[Halld-pid] Time-of-Flight Meeting Minutes, January 31, 2018

[Mark Ito]

Folks,

Please find the minutes below and at

https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_31,_2018#Minutes

   -- Mark

__________________________________________


    GlueX TOF Meeting, January 31, 2018, Minutes

Present:

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

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


      Review of minutes from the previous meeting

We went over the minutes from the meeting on January 3 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_3,_2018#Minutes> 
without significant comment.


      Calibration Status

  * Beni performed a step-by-step calibration of recent data using run
    40460, interactively on the ifarm. Comparison with previous
    constants show only small differences. Only a few channels show
    significant differences (50 to 100 ps). He characterized the
    agreement as "amazing". The database has not yet been updated with
    these constants.
  * Beni took the Spring 2017 constants for ADC vs. TDC time difference
    (channel-by-channel) and used them as the constants for recent
    running in the CCDB. Sean reported significant improvement in timing
    results. The relevant monitoring plots look good now.
  * Beni spoke to Ashley Ernst about her taking responsibility for the
    TOF calibration.


      Low Efficiency in High-Rate Counters

Beni first did the analysis that showed this problem. There were no 
updates at this meeting.


      Amplified Base Prototype

Beni has started to look at data taken recently with the test counter in 
the Hall. One end has a standard PMT, the other has a PMT with an 
amplifier in the base, designed and built by Vladimir Popov.

  * He looked at TDC times vs. ADC times to get time walk corrections
    for these two new channels.
  * After walk correction, the t_TDC -t_ADC distribution of the
    amplified end looks better than that of the un-amplified end, the
    former with an RMS of 160 ps vs. 300 ps for the latter. Beni
    suspects that the HV is lower than optimal on the un-amplified end.
  * He plotted the time difference in the test counter vs. the time
    difference of a standard counter in the TOF (paddle 14, plane 0).
    These counters are in orthogonal orientations. There is a clear blob
    where coincidences appear. The RMS spread of the blob is worse for
    the test counter (220 ps) than for the standard counter (220 ps).
  * These results are preliminary. Beni has more to go on his first set
    of analysis ideas.

Overall the on-base amplifier seems to performing reasonably well. We 
await further results.


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

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