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Updates on GEMs characterization with APV electronics. K. Gnanvo , N. Liyanage , K . Saenboonruang. outline. Performance of small GEM with Fe55 source and SRS e lectronics Experimental setup Measurement of the Fe 55 spectrum Estimation of the absolute gain

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Updates on gems characterization with apv electronics

Updates on GEMs characterization with APV electronics

K. Gnanvo, N. Liyanage, K. Saenboonruang


outline

  • Performance of small GEM with Fe55 source and SRS electronics

    • Experimental setup

    • Measurement of the Fe 55 spectrum

    • Estimation of the absolute gain

  • Performance the SBS proto I with Sr90 source and SRS electronics

    • Experimental setup

    • Gain uniformity and efficiency

    • Effect of the gas flow rate

  • Updates on the APV25-MPD electronics

    • Progress in the decoding and display software

    • Debugging the daq software and other issues


Setup of the Small GEM chamber with 55Fe

  • Low pass filter used to reduce high frequency noise.

  • The cut off frequency for this low pass filter is 10 MHz.

3T

GEM Chamber

Discriminator

Low

pass

Filter

Fe55

CR-110

Amplifier

66 Ω

470 pF

150 nF

Vin

Vout

Gate/Delay

220 pF

SRS DAQ

Trigger


Study of the noise (rms of the apv25 channels)

  • Typical rmsnoise of a given APV cards from a pedestal run SRS

  • This rms is obtained after common mode correction of the baseline

    • An average of 6-7 adc counts for apv25-SRS

    • ~ 1200 to 1500 ENC

  • a cut at 5 sigma for zero suppression  ~ 6000 e-

APV25-SRS

on GEM readout strips


55Fe spectrum

  • HV = 4 kV on the voltage divider

  • Trigger threshold at 50 mV on GEM foil

  • Distribution of strip cluster max ADC counts  the Fe55 spectrum

Photo-peak

X-strips

Y-strips

Escape peak


55Fe spectrum vs. HV

X-strips

3950 V

4000 V

3850 V

3900 V


Gain of the small triple GEM with 55Fe

  • Gain from the mean ADC value of the photo peak

  • APV gain calibration = 238e- /adcchannel

  • Gain is about twice the gain we obtain from direct measurement

    • SRS electronics gain with external pulse is overestimated

    • strip capacitance and cross talk effect of the GEM readout not taken into account


Performance of the small GEM prototype with 55Fe

  • Good chamber efficiency

  • Strong variation of the X/Y charge sharing with the applied voltage  Gain


Setup of the SBS GEM chamber with 90Sr

  • The test used 90Sr source located above the 1st prototype SBS GEM chamber atdifferent locations to study efficiencies, ADC spectrums, charge sharing and other important characteristics of the chamber by varying the gas flow rates, and directions

  • The threshold of the scintillator was set at 135 mV throughout the test (unless specified by other values)

5

1

3

2

4

Aluminum Plate

D

1-inch Diameter Hole

C

90Sr Source

B

1.5-inch Gap

Active Area

of the scintillator

HV

GEM Chamber

2-cm thick Scintillator


Test of the SBS GEM chamber with 90Sr

Hit distribution

Condition: 1) 200 mL/min < Gas flow rate < 300 mL/min

2) Gas Direction: 1

3) Position: B3

4) HV = 4400 V

3 Sigma Cut

5 Sigma Cut

X-strips

Y-strips


Test of the SBS GEM chamber with 90Sr

Efficiency Calculation

  • Good events mean there are both hits in X and Y directions

  • The equation to calculate the efficiency is

    where NG: Number of good events

    NT: Number of triggers

    RT: Trigger rate with the source (12 Hz)

    RGB: Rate of good events without source (20 % or 0.24 Hz)

    RB: Trigger rate without the source (1 Hz)


Test of the SBS GEM chamber with 90Sr

Efficiency vs HV

Condition: 1) 200 mL/min < Gas flow rate < 300 mL/min

2) Gas Direction: 1

3) 5 sigma cut


Test of the SBS GEM chamber with 90Sr


Test of the SBS GEM chamber with 90Sr


Test of the SBS GEM chamber with 90Sr

Average ADC in X direction

Condition: 1) Gas flow rate = 290 mL/min

2) Gas Direction: 2

3) 5 sigma cut


Test of the SBS GEM chamber with 90Sr

Charge Ratio (X/Y) vs HV

Condition: 1) 200 mL/min < Gas flow rate < 300 mL/min

2) Gas Direction: 1

3) 5 sigma cut


Test of the SBS GEM chamber with 90Sr



New APV25 FE with Panasonic connectors for SBS backtracker GEMs

  • Paolo Musico’s group (INFN Italy) is working on a new version of the APV25 FE cards with Panasonic connectors and new backplanesfor the new SBS backtracker GEM


Design of GEMsew backplanes for SBS back tracker GEMs



APV25 MPD and SRS system GEMs

  • We suspect an overestimation of the gain

    • Gain from external source is about 2 × the gain with calibration pulse

    • The estimate GEM gain from the APV-SRS signal size is about twice the expected gain

  • We need to re-evaluate the amount of injected charges

    • Try to access the effect of strip capacitances and cross talk ...


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