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THERMAL STEPS ANALYSIS

THERMAL STEPS ANALYSIS. Goals & Means : apply a “step function” on the cooling water look at : APD response with laser runs APD+crystal response with beam runs get : APD gain variation with temperature crystal change in scintillation with temperature characteristic time of the system

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THERMAL STEPS ANALYSIS

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  1. THERMAL STEPS ANALYSIS • Goals & Means : • apply a “step function” on the cooling water • look at : • APD response with laser runs • APD+crystal response with beam runs • get : • APD gain variation with temperature • crystal change in scintillation with temperature • characteristic time of the system • Outline : • method used • steps performed • analysis • Laser (step #3) • Beam (step #1 & 2) Julien Cogan CERN/EP/CMA

  2. METHOD • Beam runs : • cut on beam chambers (3 mm radius around beam center) • reconstruct pulse maximum with method #2 (analytic function) • for each run, get mean value of maximum (resolution ~ 1.2%, ~150 events) • Laser runs : • APD : reconstruct pulse maximum with method #2 • PN : reconstruct pulse maximum with 3rd deg. poly. • For each run, get mean value of APD/PN (resolution ~ 1%, 1000 events) Julien Cogan CERN/EP/CMA

  3. DURING BEAM PERIOD : STEP #1 • Step UP : 18C  19C (04/08/02  05/08/02) • change room temperature ambient & regulation circuit simultaneously • beam on crystal #1230 • fixed gain mode on FPPA • laser intensity too high  SATURATION • At equilibrium (after ~12 h) • scan over 64 crystals (around #1230) • reduce laser intensity ( 30%) • Step DOWN : 19C  18C (05/08/02  06/08/02) • change room temperature ambient & regulation circuit simultaneously • beam on crystal #1142 • At equilibrium (after ~12 h) • scan over 24 crystals (around #1230) Julien Cogan CERN/EP/CMA

  4. DURING BEAM PERIOD : STEP #2 • New scan with reduced laser intensity (30 %) to avoid saturation • Beam on the same crystal during step UP & DOWN • Step UP : 18C  19C (14/08/02  15/08/02) • beam on crystal #1142 • At equilibrium (after ~12 h) • scan over 25 crystals (around #1142) • Step DOWN : 19C  18C (15/08/02  16/08/02) • beam on crystal #1142 • At equilibrium (after ~12 h) • scan over 25 crystals (around #1142) Julien Cogan CERN/EP/CMA

  5. STEPS #1 & 2 : REMARKS • From previous analysis (see M0 meeting 15/10/02 ECAL WEEK) : • fluctuations of the laser pulse width induce an effect on ADP/PN • systematic change of the laser intensity when temperature is changed • not understood fluctuations on APD/PN (crude timing correction attempted) • observed sensitivity to temperature : ~ 3% / C ??? 6h 2h STEP #1 DOWN STEP #2 3% APD/PN 3 % APD/PN PN PN 30% 20% Julien Cogan CERN/EP/CMA

  6. AFTER BEAM PERIOD : STEP #3 • After change of laser lamp & laser tuning • New temperature steps : • try to quantify the temperature effect on laser intensity • temperature sensor installed on laser table • get cleaner data for APD gain -VS- temperature studies • Step UP : 18C  20C • room (29/10/02) • ambient circuit (30/10/02) • regulating circuit (31/10/02) • Step DOWN : 20C  18C • ambient circuit (4/11/02) • regulating circuit (5/11/02) • room (6/11/02) ? 12h STEP #3 UP 10% PN Smaller effect than in steps #1 & 2 !! 33C 1.5C LASER BARACK Julien Cogan CERN/EP/CMA

  7. STEP #3 UP : Regul. @ 20C Temperature on capsules Ambient @ 20C Room @ 20C 2C 1 day APD/PN All crystals normalized 5 % Julien Cogan CERN/EP/CMA

  8. STEP #3 UP : ROOM Temperature on capsules 1/2 day 0.1C Not negligible effect of external temperature ! APD/PN 0.4 % Julien Cogan CERN/EP/CMA

  9. STEP #3 UP : AMBIENT Temperature on capsules 6 h 1C Large dispersion : temperature depends on crystal position ! APD/PN 1.5 % Julien Cogan CERN/EP/CMA

  10. STEP #3 UP : REGULATION (1) Temperature on capsules 6 h 2C At equilibrium : dispersion is very much reduced APD/PN 5 % Julien Cogan CERN/EP/CMA

