thgem tests @ cern
DESCRIPTION
THGEM TESTS @ CERN. September 2008 Freiburg Team Torino Team Trieste Team. Outline:. Setup description (prototypes, electronics, sources); “Small chamber” and “medium chamber”: gain characterization; Electronics tests with MAD4 and CMAD; Conclusions. Used setup (1/2). - PowerPoint PPT PresentationTRANSCRIPT
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THGEM TESTS @ CERN
September 2008Freiburg TeamTorino TeamTrieste Team
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Outline:
1. Setup description (prototypes, electronics, sources);
2. “Small chamber” and “medium chamber”: gain characterization;
3. Electronics tests with MAD4 and CMAD;
4. Conclusions.
2Elena Rocco
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Used setup (1/2)
Chamber name
THGEM name
Structure type
Diam (mm)
Pitch (mm)
Thick (mm)
Rim (m)
Drift_gap (mm)
Transfer gap(mm)
Induction gap (mm)
Small C7 double 0.4 0.8 0.4 10 4.5 1.6 1.6
Medium R3 double 0.2 0.5 0.2 10 10 2.5 2.5
Small 1 C7 triple 0.4 0.8 0.4 10 5 1.6 1.6
Geometrical parameters and labels of the THGEM prototypes used
•2 55Fe sources available with 2 different intensities;•3 THGEM prototypes (see table below);•Bottle of gas premixed: Ar/CO2 70/30 %; •Cooling for the electronics provided;•Electronics in loco and event builder (pccofe03) available for running the acquisition independently from the main COMPASS DAQ.
Medium chamber
3Elena Rocco
Front End and cooling
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Used setup: electrical schemefor the small chamber (2/2)
DRIFT
TOP 1
BOTTOM 1
TOP 2
BOTTOM 2
anode
drift
THGEM 1
THGEM 2
Einduction
Etransfer
Edrift
CONFIGURATION INSIDE THE CHAMBER
POWER SUPPLY
POWER SUPPLY
POWER SUPPLY
R=500 M
R=500 M
R=500 M
100 pF
100 pF
100 pF
R=6 G
R=8 G
R=5.5 G
R=2.5 G
For the medium chamber the resistors in the electrical scheme are different values due to the different amplitude (charge) of the signal.For the triple THGEM is completely different
4Elena Rocco
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Gain Characterization for the small chamber
13761378
13801382
13841386
1388
1390
1392
80828486889092949698
100102104106108110
1060
1065
1070
1075
1080
Gai
n
V2 (V)
V1 (V)
Signal from the anode
•Weaker Iron source has been used for this gain characterization);•Rate few Hz;•Readout from the anode (CREMAT pre+amplifier)
Drift field kept fixed: Edrift1.6 kV/cm
5Elena Rocco
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Gain Characterization for the medium chamber
6406606807007207407607808008208408608809009209409609801000102010
100
Gain
Vi (V) with i=1,2
V1 fixed @ 620V and V2 varying V1 fixed @ 820V and V2 varying V1 fixed @ 840V and V2 varying V1 fixed @ 890V and V2 varying V1 fixed @ 900V and V2 varying V1 fixed @ 920V and V2 varying V2 fixed @ 860V and V1 varying
•Performing this gain characterization the transfer field was changing slightly by applying different voltage to THGEM 2;•55 Fe source used (the weaker one);•Rate 50 Hz;•Readout from the anode (CREMAT pre+amplifier)
Drift field kept fixed: Edrift=0.22 kV/cm
MEDIUM CHAMBERCoincidences: BOTTOM2 , PM1, PM2 6Elena Rocco
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Triple THGEM signal
Reading out form the anode Gain estimation using the CREMAT amplifier
Rate 145 Hz
7Elena Rocco
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Electronics Tests (1/2)
8Elena Rocco
Concerning the CMAD :
•The pedestal was optimized (650 digit), but not the noise.
Concerning the MAD4 :
•A common threshold above the noise has been put (40 digits).Remind: the gain in the MAD4 is fixed, the digit range is smaller and the granularity is double respect the CMAD (0.9 mV/digit(?))
The gain in the chip CMAD can be programmed; The gain range is from 4.8 mV/fC to 0.4 mV/fC in discrete steps ;The granularity is 0.45 mV/digit;The range of the threshold is divided in 1024 digit, but we are using just half: from 650 digit (a little bit above the noise level) to 0 digit (the higher threshold attainable).
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Electronics Tests (2/2)
9Elena Rocco
1. The tuning of the electronics is not perfect because there’s some noise coming from some MAD chip.
2. Later on, after a fine tuning of the electronics, the scan in gain and in threshold have been performed.
3. A check in amplitude values of the signal has been done between the measured value and the calculated value from the whole electronics chain.
Time peak acquired from our DAQ
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Conclusions (quite preliminary):The prototypes can provide stable and reproducible signals, from the amplitude point of view; The electronics chain is ready to be used and is suitable for reading out the signal from the detectors with the THGEMs;The loading files are ready for changing the thresholds in the whole electronics (MAD and DREISAM) and for further noise studies.
For the near future:Geometry is still to be chosen (further characterizations should be done); tests with different gases;Run using the cosmic rays could be taken because the setup is ready (medium chamber). 10Elena Rocco