The result is displayed in the area field The Save and Read buttons allow to store individual spectra and read back stored spectra from disk List Mode Traces After a list mode run has finished the pulse sh
3. signal arrival time using the digital equivalent of a constant fraction discriminator For this to work correctly the rising part of the signal should be fully contained in the recorded trace The time computed is the arrival time after the start of the acquired waveform in units of 1 256th of an ADC sampling interval This information can be used to replace the recorded channel time which is derived from a digital leading edge discriminator cf the User s Manual The DSP code shipped with the DGF 4C has some pulse shape analysis capabilities already built in One of these functions the digital constant fraction discriminator takes an input parameter the threshold percentage The default value is 25 since it is a commonly used threshold fraction for this type of discriminator The result of the computation is the time of signal arrival measured with respect to the start of the acquired waveform The result is written into the channel header in the linear output data buffer cf the User s Manual for details Bit 11 Enable contribution to multiplicity You can switch on any channel s ability to contribute to the multiplicity output with this bit It also comes with a programmable width set by the variable Pulse width The pulse width is given in sampling clock periods of 25ns HitEditPanel Settings gt Coinc Pattern Edit The coincidence pattern mask is useful for DGF 4C channels operating independently from each other though they m
4. the flat top plus the signal arrival may jitter by up to one decimated clock cycle with respect to the decimated clock You should therefore make the flat top two notches longer than the signal rise time The sum of energy filter rise time and flat top cannot exceed 31 decimated clock periods If you type in a rise time or flat top value that violates this bound the DGF 4C Viewer will adjust it accordingly The trigger threshold can be set in units of ADC steps You can get an idea of what the noise in your system is by looking at the trace acquired in the Oscilloscope located on the Calibrate Tab Use the mouse to zoom in on parts of the displayed trace s and estimate the noise Pulse Shape Analysis The trace length and delay values to be entered here both in units of us govern the waveform acquisition Especially if you request pulse shape analysis these two parameters have to be set correctly You can use the delay parameter to move the trace Delay measures the trigger time with respect to the beginning of the recorded trace For ordinary data taking the trace lengths are up to 25 600us for each channel If less than four channels are marked as good channels the trace length could be longer than 25 600us for the good channels The waveforms will be read in 25ns increments from FIFO memory The PSA Start and PSA End specify the trace range for Pulse Shape Analysis PSA Currently DGF 4C supports two types of PSA XIA_PSA and USER_PSA XI
5. A_PSA reports the signal arrival time by measuring the time when the trace reaches a preset percentage level of its magnitude The preset percentage threshold is defined in the DSP parameter CFDTHR The arrival time is relative to the starting time of the trace So for XIA_PSA the PSA Start and PSA End should be set to include the rising edge of the trace USER_PSA is a user defined PSA value Action Buttons DGF 4C Online Help 4 Edit Module CSRA MCSRAEditPanel Edit Channel CSRA CCSRAEditPanel Edit Coincidence Pattern HitEditPanel Copy Copy settings CopyPanel Extract Extract settings ExtractPanel Files Path Files and path AllFilesPanel Load Load settings Save Save settings MCSRAEditPanel Settings gt Module CSRA Edit In the Module control status register MCSRA options are set that affect the module as a whole The option Write to Level 1 buffer is the Bit O of MCSRA It is unused in the current software revision but reserved for compatibility with earlier revisions It is used to specify the event processing buffer but now this control is incorporated in the run type number The options Set Switchbus 2 DSP Trigger Termination and Set Switchbus 5 Fast Trigger Termination are Bits 10 and 13 of MCSRA respectively They are used to provide termination for external triggers from the backplane bus connector Even pins on the connector should be connected to the corresponding odd pi
6. C Spectra are stored in the extended memory of 32768 words for each channel To see the full energy range you have to combine at least 2 1 2 bins Binning Factor 1 In Revision E modules the scaling is such that the LSB corresponds to 1 4th of an ADC step 14bit ADC Spectra are stored in the extended memory of 32768 words for each channel To see the full energy range you have to combine at least 2 1 2 bins Binning Factor 1 If you want to see a certain range of the spectrum at higher resolution you can enter a minimum energy in the line Cut Off Energy Emin and reduce the number of bins that have to be combined Decay Time The Decay Time is the exponential RC time constant of the preamplifier It is required in order to properly calculate corrections to measured energy values To set and measure the decay time enter an estimated value then click on the Find button You can also enter a known good value directly in the control The RC calibration needs to be performed only once for a given preamplifier The result is then stored in the parameter database and can be saved in the settings file by clicking on the Save DGF 4C Online Help 8 button in the Settings tab Oscilloscope Calibrate gt Oscilloscope The Oscilloscope shows 8192 untriggered ADC samples from the input for each channel The time between samples can be set using the dT variable The display is updated through its Refresh button The DC offset
