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April 16, 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 talks (meeting page)
  2. Gas puzzle
  3. CDC update (Beni, Mike)
  4. FDC update (Lubomir)
  5. Electronics (Fernando, Cody, Chris, Nick)
  6. Engineering
  7. Other


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

Collaboration meeting talks

- After some discussions we decided to have the following talks: Tracking (Simon), CDC update (Mike), FDC update (Lubomir), TR studies with spare package (Lubomir) 10min., f125 Update (Cody) 10 min. Naomi will come with an agenda for the collaboration meeting on the next DC meeting.

Gas puzzle

- Latest results from the CO2 sensor shown above: first plot using pressure correction that works for the CDC, second plot pressure correction that makes the certified gas measurements flat. Conclusion: the C02 percentage in the CDC has stabilized at about 52-53%. Curtis: we need to do measurements and then decide if we want to change the gas mixture. At some point we need to add also alcohol to the gas.

- Fernando: how stable the CO2 percentage should be. The way it works: one should correct for/calibrate the gas as often as possible. Naomi has simulated different gas mixtures. Also, one should correct for the pressure dependence - 1% pressure change results in 7% change of the amplitude.

CDC update

- Mike is working on a code for the CDC alignment using Millepede package. This package has been successfully used in many experiments for tracking alignment including the big LHC experiments.

FDC update

- Now using tracking through all the packages Lubomir studied the old problem: the deviation of the cathode-reconstructed from the nominal wire position exhibits an interference pattern as function of x-coordinate (perpendicular to the wires) with deviations up to +/-200 microns. The question is whether the deviations are coming from the wire position offsets or somehow from the cathode reconstruction. For that we use a third point: the expected hit position from a track reconstructed from the outer packages. For comparison, in the above three plots we use the same events and hits that are coming from the best tracks. The plots show the following mean deviations as function of x: cathode reconstructed - nominal wire position (first plot), cathode reconstructed - expected hit position (second), wire reconstructed - expected hit position (third plot); all plots fitted with sine function plus linear term. One can see similar amplitude and frequency for the first two plots, while the last one is almost linear. It means that most likely the deviations are coming from the cathode reconstruction. However, the statistics is low and one could hardly expect much more from this spring run. Therefore the plan is to scan the spare package with a source.


- Fernando: the HV filter boxes have been installed and the noise on the CDC was reduced dramatically down to ~5mV! See the above a link to the GlueX document for scope pictures and explanations. Fernando explained that the noise on the FDC is much lower because the HV is applied at the other end of the wire. Still there was some noise on the cards that were close to the HV cables, that is expected also to go down.