Cinabro, D

Dubrovin, M

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CBN 00-7CBX 00-28M.DubrovinD.Cinabro25 April 2000CLEO Silicon PIN-Diode Radiation Monitor System:CLEO III Engineering Run1 IntroductionThe CLEO radiation monitor system that was used during the CLEO III engineering run,October 1999 through February 2000, is reviewed. We describe the upgraded PIN-DiodeRadiationMonitor system. We have paid much attention to the calibration, understandingits stability, and the precision of the dose measurement. Only a slightly altered system isused for the CLEO III physics run.2 Location of sensorsThe detectors of the PIN-Diode Radiation Monitor consists of 24 PIN diodes (Siemens,type SFH 206K) which are located in two aluminum rings at a radius of 2.4 cm fromthe beam axis shown in Figure 1 and at a distance 14 cm to the west and east of theZenith7Nord1410235689 1112φ(CLEO)φ (CESR)Pin-diodesFigure 1: PIN-diode orientation and numbering in their retainer rings.1interaction point. On each side the monitors are numbered from 1 to 12, with 1 being onthe north (inside of the CESR ring), 3 being on the top, etc.3 ElectronicsThe general scheme of the electronics for each of the 24 channels is shown in Figure 2.To extend the dynamic range of the monitor by a factor of 10 the output is split into two~4 ADC count/mV x 1.5ADCADCF~10m~1V/nA x10Figure 2: General scheme of the PIN-diode radiation monitor electronics.parts; one that passes through a second gain stage (x10) and another with no change tothe initial gain. A detailed schematic of the integrating ampliers is shown in Figure 3.The output of the ampliers goes to a lter whose schematic is shown in Figure 4. Two 2.5nFIn Out-15V+15VTL031ACP0.1 6.8100M10k10kFigure 3: Schematic of the integrating am-plier.gOutC i C oIn RRsFigure 4: Schematic of the lter.simple circuits shown in Figure 5 and Figure 6 are used for calibration of channels inI~1nA10 k 100 M1 kU~1VFigure 5: Calibration circuit for currentmode.10pFdU=10V dq=100pC50 ohmFigure 6: Calibration circuit for chargemode.current amplication and charge amplication mode respectively.24 SoftwareSeveral stand-alone routines related to Radiation Monitors are located at CESR24 com-puter in the directory USER$DISK:[CLEO21.CLEOSIRAD].Three new routines have been developed to have easy access to Radiation Monitordata: RDB.* reads the contents of several les stored in the CESR data base. Record arestored in the data base at the rate of one per minute. The program extracts morethan 100 parameters, and puts them in Ntuple RADMON.TUP. The program readsthe records for a specied day. ROL.* creates the same Ntuple RADMON.TUP, but reads the radiation monitorson-line, with a rate of one record per second. The number of records to read isinquired at the start of the routine. DOSEINT.* integrates the accumulated dose between two dates specied at startof the routine. Dierential and integrated dose for each channel and their averagevalue are stored in Ntuple DOSEINT.TUP, one record per day.Several helpful PAW scripts (KUMAC-les), located in the daughter directoryUSER$DISK:[CLEO21.CLEOSIRAD.PAWIAN], allow us to have convenient access to theabove Ntuples and draw graphical pictures of monitor response.5 CalibrationThe small value of the measured currents from the PIN diodes and the high gain of theampliers imply that careful attention must be given to calibration. The rst approachplaced an additional resistor of 1 Mohm parallel to the amplier input to generate a smallcurrent signal. This shifted the output base level > 100% with respect to the signal. Toeliminate the inuence of the circuit on the calibration the resistor has been increased upto 100 M. Dynamic calibration has been also done to insure that the calibration circuitdoes not change the gain of the amplier.5.1 Measurement of injected test currentInjected current, generated by the circuit shown in Figure 5, is measured with a picoamp-meter as a function of input voltage. Figure 7 shows the linearity of the response and theresiduals from the linear t. The residuals demonstrate, that the injected current can beadjusted with a precision of  1 pA. Based on the calculated PIN-diode response currentfor dierent \round values" of radiation dose, the corresponding input voltages have beenchosen. The results are listed in Table 1.5.2 Components of the ltersTo check that the lters, shown in Figure 4, are in a good working condition, theirparameters have been measured separately. The results are listed in Table 2.3-2000-1200-40040012002000-2 -1.5 -1 -0.5 0 0.5 1 1.5 2Uinput , VI output , pA  0.1224P1  0.1534P2   884.5-1-0.500.51-2 -1.5 -1 -0.5 0 0.5 1 1.5 2Uinput , V∆Ioutput , pAFigure 7: Dependence of the injected current, and residuals from the linear t shown,on voltage applied in the calibration circuit shown in Fig 5.Table 1: The relation between the injected current, dose expressed in dierent units, andthe input voltage on the calibration circuit.Injected current Dose per single PIN-diode Input voltage, V2.85 pA 1 rad/hour |285 pA 100 rad/hour = 1.667 rad/min = 27.8 mrad/s 0.3231 nA 351 rad/hour = 5.85 rad/min = 97.5 mrad/s 1.131171 pA 1 rad/min 0.1945.3 Parameters of the Second Stage Filtered AmpliersThe gain coecients of the second stage Filtered Ampliers have been measured at aninput level 1 0:002 V . The results are listed in Table 3. The gains are equal to 10 withprecision  3%. The observed dynamic range for their output is about 14 V .5.4 Calibration of the gainThe response of the ampliers and the ADCs is sequentially measured for the test inputcurrent 0 pA and 285 pA, corresponding to a dose rate of 100 rad/hour/PIN diode.4Table 2: Measured lter parameters. Rs{ resistance between signal pins of input andoutput connectors; Rg{ resistance between grounds of input and output connectors; Cout{ capacitance, measured at output connector; Ci{ internal capacitance, measured directlyin circuit.Upper box, WestN Rs; k Rg; k Cout; F Ci; F1 104.3 106.2 1.11 1.122 104.2 105.4 1.06 1.143 105.3 107.2 1.12 1.094 108.0 105.4 1.16 1.115 104.1 103.1 1.09 1.066 106.6 104.7 1.08 1.107 104.5 105.1 1.08 1.118 106.9 103.1 1.05 1.099 106.7 106.2 1.08 1.1010 104.8 106.6 1.13 1.1311 106.4 105.8 1.06 1.1312 105.4 108.0 1.02 1.13Lower box, East1 107.4 107.0 1.10 1.132 106.4 106.7 1.07 1.123 105.3 104.9 1.10 1.114 104.4 107.3 1.12 1.125 106.4 104.8 1.10 1.166 106.0 103.6 1.12 1.157 106.7 105.1 1.14 1.128 104.4 105.4 1.11 1.119 107.2 106.3 1.11 1.0610 104.8 102.7 1.12 1.1111 104.9 103.2 1.08 1.0812 103.4 102.6 1.12 1.12To take in to account the shift of the base level due to the inuence of the calibrationcircuit the responses for both signs of current was used. The typical responses of the westring channels, for example, during the calibration are shown in Figure 8. The measuredresponses of the ampliers and the ADCs are listed in Table 4. The calculated calibrationcoecients are shown in Table 5 and in Figure 9. The pedestal is dened as the signallevel when there is no beam in or no injection to CESR. Comparison of the calibrationcoecients from Table 5 with previous calibration, taken