GlueX Start Counter Meeting, February 6, 2014
GlueX Start Counter Meeting
Thursday, February 6, 2014
10:00 am EST
JLab: CEBAF Center F326
- Review minutes from previous meeting
- Counter construction status
- Support structure construction status
- Electronics status
- Fast Shutdown
- Readiness review schedule
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- FIU: Werner Boeglin, Eric Pooser
- JLab: Eugene Chudakov, Chuck Hutton, Mark Ito (chair), Tim Whitlatch, Beni Zihlmann
Problem with Scintillator Manufacturer
Eric reported news from McNeal that the 50 pieces of scintillator received from Eljen were flawed. There are visible bubbles in the bend region and the edges are not in a single plane, i. e. there is a skew in the nose relative to the barrel. These pieces are clearly unacceptable.
McNeal will send them back to Eljen. Eric contacted Chuck Hurlbut of Eljen; they will investigate the cause. Currently the thinking is that the bend was overheated (thus the bubbles) and not held in place long enough during cooling (thus the skew). They are pressing new scintillator already. Eljen will not charge FIU for this batch. Note that the previous set of five counters looked very good in all aspects: visual appearance, shape, and timing resolution.
We estimated that this introduces a two-month delay in the schedule. June is now the target completion date for construction.
The assembly jig is coming together. FIU will start practicing with the five prototype counters so they will be ready when the production modules come in.
The new 3-layer carbon fiber inner sleeve is complete. The Rohacell foam should be in any day now. Machining and assembly should take four weeks.
Eric has seen a situation where, on the test stand, the aluminum support contacted some resistors on the SiPM board if the spacing between the two is not controlled. Chuck will check on this issue for the full detector.
Mark raised the question that Hovanes has posed to the groups about whether there are any special considerations for fast-shutdown systems that the controls group needs to know about. There seem not to be any equipment safety issues. Temperatures will be monitored via on-board thermisters. Those channels have been accounted for in the controls design. They can presumably initiate a shutdown of the MPOD, likely in the same way it is done for other SiPM-based read-out systems.
In light of the recent troubles with the scintillator, Mark passed on a reminder from Bruce Lenzer that we be sure to collect documentation from the manufacturer about pieces passing inspection at their facilities, at least a certificate of conformance.
Eric got an email from Mike Dugger about reviewing the start counter section of the current draft of the TDR. It appears to be quite a bit out-of-date right now. Eric will do an update and circulate a draft to the group.