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Multichannel Scaling (MCS)

4 Multichannel Scaling (MCS)

This mode is for semi-automated measurements of time distributions with any radiation
detector (HPGe, NaI, CdTe, CdZnTe and neutron counters). The software used for this is
WinMCS. 
It allows to measure a time distribution of count rates, and in case of a spectroscopical
detector, measurement of an integral spectrum at the same time.
Input can be set to the following:

•

TTL input (no spectrum possible in this case)

•

Input rate (corresponds to the fast count rate of MCA measurements)

•

LLD/ULD (corresponds to the content of a partial region of a spectrum, defined by
the lower end LLD and the upper end ULD. 

New compared to MCA166 is that the MCA527 principally supports dwell times down to
100µs, whereas the MCA166 was limited to 10ms minimum. Also the MCA527 allows up
to 16k time channels, where the MCA166 was limited to 4k.
However,   100µs   dwell   time   and   16k   channels   will   be   only   supported   with  WinMCS
versions >2.0.

49

Содержание MCA-527

Страница 1: ...nel Analyzer GBS Elektronik GmbH Bautzner Landstra e 22 01454 Gro erkmannsdorf Germany Tel 0049 0 351 21 70 07 0 Fax 0049 0 351 21 70 07 21 E Mail kontakt gbs elektronik de Website www gbs elektronik...

Страница 2: ...this manual has been carefully reviewed and is believed to be accurate and reliable However the GBS Elektronik GmbH assumes no liabilities for inaccuracies in this manual This manual is subject to ch...

Страница 3: ...High Voltage 16 2 2 9 Exchanging the High Voltage Module 18 2 2 10 Functions of the D SUB9 connector 18 2 2 11 Extension Port 20 2 2 12 Connector Pinouts 21 2 2 13 Accessories 24 2 3 MCA527OEM Specifi...

Страница 4: ...ope Mode 50 5 2 Auxiliary Measurements 50 5 2 1 Supply Currents 50 5 2 2 Internal Temperature 51 5 2 3 Detector Temperature 51 5 2 4 Additional Analog Voltage 51 6 Software 52 6 1 Overview 52 6 2 WinS...

Страница 5: ...echnical Data 58 8 1 MCA527 Hardware Specifications 58 8 1 1 Absolute Maximum Ratings 58 8 1 2 Operational Ratings 58 8 2 Block Diagram of the MCA527 63 9 Troubleshooting 64 10 Firmware Update 67 A MC...

Страница 6: ...d multi channel scaler analyzer e g WinMCS Additional user programs which support safeguards specific applications as U235 enrichment verification spectral radiation survey meter mode supporting activ...

Страница 7: ...uctor detector which converts an absorbed photon directly into a small charge quantity Or it can be a scintillation detector which converts an absorbed photon into visible light which is then converte...

Страница 8: ...he device can be powered directly from a high power USB port up to the maximum nominal input power of 2 5W The supply voltage for the MCA is nominal 12V with a tolerance range of 2V Do not apply more...

Страница 9: ...riodically transferred via a communication interface to the computer The computer is used to setup the MCA527 to display and process the measurement results and to store the data The design concept of...

Страница 10: ...527 turns on automatically 2 2 2 LED Indicators The LEDs indicates the actual device state even if no computer is available or located far away from the MCA All possible states are shown in Figure 2 T...

Страница 11: ...detector high voltage together with the preamplifier power supply will be switched off Now the user can transfer the measured spectrum to the computer but should switch the device off afterwards or c...

Страница 12: ...out detector or with a low power detector e g CdZnTe or NaI If a detector draws to much power from the MCA527 e g some HPGe charging via USB is still working but the battery runs out slowly There are...

Страница 13: ...hat the new batteries have exactly the same voltage charge state The voltage difference must never exceed 0 5V otherwise there is the danger of battery destruction It is also possible to operate the M...

Страница 14: ...ower supply has the correct polarity and that the power consumption of the detector does not exceed the maximum ratings of the high voltage power supply module 0 5mA or 0 25 Watt Checking the high vol...

