[Solid_gem] minutes of October GEM monthly meeting

[Jianbei Liu]

Hi All,

Minutes from yesterday's GEM meeting have been attached to the agenda and copied below.

https://hep.ustc.edu.cn/indico/conferenceDisplay.py?confId=7

GEM test with CASAGEM electronics at THU  (Zhigang)
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- the small GEM prototype was tested with 2D readout using 4 CASAGEM modules. The CASAGEM  system worked very well.
  * test results using Fe55:  energy resolution ~28% (FWHM),  spatial resolution ~200um (preliminary)
- frames and gas container all made ready for the large GEM prototype: , readout PCB being redesigned. 
+ to do
  * precise analysis of spatial resolution
  * produce more CASAGEMs aiming at 192 channels in total 
  * assembling of the large GEM prototype 
   * continue with the small GEM test


Preliminary test beam results of EIC-SoLID GEM prototype by UVa (Kondo)  
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- design of the GEM prototype and preparation and setup for the test were presented (see the slides for details)
- HV and position scans performed
- preliminary results show all sectors of the prototype chamber functioning pretty well. There are some noisy channels indicated by the high spikes in the pedestal distributions. the pattern of a low pedestal channel alternating with a high one is understood and related to the variations in size (determining the capacitance) of the readout strips.
+ to do
  * fully analyse the data, perform more studies (gain, spatial resolution, noise …)
  * implement readout mapping 
  * improve GEM foil stretching method and optimise the 2d readout

GEM status at USTC  (Yi) 
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-  changed the gas mixer. gas condition stays stable now and the significant time variation observed before on gas gain is gone.
-  a GEM cleaning system is fully set up comprising an ultra-sonic bath, a water filter and an oven. Shorted sectors of the 30*30cm^2 GEM chamber were recovered after being cleaned with the system demonstrating the functionality of the cleaning system.
+ to do
  * test the cleaned GEM chamber
  * prepare for building another GEM prototype chamber

 GEM activities at LZU (Xiaodong)
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- showed simulation results (electric field distribution, gas gain as a function of various variables ... )of a single-layer GEM and a regular triple GEM.
- tested a single layer GEM chamber with Fe55. studied gas gain and energy resolution in different HV configurations (e.g. various GEM voltages, drift and induction electric field) to find the optimal operation point.  A energy resolution of ~18% was obtained at the optimal operation point.
- assembled and tested a triple GEM chamber. Measured energy resolution and gas gain as a function of drift electric filed strength and GEM voltage. 
+ to do
   * continue with the GEM tests

Status of the GEM readout system debugging at CIAE (Siyu)
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-  things tried: changed power supply,  tested with both NIM and TTL trigger signal, updated MPD firmware, changed config file.
-  problems still there: digital header much higher than ticks?, trigger lost
-  an INFN bus was purchased and is being shipped to China. will arrive at CIAE next week.
+ to do  
  * continue debugging the readout system, particularly with the INFN bus when it arrives.

Jianbei