four days earlier and shown inTable 6, shows that the pedestal and signal response uctuations are random and do notexceed 4 ADC counts. This value is considered the stability of calibration coecients.As discussed above the calibration circuit shifts the amplier base level about -2 mVwhich corresponds to a pedestal shift of -10 ADC channels. This correction is used in thecalculation of the conversion coecients.5Table 3: Measured voltage gain for the Gain 10 Filtered Ampliers. Input voltage atmeasurement was set equal to 1 V with precision of 0.2%.N Upper box, West 1{8 Middle box, West 9{12, East 1{4 Lower box, East 5{121 9.95 9.95 9.812 10.04 10.06 9.783 9.99 10.17 9.804 9.94 10.58 10.855 9.99 10.26 9.796 10.00 9.90 9.627 10.00 9.89 9.778 9.94 9.89 9.80Table 4: Response of ampliers, high and low gain ADC channels on an injected currentof 285 1 pA, corresponding to 100 rad/hourChannel Amplier response High gain channels Low gain channelsNo. mV mV ADC count ADC count ADC count ADC count1W 251 -258 1524 -1503 150 -1532W 257 -264 1587 -1523 153 -1583W 261 -265 1582 -1563 156 -1584W 258 -264 1563 -1536 154 -1585W 257 -264 1551 -1565 153 -1586W 258 -264 1569 -1548 153 -1587W 249 -255 1516 -1500 148 -1538W 258 -263 1549 -1554 154 -1589W 253 -258 1542 -1487 150 -15510W 253 -262 1551 -1541 151 -15611W 248 -256 1524 -1539 147 -15312W 248 -253 1608 -1553 148 -1501E 247 -253 1528 -1542 147 -1502E 269 -273 1599 -1607 160 -1623E 251 -255 1486 -1511 148 -1524E 240 -249 1446 -1440 142 -1475E 258 -261 1516 -1526 153 -1556E 262 -265 1534 -1557 156 -1587E 263 -265 1542 -1547 156 -1588E 252 -257 1641 -1656 150 -1539E 247 -254 1455 -1485 147 -15210E 260 -264 1429 -1431 154 -15811E 259 -266 1518 -1556 154 -15812E 271 -271 1581 -1595 160 -1616Radiation Monitor Calibration22/12/99   12.39-200002000W1-200002000W7-200002000W2-200002000W8-200002000W3-200002000W9-200002000W4-200002000W10-200002000W5-200002000W11-200002000W6Time, secADC counts-2000020000 100 200 300W12Time, secADC countsFigure 8: High gain channel response during the calibration procedure.Within the precision of the digitization, all circuits demonstrate the linear responseto injected test current.5.5 Charge calibration of amplierCharge calibration has been done in order to verify that the calibration circuit in Figure 5does not inuence the amplier gain. This approach also allows us to measure the timing7Table 5: Calibration coecients for PIN-Diode Radiation Monitor electronics channels.Amplier High gain channels Low gain channelsChannel Gain, Pedestal, Gain, Dose coef., Gain, Dose coef.,No.VnAADC countADC countmVmradminADC countADC countmVmradminADC count1W 0.893 19 5.95 1.101 0.595 11.02W 0.914 43 5.97 1.072 0.597 10.73W 0.923 16 5.98 1.060 0.597 10.64W 0.916 22 5.94 1.076 0.598 10.75W 0.914 4 5.98 1.070 0.597 10.76W 0.916 19 5.97 1.069 0.596 10.77W 0.884 16 5.98 1.105 0.597 11.18W 0.914 6 5.96 1.074 0.599 10.79W 0.896 37 5.93 1.100 0.597 10.910W 0.904 18 6.00 1.078 0.596 10.911W 0.884 6 6.08 1.088 0.595 11.112W 0.879 36 6.31 1.055 0.595 11.21E 0.877 3 6.14 1.086 0.594 11.22E 0.951 4 5.92 1.040 0.594 10.43E 0.888 -3 5.92 1.112 0.593 11.14E 0.858 15 5.90 1.155 0.591 11.55E 0.911 1 5.86 1.096 0.593 10.86E 0.925 -3 5.87 1.078 0.596 10.67E 0.926 3 5.85 1.079 0.595 10.68E 0.893 1 6.48 1.011 0.595 11.09E 0.879 -3 5.87 1.134 0.597 11.110E 0.919 4 5.46 1.166 0.595 10.711E 0.921 -9 5.86 1.084 0.594 10.712E 0.951 -5 5.86 1.050 0.592 10.4parameters of the ampliers and to estimate their voltage-to-charge and voltage-to-currentgain factors.Rectangular pulses