GlueX TOF Meeting, November 3, 2015
GlueX Time-of-Flight Meeting
Tuesday, November 3, 2015
11:00 am EST
JLab: CEBAF Center, Room F326/327
- Review of minutes from September 22
- Calibration Status FSU
- Calibration Status JLab
- NIM Article
- The BlueJeans Meeting number is 350 531 998.
- Enter BlueJeans Meeting
Talks can be deposited in the directory
/group/halld/www/halldweb/html/talks/2015 on the JLab CUE. This directory is accessible from the web at https://halldweb.jlab.org/talks/2015/ .
- FSU: Hussein Al Ghoul, Brad Cannon, Sasha Ostrovidov, Aristeidis Tsaris
- JLab: Mark Ito (chair), Simon Taylor
There is a recording of this meeting at https://bluejeans.com/s/8MQf/ .
Calibration with Cosmics
Sasha gave a report on recent work.
- He has succeeded in taking cosmic data, but had a couple of difficulties:
- He needed to attempt to start runs several times before getting any triggers at all. He suspects that with multi-block readout of the CAEN TDCs, the token passing between modules would stop, hanging the system.
- ROCTOF1, which houses the FADCs, would crash in minutes from the start of the run. A hard reboot was needed to get things going again.
- This problem has resolved itself recently.
- In the end he got a few times 100 k events.
- The trend of higher gains at the edges of the arrays seen in beam data is also seen in cosmic data.
- This rules out the magnetic field, or a systematic problem using beam tracks.
- Possible culprits:
- Different HV supplies than those used at FSU.
- Different HV cables.
- He is working on a program to adjust HV to equalize gains. Data will be taken, gains measured, HV adjusted, and process iterated.
- He is also seeing a difference in the gain when comparing a hit in the middle of the paddle versus one near the ends, even after accounting for attenuation. The gain is about 10% higher near the ends.
- He is trying to judge the effect of gain calibration using a set of "tracks" in the TOF in cosmic data. He requires 5 counters minimum. The yield of such events is extremely low, about one part in ten thousand.
- The trigger rate is about 600 Hz.
- The threshold for a single FADC channel to be read out is 500 counts. The trigger threshold on the sum is about 50,000 typically, but other values have been tried.
- Brad is in contact with Sean Dobbs about a plug-in to be used in the calibration challenge.
- He is also cleaning up the script to drive the calibrations already done.