GlueX TOF Meeting, June 20, 2013
GlueX TOF Meeting
Thursday, June 20, 2013
10:00 am EDT
JLab: CEBAF Center, F326/327
- 1 Agenda
- 2 Communication
- 3 Minutes
- Review of last TOF bi-weekly meeting
- Construction news
- Reflections from the splitters 
- Iron shield drawings  
- Shield at cathode voltage
- Adding frame part machining to contract
- Installation plan and document
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Talks can be deposited in the directory
/group/halld/www/halldweb/html/talks/2013-2Q on the JLab CUE. This directory is accessible from the web at https://halldweb.jlab.org/talks/2013-2Q/ .
- FSU: Paul Eugenio, Sasha Ostrovidov
- JLab: Chuck Hutton, Mark Ito (chair), Beni Zihlmann
Adding frame part machining to contract
We decided to add the machining of parts for the TOF frame that FSU will undertake as an additional activity in the contract. This should not delay specification of the work or procurement of materials.
Iron shield drawings
We looked at the drawings Chuck has done of the outer iron magnetic shields. There are two versions, one for the standard counters and another for the half-width counters. These will machined at FSU and Paul will show these to the shop folks at FSU to get the ball rolling.
Color scheme for these shields was the subject of too much discussion.
Rail system for supporting the TOF
Chuck showed the current design for supporting the TOF from the FCAL frame. The weight is supported on rails that will allow the TOF move upstream from its running position by about two feet to allow access to the downstream face of the TOF and the upstream face of the FCAL. Note that the strain relief for the cables are not shown on these drawings.
The TOF will be brought in on a crane and placed on the rails. There will be some guide rails at the bottom. The exact procedure for supplying the force to move it on the rails is TBD.
Review of minutes from the last meeting
- The splitters have arrived at FSU.
- The two LeCroy high voltage cards have arrived at FSU.
- Paul will send us a set of links to the procedures so that we can capture a copy at JLab for archival purposes.
- Chuck will look into finding a good time for an assembly/installation next week.
- Gluing fixture now accommodates 9 modules at a time.
- 13 completely wrapped modules now.
- 9 standard and 2 half-width glued with light guides, ready for wrapping, moving to storage. Will wrap in groups of eight.
- Students being moved from polishing to wrapping work.
- Will start gluing another nine bars soon.
- Issue with light leaks: some modules had Tedlar wrapping damaged during transport in moving structure. Light leak testing, based on PMT current, now instituted into the procedures. Once found leaks are easily fixed. Now all modules will be wrapped in felt after wrapping, and will remain so wrapped through shipping to JLab.
- Rubber caps will be installed on the unused dynode BNC connector on the PMTs for marking ("do not use") and protection.
- The test system is being modified to use the Flash-250.
- Sasha now understands the dip in the end-to-end time-difference spectrum seen with the linear fan-in/fan-out. It was due to a lack of efficiency introduced when the pulses were in coincidence as the FI/FO.
- He also reports that he sees double pulses about 10% of the time when using the 50-50 passive splitters in the test set-up. He attributes this to signal reflections from the splitter. See his plots on the same wiki page as above. This will require further investigation.
- Sasha proposes that we gain balance tubes in the test set-up (same wiki page) using dead reckoning rather that do a series of measurements to iteratively adjust the gains with cosmics, which may be quite time consuming. We thought that that was a reasonable proposal.
Shield at cathode voltage
Paul looked up the "HA" coating that comes with our Hamamatsu tubes. This obviates the need to do any external connection to cathode voltage on the shield or other surrounding metal structure.