7. DGF 4C Online Help 1 e Getting Help for the DGF 4C There are several ways to get help for the DGF 4C You can use IGOR s built in help browser to access the DGF 4C specific help file by selecting Help gt Help Topics from the top menu bar Choose DGF4C Help in the popup menu on the left and select the appropriate help topic from the list on the right Each DGF 4C Run Control Panel also has a Help button which directly displays the help topic for that panel In the help topics click on blue underlined links to jump to cross references e Getting Started Preparations 1 2 3 4 Install Wavemetrics IGOR Pro Install the DGF4C software from XIA see file readme txt on CD ROM Install the DGF 4C modules and CAMAC controller in the CAMAC crate Connect detector signals to the DGF 4C modules using the cables supplied by XIA Find DGF4C pxp in the installed folder and double click it to open the DGF 4C Viewer Initial Startup When the DGF 4C Viewer has been loaded the DGF 4C Start Up Panel should be prominently displayed in the middle of the desktop It will prompt you to do the following 1 Specify the DGF 4C modules First select the number of DGF 4C modules in the system Then specify the CAMAC slot number in which each module reside and the name of the FPGA configuration file to be used with each module By default the Viewer assigns every module the same FPGA configuration but you can edit it by entering diffe
8. al on the distributed DSP trigger line This allows for master slave operation as outlined in the User s Manual Bit 1 Measure individual live time This bit will in almost all applications be opposite to bit 0 Its setting decides who asserts the live time control When cleared the DSP ensures that during the event interrupt no channel can generate another trigger and latch new event data at least not after the coincidence time window see HitEditPanel below This setting is useful in master slave operation and almost in all cases where list mode data are required On the other hand when channels are operating independently and only MCA information is needed MCA mode but not list mode data then this bit should be set to achieve the highest throughput Bit 2 Good channel Only channels flagged as good will be read out This setting has no bearing on the channel s capability DGF 4C Online Help 5 to issue a trigger There can be a triggering channel whose data are discarded Bit 3 Read always Set this bit if you want a good channel to be read out even if it did not report a hit It cannot report valid energy or timing data in that case but if operated in group trigger mode you will get a valid waveform This way you can collect waveforms not biased by trigger requirements Bit 4 Enable trigger You can switch on any channel s ability to contribute to the event trigger with this bit Bit 5 Trigger positive For channels with trig
9. and extract settings Energy and Trigger Filter In this section you can set the rise and flat top times for the energy and trigger filter of each channel The units of time are us The energy filter uses averaging of the ADC data and then operates the same filter core at a decimated i e reduced clock rate As a result there is a granularity of 0 050us for 1 bit times 2 decimation 0 100us for 2 bit times 4 decimation 0 200us for 3 bit times 8 decimation 0 400us for 4 bit times 16 decimation 0 800us for 5 bit times 32 decimation and 1 600us for 6 bit times 64 decimation corresponding to one cycle of the decimated clock The DGF 4C Viewer knows which decimation has been loaded and adjusts the parameters you typed in accordingly The trigger filter is always operated at the ADC sampling rate Its rise time can be varied between 25ns and 775ns Its flat top however is valid between Ons and 750ns The trigger filter will most often use a flat top comparable with the average signal rise time In applications with very short rise times a flat top of zero will give the best pileup rejection performance Employing a trapezoidal filter avoids the kind of ballistic deficit that occurs when a finite rise time signal is used in conjunction with a Gaussian shaper The energy filter flat top time should thus be a little larger than the longest rise time expected The output of the energy filter is sampled one decimated clock cycle before the end of
10. ape can be displayed on an event by event basis in the List Mode Traces panel The most recently acquired data file will be searched for the event required in the Event number field The display will show the ADC traces from the selected module and the associated energy for those channels that reported a hit in this event Traces are scaled as 16 bit numbers but to match the ADC the associated energies are scaled as 12 bit numbers i e divided by 16 This is true even for Revision E modules with a 14 bit ADC In order to display traces from an earlier experimental run one needs to change the Data File name by entering it directly in the Data File control or clicking the Find button List Mode Spectrum Pulse height spectra can be reconstructed from list mode data stored on the disk The file shown in the Data File field will be processed and the resulting histograms will be displayed for the selected DGF 4C module Use Read after changing the data file to process the new data and Histo to update the displayed spectrum The full spectrum length is equal to 64k channels Use No of bins and Delta E settings to compress the spectrum such that it fits the display Hint use 8000 and 4 to see the full range of data and then adjust these numbers to zoom into the range of interest The number of bins and the deltaE variables are kept in memory for each channel individually Be sure to select the channel of interest prior to changing the
