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September 17, 2015 Drift Chamber meeting


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


  1. Collaboration meeting agenda
  2. CDC update
  3. FDC update
    • studies with 90Sr and 55Fe on spare package: [2], [3]
  4. Electronics
  5. Engineering
    • MFC issues [4]
  6. Other


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

Collaboration meeting

- Sergey was included in the tracking/drift chamber session with a talk about the Transition Radiation Detector.

CDC update

- Simon showed new plots on the CDC tube deformation (elog linked). In addition to the last meeting results, now he has plots for positive/negative delta(phi) and most interestingly their sum and difference. The sum looks very uniform indicating that the tube radius is OK and also that the wires are at the right positions. This is not the case for the difference, which means the wires are not in the center of the tube. We conclude the tubes are deformed resulting in up to 2mm offset of the tube center w.r.t. the wire.

- Mike is working on the same studies but using cosmics. While Simon's beam result see the asymmetry in phi direction, the cosmic result would indicate asymmetry in horizontal direction. It is important to study also the z-dependence.

FDC update

- Cody and Sergey were able to run the new firmware with 1000-samples window on the right side of the tagger crate with the spare package. First plot above shows the signals (from bottom to top) from the first chamber wires, first chamber cathodes, and second chamber cathodes, when using 90Sr source; a second cell wire used for triggering. The max drift time (>8usec) looks bigger than expected from Garfield ~5 usec. This indicates different gas mixture (nominally 90/10 Ar/CO2) or weaker fields. Second plot shows a result with 55Fe source: total charge on x vs width of the signal in time (on y), the later estimated by the (total charge)/(max amplitude). The widening of the signal is explained by the diffusion at big drift distances which effect is amplified by the increased drift time. Nevertheless, when projecting on the x-axis one can clearly see the Ar peak and the escape peak (the structure at smaller charges).


- There are two independent problems with the FDC MFCs in the hall as explained in the log entry above. First related to the reading of the MFCs by the PLC as explained by Dave: the PLC sends reading requests for each MFC channel separately, but the data comes from a different channel. Dave fixed this issue. The other problem is that the MFC of the first package stops regulating the flow set for 200ccpm when the input pressure goes below 10 psi. According to Beni, the MFCs have been calibrated for 500 ccpm at 10 psi and thsi should never happen.


- No meeting next week, all the rooms occupied by EIC activities.

- Dave: Tina Mann, who worked very successfully on the FDC (especially cathode) production is leaving JLab soon.