Страница 15: ...een at a detector preamplifier output here from a CZT500 detector For optimum performance the rise time should be in the order of 100ns and decay time constant of 50 s This is drop to 36 8 of peak val...

Страница 16: ...he HV is needed for the operation of the photomultiplier The photomultiplier acts as some kind of amplifier whose amplification is strongly dependent on the high voltage setting Therefore it is necess...

Страница 17: ...00V is still above the depletion point it is no problem to use this detector with lower voltage However it is not possible to estimate the depletion voltage from the detector nominal voltage this has...

Страница 18: ...detectors CZT behave somehow similar to HPGe Centroid position depends rather weak on HV setting Choosing a too low voltage effects that charge loss processes become more dominant and therefore the p...

Страница 19: ...connector By turning on the internal current source a constant current of about 500 A is fed into the thermistor and the resulting voltage is measured with the ADC on pin 5 see Figure 6 The applicatio...

Страница 20: ...power the transceiver is disabled by default Part B is a 3 3V digital output with output enable It can be used as general purpose output or as TTL UART TxD Part C is a 3 3V digital input which is 5V...

Страница 21: ...ion In conjunction with the calibrated built in current source it is well suited for measuring external resistors in the range of 0W 8kW This feature allows easy analyzing of a thermistor or any other...

Страница 22: ...blank out specific pulses e g LED pulses from a LED stabilized NaI detector It accepts 3 3V TTL pulses but is also 5V tolerant This connector is only available in the MCA527 and not in the MCA527L Tab...

Страница 23: ...for future extensions e g connecting a GPS receiver Other applications are integrated on request This connector is only available in the MCA527 and not in the MCA527L Table 6 Pinout of the Extension P...

Страница 24: ...ting the MCA527 to a Computer with USB port MCA527 MCA527L Cable MCA Pocket PC RS232 For connecting the MCA527 to a Pocket PC with RS232 interface and special connector on request Cable MCA PC Etherne...

Страница 25: ...ersion needs an input voltage of 4 5V to 9V Powering the MCA527OEM through the USB port is not possible MCX coaxial connectors Teleg rtner J01271A0131 series J0127 are used for the signal input the ga...

Страница 26: ...on port 2 shield RS232 interface 3 RxDext RS232 extension port 4 RxD RS232 interface 5 GNDext extension port 6 GND RS232 interface 7 TxDext RS232 extension port 8 TxD RS232 interface 9 10 13 15 not co...

Страница 27: ...surement values with a fixed row of numbers and adding up all the results This row of numbers is the digital filter A signal processor is especially designed to perform such a task Also with a digital...

Страница 28: ...r should be adjusted such that the result is invariant to a shift of 100ns forward or backward This correction is also derivated from the pole zero setting 3 2 Adjustments and Settings 3 2 1 Input Pol...

Страница 29: ...differentiation Even more sensitive is the 1 0 1 filter which checks the difference between incoming signals of 200ns distance The best pulse pair resolution ability to distinguish between close follo...

Страница 30: ...ound and therefore a reason to readjust trigger level Some software allows this Symptoms of too low trigger level are There is a unusual high count rate with some detector and no sources present Left...

Страница 31: ...and sometimes as pile up peak at exactly double energy Recognizing pile up is task of the trigger logic The ability to prevent pile up depends very much on the time resolution and therefore on the use...

Страница 32: ...0 7 s and for a NaI 0 2 s The best shaping time to set depends also on expected count rate For higher count rates a lower shaping time is useful as pile up probability and necessary processing power...

Страница 33: ...s seem to be optimum 0 1 1 0 10 0 10 0 12 0 14 0 16 0 18 0 20 0 22 0 24 0 26 0 28 0 30 0 1st measurement 2nd measurement MCA166 for comparison Shaping Time s FWHM 662keV keV Figure 14 Dependence of r...