11. ay be sharing clocks and triggers With this mask you may require that an event as witnessed by an individual channel match any of the preset hit patterns to be accepted by the DSP An example shall illustrate this feature Assume a single module connected to 4 detectors which DGF 4C Online Help 6 observe a Na 22 source emitting back to back 511keV gamma rays from positron annihilation Channels 0 and 1 are connected to one pair of back to back detectors and channels 2 and 3 are connected to a second pair of back to back detectors You are interested only in gammas from positron annihilation Thus a coincidence in channel O and 1 or a coincidence in channel 2 and 3 is required If all 4 channels were in coincidence that would be fine too So the acceptable hit patterns would be 0 0 1 1 1 1 0 0 and 1 1 1 1 where the right most digit indicates channel O and the left most is for channel 3 To achieve the desired behavior you have to select the three acceptable hit patterns in the HitEditPanel by checking the appropriate boxes and deselect all other hit patterns by not checking their boxes In general with 4 channels there are 16 distinct possible hit patterns and you can select any combination of these to be a valid event If you want to disable this feature you should check all boxes in the HitEditPanel i e accept any hit pattern Coincidence Window A delay time set in the Pulse Shape Analysis section increases the overall event tim
12. e Consequently the width of the coincidence window in 25ns ticks has to be adjusted to accommodate the full event Usually this is done automatically by the DGF Viewer and there is no need to edit the HitEditPanel manually On the other hand if the delay time is decreased a smaller coincidence window is possible This would reduce data processing time and allow for a higher event rate However to avoid overwriting a large coincidence window intentionally set by the user the value is not adjusted automatically Instead the HitEditPanel displays both the minimum coincidence window and the actual coincidence window The user can set the actual coincidence window but it should not be smaller than the minimum coincidence window CopyPanel Settings gt Copy This panel can be used to copy parameter settings from one module to another The source module and channel are selected at the top of the panel The parameters to be copied are organized into list box in the left hand column The right hand column shows the destination channels and modules for the copy operation The Items to copy shown on the Copy Panel and the actual variables to be copied are listed below Items Actual variables to be copied Gain Gain V V Offset Offset V Sum SUMDAC Filter Energy Filter Rise Time and Flat Top Baseline Cut Trigger Trigger Filter Rise Time and Flat Top Trigger Threshold FIFO Trace Length Delay dT us PSA Start PSA End CFDTHR CSR Cha
13. gering enabled this causes triggering on the rising edge of the input signal when the bit is set and triggering on the falling edge when the bit is not set The core of the trigger filter FPGA can only trigger on a rising edge So if the bit is not set the FPGA will invert the signal before storing it in the FIFO and sending it to the core Bit 6 GFLT required In a larger experiment you may want to exercise control over which events to accept and which to reject in a way that takes into account multiplicity information from many modules and possibly signals from other devices as well The external logic may be fast enough to make a trigger decision within an energy filter rise time If so it should send out a pulse that is logic 1 NIM levels 1 0 8V during the time when the channel would latch data and generate a trigger which happens no earlier than one energy filter rise time and no later than rise time flat top 2 decimated clock cycles after event arrival When bit 6 is set the channel requires the presence of a global first level trigger GFLT to latch data and issue a trigger Bit 7 Histogram energies Switch on incrementing an energy histogram in the DSP s MCA memory with this bit You can choose to have histogramming in list mode runs The histograms will continue to be updated over multiple runs started with the resume run command Bit 10 Compute constant fraction time The DSP can use pulse shape analysis to compute a precise
14. is box unchecked if the CAMAC controller used for data read out cannot send an interrupt to the data acquisition host The Jorway 73A falls into that category Alternatively the host could poll for LAMs The IGOR talks to master controller option is used when the Jorway controller is the master controller in the CAMAC crate When checked the Viewer will broadcast certain commands to all DGF 4Cs in the system As of this writing this is a broadcast to all stations in the crate Thus this feature may be used only if there are no other modules besides the J73A and the DGF 4Cs in the crate After making the above selections click Start Up System If no error messages appear in the IGOR history window the system is initialized You will now see the main DGF 4C Control Panel from which all work is conducted The tabs in the Control Panel are arranged in logical order from left to right For most of the actions the DGF 4C Viewer interacts with one DGF 4C module at a time The number of that module is displayed at the top right corner of the Control Panel inside the Module control Next to the Module control is the Channel control which specifies the current channel the DGF 4C viewer is interacting with The Module and the Channel are the target for all actions executed from the Viewer Proceed with the steps below to configure your system 1 In the Calibrate tab click on the Oscilloscope button This opens a graph that show
