WACH4 26/11/2002Julien Cogan CERN/EP/CMA-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)

WACH4 26/11/2002Julien 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)

WACH4 26/11/2002Julien 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)

WACH4 26/11/2002Julien 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)

WACH4 26/11/2002Julien 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 ??? 20% PN APD/PN PN APD/PN3% 30% STEP #1 DOWNSTEP #2 6h 2h

WACH4 26/11/2002Julien 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) 10% STEP #3 UP 1.5  C 33  C LASER BARACK PN 12h Smaller effect than in steps #1 & 2 !! ?

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-7- STEP #3 UP : 20  C 20  C 20  C 1 day Temperature on capsules 2C2C APD/PN All crystals normalized 5 %

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-8- STEP #3 UP : ROOM Temperature on capsules APD/PN 1/2 day 0.1  C 0.4 % Not negligible effect of external temperature !

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-9- STEP #3 UP : AMBIENT Temperature on capsules APD/PN 6 h 1C1C 1.5 % Large dispersion : temperature depends on crystal position !

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-10- STEP #3 UP : REGULATION (1) Temperature on capsules APD/PN 6 h 2C2C 5 % At equilibrium : dispersion is very much reduced

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-11- STEP #3 UP : REGULATION (2) Temperature on capsules APD/PN 2 h 2C2C 5 % 50 % ~20mn

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-12- STEP #3 UP : APD GAIN VARIATION MEAN = % RMS = 0.13   C OBSERVED APD GAIN SENSITIVITY : -2.6 % /  C APD/PN 96 xtals variation with temperature Note : same analysis on previous steps: step #1 : -3.2 % /  C (RMS = 0.2%) step #2 : -3.0 % /  C (RMS = 0.1%) APD/PN(18  )  APD/PN(19  -18  )

WACH4 26/11/2002Julien 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

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-14- STEPS 1 & 2 : BEAM XTAL # h XTAL #1142 scan All crystals normalized 5 % STEP #2 STEP #1

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-15- STEPS 1 & 2 : BEAM - XTAL #1142 normalized 3% 4% 3.5% 2 h STEP #1 DOWN STEP #2 UP STEP #2 DOWN

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-16- STEPS 1 & 2 : RAD. DAMAGE ? (1) Beam on XTAL # % STEP #1 DOWN STEP #2 UP STEP #2 DOWN  APD/PN> (others) APD(1142)/PN Loss du to irradiation 2 h No effect ?

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-17- (far from beam) (close to beam) STEPS 1 & 2 : RAD. DAMAGE ? (2)  APD/PN> (others) APD(1143)/PN  APD/PN> (others) APD(1147)/PN 0.4 % 2 h STEP #1 DOWN (Beam on XTAL # 1142) (close to beam) 0.4 % No effect  APD/PN> (others) APD(1227)/PN

WACH4 26/11/2002Julien 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 ? : Step #1 Counter rate (S5 / 2 min) Step #

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-19- STEPS 1 & 2 : SCANS Step #2 : 23 crystalsStep #1 : 25 crystals Look at variation of response for scanned crystal at both temperature (18 & 19  C)  Variation much less than expected (~ 4.3 %) Variation : V = 100  V(%) MEAN = -3.7 % RMS = 0.4 % MEAN = -3.8 % RMS = 0.3 % APD(18  )  APD(19  -18  ) (%)

WACH4 26/11/2002Julien Cogan CERN/EP/CMA-20- STEPS # 1 & 2 : COMPARAISONS Step #1 -VS- step #2 : 9 crystals  poor reproducibility !! Comparison with laser data (step #3) : Step #1 : 24 crystals  poor correlation Step #2 : 23 crystals  better correlation Comparison between the beam data : V (%)

WACH4 26/11/2002Julien 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