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Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
Electron detectors for HAPPEX2 and He
•Installation in HRS
•Linearity tests
4
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
Detectors
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
Installation
Installation procedure to be tested next week in the Hall
Coordinate with installation of scanners
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
Linearity and Asymmetry
- Output signal of the PMT :
- Asymmetry measured :
The nonlinear term is proportional to the signal amplitude.
- HAPPEX requirement :
2 2
22 2
(1 )
R L R R L Lmeasured
R L
measured actual
S S L L L LA
S S L L
A A L
2S L L
0.02L
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
Mode of operation of the tube
1. Integrating mode :
- High beam intensity (80 – 100 mA) - Rate in HRS t = 50 MHz in the whole detector- Low gain region- Continuous signal less than 6 A to match ADC range
2. Pulse mode :
- Background study and Q2 measurement- Low beam intensity (factor 200 less counting rate to fire VDCs)- Rate in HRS t = 10 KHz/cm2- High gain region- pulse signal of a few mA
need large dynamic range and good linearity capability
33 ms
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
PULSE mode linearity setup
Method : -HV Blue LED (430 nm)
Remote Filter wheels
8854 BURLE PMT
Pulse generator
Att dB Att dB
-2 dB
ADC
( )( )
( )F
A
S LG L
S L
0
0
( ) ( )
( )
G L G LG
G G L
PedS(La)S(Lf)
Deviation from linearity :
1
(1 )AF
GL
L GL
Normalization (1st order) :
Light flux PMT response
La Lf
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
PULSE mode linearity
- Non linearity at high gain due to saturation in latter dynodes - operating range is in a good linearity region
Resistive base Active base
Ne- Ne-
L
L
250 250
2% 2%
Operating range
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
Linearity in continuous mode setup
Micro Amperemetre
DC voltage
Shutter 1Shutter 2
-HV
Plans to implement this method online for the HAPPEX-2 run
Method :
Use of additivity
1 2
1 2
( )1
( ) ( )
S L LG
G S L S L
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
Linearity in continuous mode
Results for average continuous currentIs the pulse structure still relevant ? Evaluation of the real output current is done with a duty factor of 2 or 3
Resistive base Active base
ADC range
2%
L L
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
Gain drift
Measurement of Drift in gain with a pulse signal and a loadof continuous light background of 1, 5, 15 A
Load ON Load OFF
Gain do depends on output current but timescale very long.no systematics from rate-gain correlation at 30 Hz
Antonin Vacheret DAPNIA/SPhN, CEA Saclay. HAPPEX II Jlab Hall A
conclusion
- Complete tests of linearity for the BURLE 8854 + base
- Resistive base : H gain G = [1E6-3E6] output = [2-8] mA L gain G = [5E3-1E4] output = [10-20] A + filters (0.5,0.2,0.1)
- Active base : H gain G = [1E6-1E7] output = [2-20] mA L gain G = [1E4-2E4] output = [20-40] A + filter (0.1)