15. lect other channels while working on only one channel You can do a Gauss fit on a peak by entering values in the Min and Max fields as the limits for a Gauss fit You can also use the mouse to drag the Cursor A and B in the MCA spectrum to the limits of the fit Make sure Cursor A and B are put on the same trace by looking at the left bottom corner of the MCA spectrum If not mouse click on the left bottom corner to select the trace Click Gauss Fit to perform the fit Enter the true energy value in the Peak field to calibrate the energy scale If you are not getting a nice looking spectrum you may need to adjust some settings such as filter rise time and flat top etc Refer to the User s Manual for details DGF 4C Control Panel The Main Control Panel is displayed on the desktop after starting the IGOR experiment file DGF4C pxp Using the four control tabs arranged in logical order from left to right you can set up the system set run parameters take data and view the results Control Tabs DGF 4C Online Help 3 Settings Calibrate Run Analyze e Settings The Settings Tab of the DGF 4C Control Panel contains parameters that control the operation of the DGF 4C Most settings are changed on a channel by channel basis The only exceptions are the module control status register Module CSRA and the coincidence pattern which affect the module as a whole The Settings Tab also contains controls used to load save copy
16. n choose a base name and a run number in order to form an output file name The run data will be written to a file whose name is composed of both The run number is automatically incremented at the end of each run if you select Auto update run number on the Data Record Options panel but you DGF 4C Online Help 10 can set it manually as well Data are stored in files in either the MCA folder if the run is a MCA run or the PulseShape folder if the run is a List Mode run These files have the same name as the output file name but different extension as described below For list mode runs buffer data are stored in a file with name extension bin For both list mode runs and MCA runs MCA spectrum data are stored in a file with name extension mca if you select Auto store spectrum data on the Data Record Options panel and module settings are stored in a file with name extension set after each run if you select Auto store settings on the Data Record Options panel Start Run After you have set all parameters you can start a run to take data During the run the Run time time out control shows the remaining time for MCA runs or time out count down for list mode runs If you select multiple spills for list mode runs the number of spills will also count down during the run For list mode runs when the first module reaching the preset maximum number of events stops its run it will also stop the runs in all othe
17. n request several spills or buffer fills For example if you request a run with 10 spills you will get 10 list mode buffers worth of data At start of the first run all previous run history is cleared For instance MCA memory and run and live time information are cleared The next nine sub runs are started with a Resume Run command which leaves previous run information intact Run times and live times and spectra in MCA memory are updated You can also manually adjust the maximum number of events stored before the run is stopped Some data acquisition systems which are geared towards event by event readout and are not able to handle large buffers may benefit from the capability to reduce the maximum number of events per spill Fast List Mode Fast list mode is an event by event data acquisition run without waveforms Since no traces are read out the data acquisition is faster than a regular list mode The data is stored in various formats see section 3 6 of the user manual for details 0x200 full event data 9 words no waveforms 0x201 full event data 9 words no waveforms 0x202 compressed event data 4 words no waveforms 0x203 compressed event data 2 words no waveforms MCA Mode MCA mode puts all modules into a typical spectrum only acquisition mode in which there are no list mode data required The event data is not stored in the output buffer but only used to calculate the energy for incrementing the spectrum Runs end after
