wach4 26/11/2002julien cogan cern/ep/cma-1- thermal steps analysis goals & means : –apply a...

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)


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)


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)


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


• Step DOWN : 19C 18C (15/08/02 16/08/02) – beam on crystal #1142



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


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 !!

?


STEP #3 UP :

Room @ 20C

Ambient @ 20C

Regul. @ 20C

1 day

Temperature on capsules

2C

APD/PN

All crystals normalized5 %


STEP #3 UP : ROOMTemperature on capsules

APD/PN

1/2 day

0.1C

0.4 %

Not negligible effect of external temperature !


STEP #3 UP : AMBIENTTemperature on capsules

APD/PN

6 h

1C

1.5 %

Large dispersion : temperature depends on crystal position !


STEP #3 UP : REGULATION (1)Temperature on capsules

APD/PN

6 h 2C

5 %

At equilibrium : dispersion is very much reduced


STEP #3 UP : REGULATION (2)Temperature on capsules

APD/PN

2 h2C

5 %

50 %

~20mn


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)


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


STEPS 1 & 2 : BEAM

XTAL #1230

6 h

6 h

XTAL #1142

XTAL #1142XTAL #1142

scan scan

scan

scan

All crystals normalized

All crystals normalized

5 %

5 %

STEP #2

STEP #1


STEPS 1 & 2 : BEAM - XTAL #1142

normalized

3%

4%

3.5%

2 h1.03

1.02

1.015

STEP #1 DOWN

STEP #2 UP

STEP #2 DOWN

1.

0.98

0.98


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 ?


(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


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


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) (%)


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 (%)


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

wach4 26/11/2002julien cogan cern/ep/cma-1- thermal steps analysis goals & means : –apply a...

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