Страница 34: ...he ADC is bandwidth limited there is a finite rise time of around 300ns even for infinitely fast rising signals settling time may be twice as long Therefore the shortest useful flattop time may be 0 6...

Страница 35: ...s the base line is at 10 of the ADC range and for negative signals the base line is at 90 of the ADC range 35 Figure 16 Dependence of resolution on flattop setting using a NaI detector As a NaI detect...

Страница 36: ...s window of the software There the spectroscopical filter is applied to the signal before and after a voltage step but where the result should be zero The difference between those both measurements is...

Страница 37: ...time constant of the preamplifier and therefore there is only one adjustment parameter which adjusts both for pole zero and jitter Misadjustments will cause characteristic deformations of the peak sh...

Страница 38: ...tribution the FWTM FWHM ratio is significantly smaller here and resolution is generally worse The wrong pole zero does not really affect as the count rate is very low Figure 21 Measuring Cs137 with di...

Страница 39: ...should not change to fast it is possible to do averaging There are settings from 1 to 32 possible 1 means no averaging and the baseline value always new measured 32 is that the last measured value co...

Страница 40: ...ng of the second derivate This should increase the timing accuracy to something like 10ns 20ns The amplitude is then correspondingly interpolated Jitter correction may give a resolution improvement in...

Страница 41: ...s filter gives best results with twice or triple as high shaping times so throughput may be a bit limited with this Resolution can be almost as good as with the standard filters in a quiet environment...

Страница 42: ...ined Settings shaping time 6 s flattop 0 8 s BLR32 Right 60keV peak of Am241 measured in a very noisy environment Settings same as figure on the left The resolution degrades from 0 49keV to 20keV meas...

Страница 43: ...a NaI typically 512 channels are enough Default is 4k with MCA527 and 1k with MCA527L MCA527L offers only up to 2k channels 3 2 15 Threshold This setting is a legacy of MCA166 where the default setti...

Страница 44: ...PGe EGC 30 190R Eurisys 3000 pos 4096 4 HPGe EGPC 25 185 Eurisys 2000 neg 4096 4 Table 13 Further settings optimized for different count rates as example a coaxial HPGe shaping time flat top trigger f...

Страница 45: ...lace Stabilization is mostly used with temperature sensitive detectors such as NaI and for long term or series measurements For stabilization a peak has to be selected from spectrum which should be al...

Страница 46: ...abilization area to 1500 should yield the best results 3 5 Direct Input Pulse Height Analysis This mode is useful when dealing with Gaussian pulses which may be the output of a shaping amplifier or de...

Страница 47: ...Time Calculation Dead time calculation is a crucial task when doing high rate measurements and still expecting accurate quantitative measurement results Dead time with MCA527 has several components A...

Страница 48: ...de which allows to start immediately the next measurement while transferring the data of the previous spectrum simultaneously 3 6 3 Autonomous Repeat Mode Autonomous repeat mode is a still to be imple...

Страница 49: ...Input can be set to the following TTL input no spectrum possible in this case Input rate corresponds to the fast count rate of MCA measurements LLD ULD corresponds to the content of a partial region...

Страница 50: ...d measurements down to the V level are possible 5 2 Auxiliary Measurements 5 2 1 Supply Currents The diagnostics menu of each program shows the primary currents of the preamplifier power supply 12V an...

Страница 51: ...face such as DS1822 connected to pin 8 of the D SUB9 preamplifier power supply connector If such a sensor is found its temperature is displayed in the diagnostics menu and saved with the spectrum Seco...

Страница 52: ...brief descriptions of the programs You can find more detailed information on the CD delivered together with the device You should also use the online help of each program 6 2 WinSPEC 2 0 First softwar...

Страница 53: ...asurements Special features of WinSPEC A are Automatic restart of the program after lost of mains power program or operating system crash Sending commands to a special hardware module on LPT1 for moni...

Страница 54: ...integral spectrum but one spectrum for every point so it is possible to evaluate courses off arbitrary net or integral ROI areas 6 5 MCAtouch Software made for safeguards purposes The focus here is o...