  11. STEP #3 UP : REGULATION (2) Temperature on capsules ~20mn 2 h 2C 50 % APD/PN 5 % Julien Cogan CERN/EP/CMA

  12. STEP #3 UP : APD GAIN VARIATION @18C @20C APD/PN 96 xtals MEAN = -5.23 % RMS = 0.13 % variation with temperature OBSERVED APD GAIN SENSITIVITY : -2.6 % / C APD/PN(19  -18) APD/PN(18 ) • Note : same analysis on previous steps: • step #1 : -3.2 % /C(RMS = 0.2%) • step #2 : -3.0 % /C(RMS = 0.1%) Julien Cogan CERN/EP/CMA

  13. STEP #3 : REMARKS & CONCLUSION • Much cleaner data than in previous steps • Laser sensitivity to temperature seems reduced • APD gain sensitivity to temperature still a bit higher than expected : • 2.6 % /C instead of 2.4 % /C • PN variation with temperature ? • Time constant characteristic for the APD : • order of ~ 1/2 h • analysis should be refined PN2/PN0 drops of 0.2 % when changing the ambient circuit Julien Cogan CERN/EP/CMA

  14. STEPS 1 & 2 : BEAM STEP #1 XTAL #1142 XTAL #1230 5 % scan scan All crystals normalized 6 h STEP #2 XTAL #1142 XTAL #1142 5 % scan scan All crystals normalized 6 h Julien Cogan CERN/EP/CMA

  15. STEPS 1 & 2 : BEAM - XTAL #1142 2 h STEP #1 DOWN 1.03 3% 1. normalized STEP #2 UP 1.02 4% 0.98 STEP #2 DOWN 1.015 3.5% 0.98 Julien Cogan CERN/EP/CMA

  16. STEPS 1 & 2 : RAD. DAMAGE ? (1) 2 h Beam on XTAL # 1142 APD(1142)/PN Loss du to irradiation APD/PN> (others) 0.8 % STEP #1 DOWN STEP #2 UP No effect ? STEP #2 DOWN Julien Cogan CERN/EP/CMA

  17. STEPS 1 & 2 : RAD. DAMAGE ? (2) 2 h STEP #1 DOWN (Beam on XTAL # 1142) APD(1143)/PN APD/PN> (others) 0.4 % (close to beam) APD(1227)/PN APD/PN> (others) 0.4 % (close to beam) APD(1147)/PN APD/PN> (others) No effect (far from beam) Julien Cogan CERN/EP/CMA

  18. STEPS 1 & 2 : RAD. DAMAGE ? (3) • Evidence for radiation damage on crystal 1142 during step #1 : • observed : 0.8 % decrease of the signal with the laser • implies 0.8 %  1.45 = 1.16 % on the electron signal ? • Observed a drop between the step #1 and step #2 • ? • Radiation damage absent or much smaller during step #2 : • no recovery ? • rates ? : • Counter rate (S5 / 2 min) Step #2 3000 2000 Step #1 Julien Cogan CERN/EP/CMA

  19. STEPS 1 & 2 : SCANS Look at variation of response for scanned crystal at both temperature (18 & 19 C) APD(19  -18) (%) Variation : V = 100  APD(18 ) Step #1 : 25 crystals Step #2 : 23 crystals MEAN = -3.7 % RMS = 0.4 % MEAN = -3.8 % RMS = 0.3 % V(%) V(%) Variation much less than expected (~ 4.3 %) Julien Cogan CERN/EP/CMA

  20. STEPS # 1 & 2 : COMPARAISONS V (%) Comparison between the beam data : Step #1 -VS- step #2 : 9 crystals  poor reproducibility !! Comparison with laser data (step #3) : V (%) V (%) V (%) Step #1 : 24 crystals  poor correlation Step #2 : 23 crystals  better correlation V (%) V (%) Julien Cogan CERN/EP/CMA

  21. THERMAL STEPS : CONCLUSION • Laser data (step #3) : • measure : -2.6%/C on 96 crystals • time constant : order of 1/2 hour • Beam data (step #1 & 2) : • measure : ~-3.8%/C on 38 crystals • time constant : order of 1.5 hour • bad reproducibility of measurement : • still need to look at systematic effect • need to look in more detailed to correlation with laser data Julien Cogan CERN/EP/CMA

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