1. Updates on GEMs characterization with APV electronics K. Gnanvo, N. Liyanage, K. Saenboonruang

2. 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 outline

3. Setup of the Small GEM chamber with 55 Fe Fe55 GEM Chamber SRS DAQ 3T 470 pF CR-110 Amplifier 150 nF Low pass Filter Discriminat or Gate/Delay Trigger V in V out 66 Ω 220 pF Low pass filter used to reduce high frequency noise. The cut off frequency for this low pass filter is 10 MHz.

4. Study of the noise (rms of the apv25 channels) APV25-SRS on GEM readout strips Typical rms noise 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-

5. 55 Fe spectrum X-stripsY-strips Photo-peak Escape peak 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

6. 55 Fe spectrum vs. HV 4000 V X-strips 3950 V 3900 V 3850 V

7. Gain of the small triple GEM with 55 Fe Gain from the mean ADC value of the photo peak APV gain calibration = 238e- /adc channel 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

8. Performance of the small GEM prototype with 55 Fe Good chamber efficiency Strong variation of the X/Y charge sharing with the applied voltage  Gain

9. Setup of the SBS GEM chamber with 90 Sr The test used 90 Sr source located above the 1 st prototype SBS GEM chamber at different 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) GEM Chamber 2-cm thick Scintillator 90 Sr Source Active Area of the scintillator 1-inch Diameter Hole Aluminum Plate 1.5-inch Gap HV B C D 1 2 3 4 5

10. Test of the SBS GEM chamber with 90 Sr Hit distribution Condition: 1) 200 mL/min < Gas flow rate < 300 mL/min 2) Gas Direction: 1 3) Position: B3 4) HV = 4400 V 5 Sigma Cut3 Sigma Cut X-strips Y-strips

11. Test of the SBS GEM chamber with 90 Sr Efficiency Calculation Good events mean there are both hits in X and Y directions The equation to calculate the efficiency is where N G : Number of good events N T : Number of triggers R T : Trigger rate with the source (12 Hz) R GB :Rate of good events without source (20 % or 0.24 Hz) R B : Trigger rate without the source (1 Hz)

12. Test of the SBS GEM chamber with 90 Sr Efficiency vs HV Condition: 1) 200 mL/min < Gas flow rate < 300 mL/min 2) Gas Direction: 1 3) 5 sigma cut

13. Test of the SBS GEM chamber with 90 Sr

15. Average ADC in X direction Condition: 1) Gas flow rate = 290 mL/min 2) Gas Direction: 2 3) 5 sigma cut

16. 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 16 Test of the SBS GEM chamber with 90 Sr

17. 17 Test of the SBS GEM chamber with 90 Sr

18. Updates on the APV25-MPD

19. 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 New APV25 FE with Panasonic connectors for SBS backtracker GEMs

20. Design of ew backplanes for SBS back tracker GEMs

21. Backup slides

22. APV25 MPD and SRS system 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...