18. nnel CSRA Channel CSRB Module CSRB Coinc Coincidence Pattern Coincidence Window MCA Cut Off Energy Binning Factor TAU Tau us After selecting source destination and parameters click on the Copy button to execute the copy operation ExtractPanel Settings gt Extract This panel can be used to extract parameter settings from a file to selected modules and channels The source file is specified at the top of the panel Clicking on the Find button to locate the source file Parameters to be extracted and destination modules or channels are selected in the same manner as in the copy panel Click the Extract button to execute the operation DGF 4C Online Help 7 AllFilesPanel Settings gt Files Paths This panel gives you access to the underlying files of the DGF 4C software Usually these files are already loaded in the memory of the DGF 4C Viewer You only have to change these files when you receive updates from XIA The directory locations are specified as complete not relative search paths the DSP Path for the DSP code and the FPGA Path for the trigger filter FPGA configuration Use a colon as the separator between drive name directory and subdirectories Do not use backslashes For example use D XIA data rather than D XIA data Calibrate Analog Signal Conditioning In the Analog Signal Conditioning section you can set the digital to analog converters DACs in the selected channel and module
19. ns on the neighboring module to the right as seen from the front Setting Bit 10 DSP Trigger Termination terminates the DSP trigger line with 50 Ohm This bit should be set for a module at the end of the trigger bus thus also for a module operated individually Bit 13 Fast Trigger Termination terminates the fast trigger line and should be set for a module at the end of the trigger bus or for a module operated individually Any changes in bits 10 and 13 will be applied to the module when you click the check boxes At startup the bits are set according to the settings file Note Bits 10 and 13 are stored in the DSP memory but do not affect the operation of the DSP They have to be written to the Interface FPGA with a writelCSR command to become effective CCSRAEditPanel Settings gt Channel CSRA Edit Each channel has its own channel control status register Click a check box to set or clear particular bits We give a brief description of all relevant bits here In the CCSRAeditPanel they appear in top to bottom order Bit 0 Group trigger mode This bit controls waveform acquisition To stop the FIFO and store a waveform two conditions must be fulfilled A fast trigger primes the FIFO to stop after a programmed delay but only if by that time a valid trigger is recorded When bit 0 is cleared the source for that valid trigger is the locally generated event trigger of this channel When bit 0 is set the trigger source will be a sign
20. of the preamplifier signal has to be compensated for in order to bring the DC coupled input into the ADC range The exact DC value has no bearing on the acquired spectrum and its origin which is always at zero The DC adjustment is used only to ensure that the signals to be measured fall comfortably into the ADC range When clicking the Adjust Offsets button the DGF 4C Viewer will set the DC offset to a percentage of the full ADC range specified in the Baseline control The offset calibration must be performed with the preamplifiers connected to the DGF 4C inputs and with both the preamplifier power and detector HV switched on One should also repeat the offset calibration each time measurement conditions change in any major way e g when the count rate changes greatly All such changes may influence the DC offset value of the preamplifier signal To analyze the noise spectrum of the acquired trace click on the FFT Display button which opens the FFTDisplay FFTdisplay You can analyze the noise spectrum in the trace captured in the Oscilloscope by observing the Fourier transform of the signal For best results remove any source from the detector and only regard traces without actual events The chart shows a plot of amplitude vs frequency The plot is calibrated such that a sine wave with 100 ADC units amplitude 200 units peak to peak will show up with an amplitude of 100 To convert a noise floor measurement into ADC units sq
21. r modules The Busy Synch connectors need to be connected as described in Module Synchronization if the module operation is to be synchronized Then the data buffer of each DGF 4C module will be read out and saved into a file If more than one spill is requested the run will resume in all modules For MCA runs when the first module reaching the preset run time limit stops its run it will also stop the runs in all other modules Then the MCA histogram of each module will be read out and saved into a file Stop Run If you want to stop a run before it finishes by itself you can click on this button to manually stop it This will end runs in all modules and read out and save the data Data Record Options This panel gives you three options for automating tasks after each run They are all checked by default to ensure all data are saved for each data run Analyze On the top left part of the Analyze tab shows the run time and the measured event rate for the selected module On the right part shows for each channel the fractional live time and the input count rate Note that the run time is the sum of time spent in sub runs called spills but ignoring the time it took the host to read out the data from DGF 4C modules Similarly the live time was measured only while one of the sub runs was ongoing MCA Spectrum Pulse height spectra accumulated in the internal DGF 4C memory can be displayed after pressing the MCA Spectrum button Pulse heights
