GlueX TOF Meeting, August 5, 2014
GlueX Time-of-Flight Meeting
Tuesday, August 5, 2014
10:00 am EDT
JLab: CEBAF Center, F227
- Meeting schedule clarification
- Review of July 22 Meeting
- Installation Update
- The BlueJeans Meeting number is 350 531 998.
- Enter BlueJeans Meeting
Talks can be deposited in the directory
/group/halld/www/halldweb/html/talks/2014-3Q on the JLab CUE. This directory is accessible from the web at https://halldweb.jlab.org/talks/2014-3Q/ .
- FSU: Brad Cannon, Paul Eugenio, Sasha Ostrovidov, Aristeidis Tsaris
- JLab: Mark Ito (chair)
- We will meet once a week on Tuesday's until further notice.
- Mark will look for another meeting room so that he can get in to set things up a bit earlier. The time of the meeting may or may not change as a result.
Paul took the training last week at JLab. He is now authorized to use the man-lift in the Hall.
EPICS Read-Out of Discriminator Scalars
No word on this from Sergey Boiarinov yet.
Paul gave a report.
- FSU stickers have been deployed on the TOF. They look marvelous, it was alleged.
- Light leaks were found in a few regions where the main bolts that apply support pressure on the light guides pass next to the counters. Abrasion of the Tedlar was observed at some of these positions. Note that these are in the corners of the frame. These leaks were likely introduced during assembly.
- A few leaks were found in the middle of the array. It is possible that there were nicks due to the cross supported added temporarily during the lifting.
- In both cases point away from any systematic cause of leaks due to flaws in counter design or individual counter assembly procedures.
- In the process, FSU has developed techniques for leak-hunting in-situ in the Hall. In particular they can now monitor rates using the wireless network and a cell phone, which gives immediate feedback anywhere in the Hall.
- A small, but not insignificant fraction of the DMD wrapping around the light guides are detaching. These were meant for surface protection, especially during assembly of the counters on the support frame. Paul is fixing them as he encounters loose ones, but operation of the counters should be affected in any case.
- Reference marks were made on the inside of the steel magnetic shields on the bottom of the array. These will be used to judge whether there is any mechanical shifting of the vertically-oriented counters due to gravity over time.
- Sasha elaborated on the nature of the leaks as they appeared in the scalars. Rates were compared with the lights in the Hall on and off. He has established a taxonomy:
|leak type||factor rate increase with lights on vs. dark|
|nano||1.15 or less|
- No macro leaks have been found since installation on the forward carriage. The abraded Tedlar gave mini leaks. Typical rates for good counters are roughly 400 Hz or less.
- There are two channels with elevated base rates that do not change when turning on the lights. They seem to have ringing on the tails of the pulses. These are being operated at 50 or 100 V below nominal right now.
Sasha has been working on calibrating the TOF using cosmic data from the Hall. To start with he is working on:
- time-walk corrections
For events with three or more counters hit in a plane he fits a straight line to the trajectory as reported by end-to-end timing. He is finding that a few events with difficult configurations of counters can throw off convergence of the the method. He is working on selection criteria that will give robust results once applied.
He mentioned that he would like a sample of a million events. So far he has been working with about 20 k events. He will take more data, operating the DAQ remotely from FSU.
Sasha also mentioned that as far as he knows there was no calibration of the least-count time bin size for the CAEN TDCs other than that done at the factory. The software he developed for doing this at FSU cannot be used for the set-up in the Hall. Mark will look into what tools are available at the Lab to do this.
Stand-Alone Event Display
Aristeidis reported more progress on the stand-alone event display GUI. He has compared pictures with dumps of the raw data to check correspondence. He worked out some confusion having to do with the classic looking-upstream/looking-downstream perspective problem.
Brad has been working on a GUI to display the scalar information in graphical form. He is stuck on the transfer of data from the ROC to a host computer. For now he is composing the GUI image on the ROC itself, but displaying this at FSU is extremely slow. We discussed strategies for moving forward. Brad is in touch with David Lawrence on how to do the ROC to host data transfer.
Meeting Time Change
Notwithstanding our discussion at the outset of the meeting we may move the time of the meeting to a more convenient time.