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WACH4 26/11/2002 Julien 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 26/11/2002 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)
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-3-
DURING BEAM PERIOD : STEP #1• Step UP : 18C 19C (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 : 19C 18C (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 26/11/2002 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 : 18C 19C (14/08/02 15/08/02) – beam on crystal #1142
• At equilibrium (after ~12 h)– scan over 25 crystals (around #1142)
• Step DOWN : 19C 18C (15/08/02 16/08/02) – beam on crystal #1142
• At equilibrium (after ~12 h)– scan over 25 crystals (around #1142)
WACH4 26/11/2002 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 ???
20%PN
APD/PN
PN
APD/PN3% 3 %
30%
STEP #1 DOWN STEP #26h2h
WACH4 26/11/2002 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 : 18C 20C– room (29/10/02)
– ambient circuit (30/10/02)
– regulating circuit (31/10/02)
• Step DOWN : 20C 18C– ambient circuit (4/11/02)
– regulating circuit (5/11/02)
– room (6/11/02)
10%
STEP #3 UP
1.5C
33C
LASER BARACK
PN
12h
Smaller effect than in steps #1 & 2 !!
?
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-7-
STEP #3 UP :
Room @ 20C
Ambient @ 20C
Regul. @ 20C
1 day
Temperature on capsules
2C
APD/PN
All crystals normalized5 %
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-8-
STEP #3 UP : ROOMTemperature on capsules
APD/PN
1/2 day
0.1C
0.4 %
Not negligible effect of external temperature !
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-9-
STEP #3 UP : AMBIENTTemperature on capsules
APD/PN
6 h
1C
1.5 %
Large dispersion : temperature depends on crystal position !
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-10-
STEP #3 UP : REGULATION (1)Temperature on capsules
APD/PN
6 h 2C
5 %
At equilibrium : dispersion is very much reduced
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-11-
STEP #3 UP : REGULATION (2)Temperature on capsules
APD/PN
2 h2C
5 %
50 %
~20mn
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-12-
STEP #3 UP : APD GAIN VARIATION
MEAN = -5.23 %
RMS = 0.13 %
@18C @20C
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 26/11/2002 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
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-14-
STEPS 1 & 2 : BEAM
XTAL #1230
6 h
6 h
XTAL #1142
XTAL #1142XTAL #1142
scanscan
scan
scan
All crystals normalized
All crystals normalized
5 %
5 %
STEP #2
STEP #1
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-15-
STEPS 1 & 2 : BEAM - XTAL #1142
normalized
3%
4%
3.5%
2 h
1.03
1.02
1.015
STEP #1 DOWN
STEP #2 UP
STEP #2 DOWN
1.
0.98
0.98
WACH4 26/11/2002 Julien Cogan CERN/EP/CMA-16-
STEPS 1 & 2 : RAD. DAMAGE ? (1) Beam on XTAL # 1142
0.8 %
STEP #1 DOWN
STEP #2 UP
STEP #2 DOWN
APD/PN> (others)APD(1142)/PN Loss du to
irradiation2 h
No effect ?
WACH4 26/11/2002 Julien 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 26/11/2002 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 ? :
Step #1
Counter rate (S5 / 2 min)
Step #23000
2000
WACH4 26/11/2002 Julien 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(%) V(%)
MEAN = -3.7 %
RMS = 0.4 %
MEAN = -3.8 %
RMS = 0.3 %
APD(18 )
APD(19 -18)(%)
WACH4 26/11/2002 Julien 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 (%)
V (%)
V (%)
V (%)
V (%)
V (%)
WACH4 26/11/2002 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