22. rent FPGA file names for different modules The file name has the format FDGF4C BIN where the first represents the decimation and the second represents the module revision C or D or E So if you have a DGF 4C Rev E module and you want to use a FPGA file with decimation 4 you should put in a file name of FDGF4C4E BIN All the FPGA configuration files are stored in the Firmware subfolder of the DGF4C folder 2 Specify the controller type J73A using Jorway 73A controller CC32 using Wiener CC32 controller Offline for offline analysis without DGF 4C modules attached For the Jorway 73A you have to select the proper SCSI bus number and Crate ID The SCSI ID usually is either O or 1 and may vary between 0 and 7 If it is unknown set it to 0 After system is boot up it will return the correct SCSI bus number and automatically correct it on the DGF 4C Start Up Panel The Crate ID should match the Crate number on the CAMAC crate For CC32 controllers you only need to select the Crate ID which should match the Crate number on the CAMAC crate 3 Choose several advanced options if necessary Check the Fast CAMAC option to use the Level 1 FAST CAMAC transfer if the CAMAC controller supports it In case the main controller can handle Look At Me signals LAMs check the Raise LAMs at the DGF 4C Online Help 2 end of a run The DGF 4Cs can raise a LAM when run data are available to support interrupt driven data read out Leave th
23. rt Hz use the variable FFTbin displayed at the top of the chart which tells the width of each frequency bin in the Fourier spectrum The conversion from amplitudes to rms ADC units sqrt Hz is accomplished by multiplying with 1 sqrt 2 FFTbin Now observe that an ADC unit corresponds to 61nV Rev E or 244uV Rev D Using the known gain of the DGF 4C you can convert the noise into an input noise voltage density measured in V sqrt Hz Or given a particular energy calibration the noise density can be expressed as eV sqrt Hz If you click on the Apply Filter button you can see the effect of the energy filter simulated on the noise spectrum Run Run Type This popup menu is used to set the run type to one of the following modes List Mode List mode is the general data acquisition run Waveforms energies and time stamps are collected on an event by event basis The data is stored in various formats see section 3 6 of the user manual for details 0x100 full event data 9 words plus waveforms 0x101 full event data 9 words no waveforms 0x102 compressed event data 4 words no waveforms 0x103 compressed event data 2 words no waveforms Since available memory limits the number of events that each module can store in its buffer the DGF DGF 4C Online Help 9 4C Viewer computes the maximum number of events When the maximum is reached the run is stopped and the buffer is read out For a longer run in list mode you ca
24. s the untriggered signal input Click Refresh to update the display The pulses should fall between 10 and 90 on the right axis If no pulses are visible or if they are cut off above 100 or below 0 click Adjust Offsets to automatically set the DC offset There is a control called Baseline on the Oscilloscope which can be used to adjust the DC offset for each channel If the pulse amplitude is too large to fall in the display range decrease the Gain in the Calibrate tab of the DGF 4C Control Panel Since the offsets might drift for example after changes in input count rate it is useful to leave the display open and check the offsets once in a while In the Calibrate tab input an estimated preamplifier RC decay time for Tau in us then click on Find to determine the actual Tau value for the current channel of the current module Repeat this for other channels if necessary The Tau finder works best for a Tau value from 20 us to 200 us In the Settings tab click on Save to save the system parameters found so far You can save the settings into either an existing settings file or a new file 4 Click on the Run tab set Run Type to 0x301 MCA Mode Polling time to 1 second and Run time time out to 30 seconds or so then click Start Run After the run is complete select the Analyze tab and click on the MCA Spectrum button The MCA spectrum shows the MCA histograms for all four channels You can dese
25. se variables Use the mouse to zoom in on peaks of interest In the max and min fields you can select a fit range Gauss fit will produce a Gaussian fit with constant background Displayed results are the area under the peak and the energy resolution Again the min and max variables are stored for each channel
26. the time specified in the RunTime TimeOut control counts down to zero The Maximum no of Events control is set to zero for MCA runs since it is not used to end the run Polling Time The polling time indicates the time interval at which the DGF 4C Viewer checks if the run in the selected modules has ended If so runs are stopped in all modules if they have not stopped already and the data are read out Run Time Time Out This variable is used to indicate the total run time for MCA runs or the timeout limit for list mode runs Number of Spills The variable indicates the number of repeated runs It is only used in list mode runs Maximum no of Events This variable indicates the maximum number of list mode events the DGF 4C module can store in its buffer for each run Synchronization The first check box asks if all modules should start and stop simultaneously In almost all multi module systems this will be the case and the box should be checked For this to work all Busy outputs on the front panel of DGF 4C have to be connected to a common OR gate whose outputs must be sent to all Synch inputs on the DGF 4C front panels NIM signal levels If you also want all timers in all modules to be reset with the start of the next data acquisition run click the box Synchronize clocks For this feature to be useful all DGF 4C modules should be operating from the same master clock as described in the user s manual Output File You ca
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