from Datapulse 100A Pulse Generator with amplitude Uin=+10 V, duration  100 ms, and repetition time 2.5 s were used as input the the cali-bration circuit shown in Figure 6. This circuit inject the charge q = CUin= 100 pCinto the amplier at each front of rectangular pulse. Typical oscilloscope diagram ob-served at exit of the amplier with 50 ohm termination is shown in Figure 10. There islittle response variation from channel to channel. Based on this diagram, main param-eters of the amplier can be estimated. Each front gives the jump of the output levelUout= 300 mV+345 mV. Relaxation time is estimated to be  = 250 ms. Hence, the charge tovoltage and current to voltage gain factors could be evaluated:G(q ! V ) = Uout=q = 3:45 mV=pC;8cal.1999121600.20.40.60.811.24 8 12West Channel No.Gain , mrad/min /ADC count00.20.40.60.811.24 8 12East Channel No.Gain , mrad/min /ADC count0510152025303540454 8 12West Channel No.Pedestal, ADC count-8-404812164 8 12East Channel No.Pedestal, ADC countFigure 9: Gain coecients and pedestals for the radiation monitor system.G(I ! V ) = Uout =q = 0:86 V=nA:Within precision of measurement the last gain factor coincides well with data obtainedfrom normal current calibration shown in Table 5.6 Temperature dependence of pedestal levelA dedicated study has been done to estimate the dependence of pedestal level on tem-perature of the beam pipe close to the PIN-diodes location. This was a problem in theCLEO II.V era when the same radiation monitor system was in place. The temperatureof the beam pipe was changed steadily by varying the set point on the CLEO beampipecooling system from 20 to 26oC. The mean temperature for dierent groups of beam-pipe9Table 6: Response and calibration coecients for PIN-Diode Radiation Monitor high gainelectronics channels, measured on December 16, 1999, at injected current  285  1 pA,corresponding to 100 rad/hour.Channel Pedestal, Response, k,N ADC count ADC countmradminADCcount1W 19 1525 1.0992W 43 1590 1.0703W 16 1584 1.0564W 22 1566 1.0735W 4 1554 1.0686W 19 1570 1.0687W 18 1519 1.1038W 6 1551 1.0729W 37 1543 1.09910W 18 1554 1.07811W 6 1527 1.08912W 36 1609 1.0531E 3 1530 1.0842E 4 1605 1.0353E -3 1491 1.1084E 15 1450 1.1535E 1 1519 1.0916E -3 1537 1.0757E 3 1545 1.0748E 3 1645 1.0099E -2 1459 1.13310E 4 1432 1.15911E -8 1521 1.08312E -5 1584 1.042thermocouple sensors during this period is shown in Figure 11. Corresponding variationof pedestal level measured for few high gain channels of radiation monitor is shown inFigure 12. Some channels show very slow dependence  1 ADC count/5oC, that is smallcompared to the stability of the gains. Variation of the beam-pipe temperature duringCESR runs, for example see Figure 13, does not exceed 2oC. The temperature dependenceis negligible and no correction is made for it. Apparently the new PIN-diodes have a muchreduced dark current versus temperature, the source of the temperature dependence inthe old system.10time110 ms250ms-0.3 V-0.21 V+0.135 VFigure 10: Typical response of the amplierfor short charge signals, obtained with cali-bration circuit shown in Fig 6.7 Correlations of monitor response with a beamcurrentIt is important to show that the radiation monitor system really sees the radiation frombeam current in CESR rather than being dominated by background uctuations.The response one of the radiation monitor channels is shown in Figure 14 as a functionof time. The radiation signal accurately tracks the beam current. The bottom two plotsin Figure 14 show the correlations between beam current and