Страница 55: ...APrint MCAPlot and MCAPrint are programs to view and print spectra Up to 32 spectra can be viewed at the same time and be printed on one page Also some evaluation functions are available MCAPlot is no...

Страница 56: ...rwinner spc Target dat dat 2 column energy channel content de1 Canberra S100 dat Silena Gamma 2000 spk R ntgenanalytik spa Sarad usf URSA 6 7 Miscellaneous For communication and evaluation some librar...

Страница 57: ...1173 23 1332 49 99 85 99 98 Co57 271 8d 14 4 122 06 136 47 9 16 85 6 10 68 Cs137 30 07y 661 66 85 1 Eu152 13 3 y 121 77 344 28 778 91 964 11 1112 07 1408 00 28 38 26 59 12 98 14 46 13 57 20 85 Hg203...

Страница 58: ...5V to 6 5V Output Voltage O1ext TxDextTTL O2ext to GNDext 0 5V to 6 5V Clamp Current O1ext TxDextTTL O2ext to GNDext 50mA Input Voltage RxDext to GNDext 25V Output Voltage TxDext to GNDext 13 2V Short...

Страница 59: ...changeable in steps of 0 1 s Fine Gain Adjustment 0 5 to 6 5 changeable in steps of 0 01 Channel Splitting 128 256 512 1024 2048 4096 8192 16384 128 256 512 1024 2048 Differential Non Linearity 1 for...

Страница 60: ...Voltage Inhibit Input5 available not available First Auxiliary Analog Input6 0V to 10 23V 11bit resolution not available Second Auxiliary Analog Input7 0V to 10 23V 11bit resolution not available 1 Wi...

Страница 61: ...5 2 3V 24mA15 Digital Output Voltage Low O1ext TxDextTTL O2ext 0 1V 100 A15 0 6V 24mA15 Digital Input Voltage Range I1ext RxDextTTL I2ext 0V to 5 5V15 Positive Going Input Threshold Voltage I1ext RxDe...

Страница 62: ...the D SUB9 connector Can be used to connect different sensors 8 Available at pin 8 of the D SUB9 connector Can be used to connect external temperature sensors 9 Temperature is shown in diagnostics me...

Страница 63: ...Technical Data 8 2 Block Diagram of the MCA527 63 Figure 27 MCA527 Block Diagram...

Страница 64: ...regardless if the switch is on or off MCA battery empty Charge MCA battery 3 MCA lamp flashes irregularly Computer tells MCA power failure or beeps MCA battery very low Charge MCA battery MCA internal...

Страница 65: ...shoot or ringing Try to use another preamplifier or just switch the pile up rejector off Similar effects can be seen if detector cables longer than 50m are used 7 Dead time shown is very high although...

Страница 66: ...count rate Keep a bigger distance to radiation source Try a less sensitive detector Watch for your personal safety Check detector Check for disturbances of switch mode power supplies etc Typical erro...

Страница 67: ...Micro with different hardware versions If you are unsure about the variant and the hardware version of your MCA527 look for this information within the diagnostics dialog of for example WinSPEC When...

Страница 68: ...is determined by averaging 4 points on both sides of the peak the ROI limit points and 3 outer points and linear fit where Spectrumi the absolute number of counts in channels i ROIbegin the ROI s star...

Страница 69: ...s fall below the half maximum channel It is now made sure that the following channel e g 1204 also falls below the half maximum channel The same algorithm is applied for the other side of the peak The...

Страница 70: ...spectrum Spectrumx Count content of channel i in the spectrum to be subtracted F Strip factor E calibration The Energy calibration allows to convert the x axis channel numbers into energy values in K...

Страница 71: ...Data Format MCA_Spectral_Data_Format_XXXX_XX_XX pdf Description of the MCA527 Firmware Commands MCA527_Firmware_Commands_XXXX_XX_XX pdf Description of the MCA Communication DLL MCA_Communication_DLL_X...

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