April 25, 2012 Tracking CDC/FDC

Meeting Time and Place

Wednesday April 25, 2012 at 11:00am At Jefferson Lab, the meeting will be held in F326

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Hardware Agenda

1. Announcements
2. Collaboration Meeting
3. FDC Update logbook
4. CDC Update
   1. Construction Update planned HVB wiring map
   2. Cosmic Calibration of the Chamber
5. TDR Update

Tracking Software Agenda

1. Announcements.
2. Summary of current work on tracking.
   1. Hit pruning and broken track recovery has been improved
      1. Pruning cut (distance in σ between projection of track and hit) is iteration dependent (currently starts at 30σ and goes down to a minimum value of 3σ)
      2. Single track reconstruction before recent changes
      3. Single track reconstruction after recent changes
   2. Spiral Track Update (Paul)
3. Where we need to focus work (Discussion)?

Hardware Minutes

Participants: Curtis, Naomi, Eugene, Beni, John, Simon, Mark, Lubomir

1. FDC Update
   1. No more oxygen in the FDC: first cell of package #3 was assembled with coated G10, Viton O-rings with vacuum grease applied on the top which resulted (after 5 days flushing) in 75ppm oxygen, almost the same as in the supply gas. All channels were tested with a source. Chamber is much more quite, signals are higher and very uniform along the wires, working HV lower: ~2050V.
   2. One more cell was installed but chamber not tightened. The plan is to put two more cells and then start flushing with gas and testing all four cells together.
   3. Beni found a way to ground the wire frames in the first package in 126 so that the working threshold went down significantly, from 13 to 3.5-4.5V. The trick was to replace the grounding wires with foils.
2. CDC Update
   1. Construction Update
      1. The Rohacell ring has been dryfitted, that was a very nice fit. The chamber is suspended by its support brackets and the flange has been removed from the pipe prior to dry-fitting of the Al ring (upstream plenum inner hub). The cheeseplate is ready to go on when the Al ring is in place, its standoffs are already in place. Holes have been drilled in the endplates for the thermocouples; these have been installed at the upstream end.
      2. Naomi finished a wiring map plan for the CDC (linked to the agenda), mostly 3 rows of straws per board, with the straws with longest wires swapped onto nearer boards to reduce their length resulting in ~50 boards with 1 straw from a 4th row, and estimated mean wire length approximately 4.1in.
   2. Prototype
      1. Following the discussion last week Naomi changed the CDC prototype triggering so that one scintillator signal completely covers the other (not just the leading edge of the other) but the lumps in the drift time spectrum are still there (see pale teal green histogram very close to the end of CDC_prototype_more_on_timing_3).
      2. Lubomir suggested checking the preamp voltage as he found that correcting this reduced the event signal tails.

Software Minutes

Participants: Curtis, Naomi, Eugene, Beni, John, Simon, Mark, Lubomir, Paul

1. Hit pruning during track reconstruction is now iteration dependent rather than all at once, causing the chi-squared to improve significantly in the regions near 20 degrees and 130 degrees
2. In single track, slow pion events at theta = 90, the # of reconstructed track candidates has been significantly reduced. Wire- and time-based reconstruction is still poor, will try to improve track candidate θ reconstruction.