response of the rst channelfor west and east rings. The correlation is obvious and we conclude that the PIN-diodeRadiation Monitor can be used for optimization of CESR beam induced background inCLEO.8 Integrated doseBased on calibration coecients listed in Table 5 we calculated the integrated radiationdose for the CLEO III engineering run November 6, 1999 through February 7, 2000.Shown in Figure 15 is the integrated dose averaged over all PIN-diodes versus time. Thehistograms show the total integrated dose on each PIN-diode. The enhancement in themedian plane of the ring is evidence for a substantial amount of synchrotron radiationbeing scattered o the masks tips at 25 cm from the interaction point.9 ConclusionThe radiation monitor system at the end of the CLEO III engineering run is in a goodworking condition. The calibration of the electronics channels has been done and the pro-cedures are easy to repeat to monitor the system. The integrated dose can be calculatedfor any desirable period of time. The only change in the system is to install a new set ofPIN-diodes that were long ago installed on the CLEO III beryllium beam pipe, aroundwhich the Si3 was built. The environment of the diodes will change. Instead of being11Temperature variation20222410 12 14West inner sensorsTime, hoursMean T, degree C2022242610 12 14West outer sensorsTime, hoursMean T, degree C2022242610 12 14East inner sensorsTime, hoursMean T, degree C2022242610 12 14East outer sensorsTime, hoursMean T, degree C2021222324252610 11 12 13 14 15All beam-pipe sensorsTime, hoursMean T, degree CFigure 11: Variation of the beam-pipe temperature. Each point corresponds to1 min.behind the 1/8" of aluminum of Pipe 0, they will be behind a thin beryllium pipe anda thin layer of gold. Every other diode will be shielded from synchrotron radiation by a0.1 mm layer of platinum to allow us to observe the synchrotron radiation signal directlyby subtraction.12HW01  VS  NREC/6018.819.620.421.2HW07  VS  NREC/601819HW02  VS  NREC/604546HW08  VS  NREC/6046HW03  VS  NREC/601819HW09  VS  NREC/603638HW04  VS  NREC/602224HW10  VS  NREC/60212223HW05  VS  NREC/60910HW11  VS  NREC/601012HW06  VS  NREC/60212212 14Time, hoursADC countsTMEAN.F  VS  NREC/60202412 14Time, hoursMean T, degree CFigure 12: Variation of pedestals as the beampipe temperature is varied. Occasionlythe pedestals uctuate by 2 ADC count due to a 1.5 gain factor applied to the rawsignal to the read ADC response.1301000 2 4 6 8 10Time, hourI- , mA01000 2 4 6 8 10Time, hourI+, mA02000 2 4 6 8 10Time, hour∑I , mA2324250 2 4 6 8 10Time, hourT, degree CFigure 13: Beam currents and mean beam-pipe temperature during the owl shift of12/20/99.1402000 2 4 6 8Time, hour∑I , mA203040500 2 4 6 8Time, hourW1, ADC count1620242832364044480 200 ∑I , mAW1, ADC count4812162024280 200 ∑I , mAE1, ADC countFigure 14: Correlations of radiation monitor response with beam current. Eachpoint corresponds to 1 min. Data from owl shift 12/20/99.1501002003004005006007008000 2 4 6 8 10 12Nov 8, 1999 - Feb 4, 2000Week< Dose / Pin-Diode > , radWest Ring040080012000 100 200 300ΦCESR , degreeDose / Pin-Diode , rad East Ring0500100015000 100 200 300ΦCESR , degreeDose / Pin-Diode , radFigure 15: The PIN-diode radiation monitor dose integrated during the CLEO IIIengineering run. The upper plot shows the average dose versus time and the lowerhistograms shows the total integrated does on each diode.16

CLEO Silicon PIN-Diode Radiation Monitor System: CLEO III Engineering Run

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