GlueX TOF Meeting, August 9, 2016

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GlueX Time-of-Flight Meeting
Tuesday, August 9, 2016
11:00 am EDT
JLab: CEBAF Center, Room F326/327

Agenda

  1. Announcements
  2. Review of minutes from the previous meeting
  3. PMT order
  4. TOF rates during lumi scan
  5. Cosmic data
  6. Calibration Updates
  7. NIM paper

Communication

Slides

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/ .

Minutes

Present:

  • FSU: Sasha Ostrovidov
  • JLab: Eugene Chudakov, Mark Ito (chair), Simon Taylor, Beni Zihlmann

There is a recording of this meeting on the BlueJeans site.

PMT Order

The order for the initial 25 PMTs has been issued as a PO. The order for an additional 6 is in the system, signed, and assigned a buyer.

TOF rates during lumi scan

Beni looked at runs 11634-11637. He plots TOF rates as recorded by EPICS (per PMT) vs. electron beam current from the luminosity scan at the end of the Spring 16 run for selected paddles. Recall that paddle 1 to 19 are regular width/length paddles, paddle 20 and 21 are narrow width long paddles and paddle 22 is a short single ended paddle.

The rates are in Hz as a function of beam current in nA. The data are from runs 11634 to 11637 where luminosity scans were done from 40 to 140nA. The collimator was set to 5mm diameter and the radiator is 3x10-4 with LH target full.

TOF PMT rates.gif

Beni noted that if the intensity goes up by a factor of five, the highest rate counters will be unusable. Mitigations: shielding? higher magnetic field?

Cosmic data

Beni showed histograms of the mean time difference between paddle 21 of both planes, both for recent cosmic data at various voltages and for a run during this past Spring with the photon beam.

1200V
1250V
1500V
Spring '16, run 11666

There is not a marked difference in resolution between the various voltage settings for the cosmic data. However, all settings show poorer resolution and than the beam data. Clearly, the beam data has much better conditions for timing resolution measurements. If there is a trend in the cosmic data with voltage setting, it might be masked by the effect of the cosmic conditions.

Sasha suggested a position cut (time-difference cut) to ensure that the cosmic hits are coming from the "intersection" region defined by the crossed counters. This might clean things up for the cosmics. Beni will try that.

Beni also noted that although the gain on the inner counters has been reduced, he does not see any dead counters in the cosmic runs.

Next Meeting

We will meet again in a week.