GlueX TOF Meeting, July 26, 2016
GlueX Time-of-Flight Meeting
Tuesday, July 26, 2016
11:00 am EDT
JLab: CEBAF Center, Room F326/327
- Review of minutes from the previous meeting
- PMT order
- Cosmic data
- Calibration Updates
- NIM paper
- The BlueJeans Meeting number is 350 531 998.
- Enter BlueJeans Meeting
Talks can be deposited in the directory
/group/halld/www/halldweb/html/talks/2016 on the JLab CUE. This directory is accessible from the web at https://halldweb.jlab.org/talks/2016/ .
- FSU: Sasha Ostrovidov
- JLab: Eugene Chudakov, Mark Ito (chair), Simon Taylor, Beni Zihlmann
There is a recording of this meeting on the BlueJeans site.
Review of minutes from the previous meeting
We went over the minutes from July 19. No significant comments.
Ardavan Ghassemi of Hamamatsu sent us an email cautioning us that the current PMT model used in the TOF will be discontinued as some point soon. He proposes a replacement model and sent along a data sheet for the R13435. The new tube has a diameter about 1 mm greater than the old.
Beni led us through his plots:
- looking at signal amplitude vs time difference for 1350V
- The flash250 ADC op-amp signal inverting input causes a baseline shift that feeds back to the input to the leading edge discriminator resulting in a miss match between threshold setting and actual threshold.
- other examples of amplitude vs dt paddle 18 plane 1:
- or paddle 20 plane 1:
- or paddle 20 plane 2:
- and the same PMT but 100V higher at 1450V:
The DC shift in the baseline at the discriminator from the FADC can be as much as 35 mV and depends on the FADC channel. We will need to have channel-by-channel discriminator settings, especially when running the tubes at lower gain.
The next step is to try and look at time resolution at new reduced voltages.
We will meet again in a week.