GlueX Start Counter Meeting, June 27, 2013
GlueX Start Counter Meeting
Thursday, June 27, 2013
10 am EDT
JLab: CEBAF Center F326/327
- Review minutes from previous meeting
- Construction Status
- New counters from Eljen/McNeal
- Readiness Review: pre-pre-planning discussion
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Talks can be deposited in the directory
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- FIU: Eric Pooser
- JLab: Chuck Hutton, Mark Ito (chair), Beni Zihlmann
Eric described the five new counters from Eljen/McNeal. He has tested all five. Each measurement took about a day. See his slides for details. Some of his points:
- The shipping container that the counters arrived in is much more robust than the one used by McNeal in the past. The container came originally from Eljen.
- On balance the new counters look much better than any of the samples we have received before.
- Some of the counters has some light buffing scratches on some surfaces.
- The counters arrived with different protective light-tack plastic film than those applied at Eljen. The reason for switching the film is not known.
- The bars had some visible inhomogeneities or ripples not seen in straight bars ass Eljen.
- Comparing the laser scattering images from batch 3 (new ones) versus batch 2, there is much less light escaping the counter, especially in the bend region.
- Time resolution for each bar was measured. The resolution is much better than those seen in previous batches, in the range from about 270 to 370 ps, with the worst resolution coming from the bend region. The improvement at the nose is from about 370 ps with previous counters to about 300 ps.
- Attenuation lengths were measured, the average of the counters is 39.6 cm.
- Properties of the counters are being kept in a SQLite database.
- Measurements will be repeated every month going forward. Recall that one of the previous batches showed large deterioration in performance after about three months. One point on one bar went from 400 ps resolution to 650 ps due to visible surface crazing.
- Three of the paddles were handled with the wrong type of glove. These gloves had aloe vera on the surface. They were cleaned with isopropyl alcohol after this was realized.
We would like to have the readiness review at a point in time near being ready to assemble finished counters on the support structure. This will likely be in the early Fall.
We have to pick up the pace on the support structure, the test fixture, and the assembly fixture. One good thing is that the final drawings of the detector itself have all been done.