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March 5, 2015 FDC+CDC meeting


  1. Instructions for Bluejeans meeting connection
  2. FDC meeting ID: 290664653
  3. To join via a Web Browser, go to the page [1] https://bluejeans.com/290664653.


  1. Gas issues
  2. CDC update (Mike)
  3. FDC update (Lubomir)
  4. Electronics (Fernando, Cody, Chris, Nick)
  5. Engineering (Dave)
  6. Other


Participants: Curtis, Naomi (CMU) Eugene, Fernando, Dave, Mike, Chris, Nick, Simon, Beni, and Lubomir (JLab).

Gas issues

- CO2 was monitored for two weeks. Two sets of measurements are shown in the above plots. First plot: starting with certified gas (60% CO2) in EEL126 then moving the sensor (without disconnecting from the laptop) to the Hall and sensing first FDC1 for several days and at the end switching the solenoid valve to the CDC. Shown are the atmospheric pressure, sensor results and the ones corrected for the pressure: ~(dleta_p/p)^n, where the power n was chosen, on the first plot, to make the calibration measurements flat (n=2.4). Second plot is the same except n=1.4 which makes the CDC measurements plat. Third and fourth plots represent the second set of measurements, starting with 5 days sensing CDC and then few days FDC1.

- Discussions:generally FDC is off by 4-5% consistent with the time-to-distance results. CDC is off by 8-9-10% while the time-to-distance from the data requires ~6% off (or ~44%). Proposal: to calibrate the sensor with a gas that is closer to the 40% CO2 as measured in the CDC. Need more calibration measurements to be sure the pressure correction is correct. If assume n=1.4 CDC is more stable then the FDC, could be due to the higher flow.

- Gas gain calibrations: using Fe source measurements were done in the EEL126 with the spare package at three different HV (first plot). They will be compared to the results from the Hall with the source put at the downstream side of FDC. Second plot shows some change of the gas gain with the atmospheric pressure. Since the gas properties scale with field/pressure, it goes in the right direction.

CDC update

- CDC was left without alcohol for a week - very small change (~1%) in the drift-time spectrum.

FDC update

- The Chiller came back from the repair and was connected to the FDC, so far works fine.

- One HV channel tripped, took several days to set it back.


- Beni: new f125 firmware on all modules. CDC was read out for 24 hours at 30kHz without crashing.


- Dave: CDC flow sensor connected and operational. FDC chiller shut off also connected and tested.