GEM Fall Studies
From Hall A Wiki
Studies for GEM "pad" readout
- Initial studies (Oct 28, 2011)
- General Setup: 90Sr source with scintillator below the GEM as the trigger. Threshold on the scintillator is 40mV. The GEM is a "pad" readout with one preamp. The gas for GEM is Ar/CO2 at 75/25 mixture.
- DAQ is using the flash ADC with GEM in Chan 1 and Scintillator in Chan 2. Flash ADC is sampling at 250Mhz so sample every 4nsec.
| Run Number | GEM HV | Comment |
|---|---|---|
| 1025 | 3.4kV | Low voltage on preamp = 3.5V |
| 1026 | 3.52 | Scint signal was missing. Forgot to plug it back in after looking at scope. |
| 1027 | 3.52 | Event rate = 56/sec |
| 1028 | 3.52 | No source. Event rate = 10.4 /sec. So maximum GEM efficiency is 81.4%. |
| 1029 | 3.52 | |
| 1030 | 3.56 | |
| 1031 | 3.47 | |
| 1032 | 3.47 | Low voltage on preamp = 5.0V |
| 1033 | 3.53 |
- Plots of flash ADC value versus the sample number for the full time range and smaller time range. The blue line is a fit with a Landau function. The red line is a "constant fraction discriminator" line which is basically trying to simulate a CFD by adding the inverse of the blue curve with a time offset and different scale. Needs to be optimized.
- Time resolution plot with scal of sample ( 4ns/sample). The time is determined by the zero crossing of the "CFD".
- Efficiency plot for a cut of 50 ADC channels. Expect a maximum efficiency of 81.4% from trigger. The 2d plots are the "CFD" zero crossing versus the height of the ADC.
