[Halld-pid] Time-of-Flight Meeting Minutes, June 6, 2018

[Mark Ito]

Folks,

Please find the minutes below and at

https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_June_6,_2018#Minutes

   -- Mark

______________


    GlueX TOF Meeting, June 6, 2018, Minutes

Present:

  * *FSU: * Sasha Ostrovidov
  * *JLab: * Mark Ito (chair), Simon Taylor, Beni Zihlmann

There is a recording of this meeting <https://bluejeans.com/s/Gar0v/> on 
the BlueJeans site. Use your JLab credentials.


      Review of Minutes from the May 23 Meeting

We reviewed the minutes 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_May_23,_2018#Minutes> 
without comment.


      Calibration Status

Beni gave the report. Calibration is complete. All runs for which Sean 
Dobbs produced files are done. The constants obtained have not been 
written to the CCDB yet.


        Checking stability of the timing constants

  * The downstream plans appears less stable than the upstream.
  * For some PMTs, isolated runs show large excursions. These are likely
    due to failures in the calibration program for these channels. These
    only appear in the downstream plane and not the upstream, against
    naive expectations.
  * We may have to revisit calibrations for selected channels.


        Variations in the signal amplitude

Beni showed plots of signal amplitude versus run number for two of the 
PMTs.

Pmt19 amplitude.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Pmt19_amplitude.gif>

PMT 19 is in near the beam line in the downstream plane. Note that the 
gain seems to have dropped 12-15% over the course of the run.

Adc mpv pmt110 new1.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Adc_mpv_pmt110_new1.gif>

PMT 110 is also near the beam line in the upstream plane. Note the rise 
in gain around run 41900. Beni sees extra noise in the HV voltage 
read-back around this time, but the cause of the rise is still under 
investigation.


      TOF Upgrade

Sasha reported that Paul Eugenio has the FSU shop working on a mock up 
the the central region of a newly configured TOF. In particular they are 
trying ideas for how the light guides for the half-width paddles should 
be shaped.

Also, in July, Paul is planning on coming up to the Lab. He wants to 
paint the ends of half-length paddles black so that there is little 
contribution from light reflected from the beam-adjacent face of the 
counters.

-- 
Mark Ito, marki at jlab.org, (757)269-5295

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