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August 6, 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. CDC update (Mike, Simon, Beni)
    • Test1: current setup
    • Test2: + grounding cable btw. ring and spade connector (50 ohm)
    • Test3: same as Test2 but replace 50 Ohm with short
    • Test4: + grounding cable btw. ring and standoff
    • Test5: like test4 with additional cable to spade connector (0 ohm)
    • Test8: like test 3 but connect standoff between to neighbouring cards
    • Test9: like test 4 but connect standoff between to neighbouring cards
Connector Test1 width Test2 width Test3 width Test4/5 width Test8/9 width
F2 16.9 17.0 17.0 17.6 16.3
F3 15.6 15.7 15.7 15.6 15.6
F7 15.5 15.6 15.6 15.7 15.8
F8 15.6 15.6 15.6 15.6 15.7
  1. FDC update (Lubomir, Luke)
  2. Electronics (Fernando, Chris, Nick)
  3. Engineering
  4. Other


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

CDC update

- Simon studied the effect of the wire offset on the drift time using Garfield - see the logbook entry above. An offset of 1mm will make a factor of two difference in the drift time from the two extreme distances. In a good approximation the time-to-distance relation is symmetric w.r.t. wire position.

- Discussion about what might be the cause for such offsets: sagging of the wires not likely, possibly deformation of the tubes. Naomi described the gluing process - the straws were strapped during curing then released on the next day. All the tubes were checked for flatness. Everybody agrees, we need more cosmic data to study the z,phi dependence of the deformations. Simon will look also in the beam data.

- One CDC wire (on D6 connector) broke. According to Beni we lost HV on that wire at 4:26am on July 28th, that could be the time it broke. Naomi: about 10 wires broke in the first several weeks after their installation and were replaced.

- Nick: separated the broken wire from the HV. 10 channels from HV sector 5 tripped recently.

- Beni and Nick investigated different grounding configurations - see table above. Connecting the standoffs between two cards reduced the noise by about 4%. The hope is that connecting more cards will further reduce the noise. Fernando: need to consider the resolution/efficiency improvement since this is a lot of work.

FDC update

- Lubomir showed results with microscopic, MC type, Garfield simulations of the avalanche. Last two plots show distributions of the avalanche electrons - as function of distance to the wire (on average very close to the wire), and position along the wire (only ~6 micron spread). The asymmetry in the signals on the two cathodes can be predicted by the microscopic simulations at least qualitatively. The results depend on the exact electronics response function and the ion contribution. The asymmetry in the cathode signals comes from the asymmetry in the weighting field at the two sides of the wire, demonstrated in the other plots above.


- Finally we have about 50/50 gas mixture in both detectors - see the CO2 sensor results attached above. The measurements were done by switching between FDC (lower CO2) and CDC (higher CO2 percentage).