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July 23, 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) File:MStaibStrawDeform.pdf
  2. FDC update (Lubomir, Luke)
  3. Electronics (Fernando, Chris, Nick)
  4. Engineering
  5. Other


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

CDC update

- Beni found the CO2 MFC for the CDC was not working. As a result there was only Ar in the CDC, explaining the max HV of 1kV. The MFC will be sent for fixing and two new MFC will be ordered. Scot is working on that but the time frame is not clear yet. In the mean time we decided to connect the CDC and FDC mixing tanks together, and fill both with the FDC MFCs set to 50/50 Ar/CO2 gas mixture.

- Mike showed more plots demonstrating the azimuthal asymmetry in the drift times for one "bad" straw. The time-to-distance is a little different in different directions. The main difference is in the range and, if time is converted into distance, the wire appears to be shifted by ~1mm from the middle in horizontal direction. Beni suggested to divide the tube into (at least three) parts along z to see if this is a real offset of the wire.

FDC update

- Lubomir showed latest cathode resolution results: now we have reached the design resolution of 200 microns. The problem was in the centroid calculations - fitting the signals improves the resolution significantly. The resolution extracted from the wire position improved from 150 to 80 microns, while the directly measured resolution using tracking improved from 250 to 180-200 microns (first plot). There is still systematics in the residuals as function of the distance to the middle of the strips. For the wire-estimated resolution (2nd and 3rd plot) it depends on the wire position (as expected) and varies as sine function with an amplitude of up to 130 microns. For the tracking-estimated resolution (last two plots) this amplitude is 4 times smaller, as expected. The problem is that in both cases there's a left-right asymmetry w.r.t. distance to strip middle - a slope of ~100 microns per strip width. One certainly can correct for this and further improve the resolution.

- Luke showed more results with 5FFe source (linked above), now varying also the field HV. One can see that the distance between the peaks in direction perpendicular to the wire plane increases for smaller charges - no explanation at all.

- FDC is at almost the nominal HV, 2150V. For some of the channels it took a week to condition them after the power outage.


- Beni looked at the FDC noise - it's systematically smaller than the noise in the CDC. Beni wants to try again to improve the grounding by connecting the grounds on the HV board together with a thick cable. Will discuss this with Fernando.