THGEM TESTS @ CERN

September 2008Freiburg TeamTorino TeamTrieste Team

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

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

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Front End and cooling

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

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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

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Gain Characterization for the medium chamber

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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

Triple THGEM signal

Reading out form the anode Gain estimation using the CREMAT amplifier

Rate 145 Hz

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Electronics Tests (1/2)

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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).

Electronics Tests (2/2)

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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

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