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January 22, 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. Collaboration meeting agenda
  2. Gas puzzle
  3. CDC update (Mike)
  4. FDC update
    • Gain calibration (Vlad)
  5. Electronics (Fernando, Cody)
    • HVB refurbishment (Nick, Chris)
  6. Engineering (Dave)
  7. Other


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

Collaboration meeting agenda

- In addition to the allocated talks, Vlad needs 10 min for "FDC gain calibration". Eugene: this is a tracking session and should be devoted to tracking and calibrations, f125 stuff can go to the electronics, but there's no electronics sessions? To be discussed next time again.

Gas puzzle

- Lubomir investigated the effects of the alcohol in the gas using Garfield. Experimental results (first plot) from the FTD detector at HERA show increase of the drift velocity with the increase of the ethanol in their Ar/propane mixture. Garfield simulations (next two plots) describe this results well enough. Contrary, adding 1-propanol in our gas mixtures of Ar/CO2 makes the gas slower, and surprisingly increases the gain significantly - 70% if adding just 1% (absolute) alcohol. Thus, a mixture of 54/45/1 Ar/CO2/propanol explains (next two plots) both, the CDC time-to-distance and the increase by a factor of ~4 of the gain compared to the 50/50 mixture. It's difficult to estimate the propanol percentage during the last run. If using the vapor pressures and assuming equilibrium, it must be 0.2-0.5% ranging due to the temperature and pressure variations in the alcohol bubbler. If roughly estimate the alcohol consumptions it must be closer to 1%.

- At least the CO2 content will be known soon. We have received a CO2 sensor (0-100% range) that is based on UV light absorption by the CO2 molecule. Needs calibration, will use a certified Ar/CO2 bottle ~40/60, and pure CO2.

- Naomi showed her latest results (linked above) from CMU using the prototype. She used 50/50 55/45 and 60/40 Ar/CO2 gas mixtures. There's an big increase in the gain between 55/45 and 60/40 but not that much between 50/50 and 55/45, If compared with the JLab results with no filed the mixture must be between 55/45 and 60/40 if there's no alcohol. Also the JLab results correspond to tracks from cosmics. Naomi will do also measurements with the JLab electronics.

FDC update

- Vlad showed some studies of the systematics of the gain calibration procedure, comparing results using all the hits, and only those that are part of reconstructed tracks for the fourth package. The are statistically very similar. The channels with correction coefficients >1 (assumed to be "bad") show some differences (up to 50%) when using the two methods.


- All CDC HVBs will be installed by Monday and the-routing of the HV cables will be finished in the first week of February. Fernando: some of the pins of the pre-amp connector on the HVbs were bent; brackets are installed that prevent removing the pre-amps. To replace it you need to disconnect the whole HVB.

- Cody has made changes in the firmware related to the block transfer (larger FIFO in the front-end chip) and trigger rate issues. Will test all these changes at once.


- Dave has prepared the box for the FDC chiller shut off to be connected when the chiller is back. The PLC software is ready, as well.

- Dave is going to install a thermo-couple in the alcohol refrigerator, connected to the PLC for monitoring the temperature.