[Halld-pid] Time-of-Flight Meeting Minutes, February 21, 2017

[Mark Ito]

Folks,

Find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_February_21,_2017 
.

   -- Mark

_______________


    Minutes

Present:

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

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


      Announcements

  * *Lucite Shield Simulation*. Thomas has had a possible issue with his
    environment. He is rerunning the simulation now.


      Review of minutes from the previous meeting

We went over theminutes from February 7 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_February_7,_2017#Minutes>. 
There were no significant comments.


      Run Status

  * Sasha is the run coordinator until tomorrow.
  * He reported the the occupancy plots look good, one set of scalars
    [ADCs?] for the TOF is missing in EPICS.
  * Even with the Lucite shield, the upstream plane shows a higher
    scalar rate than the downstream, by 50%. It will be interesting what
    the Monte Carlo has to say about this.


      Calibration

Beni reported that the timing calibrations are being re-run now for all 
runs.

Also we need to get started on comparisons of efficiency and resolution 
between data and Monte Carlo. Simon has been working on improving the 
matching between charged tracks and the TOF.


      New PMT bases

Beni presented results fromtests with the new base 
<https://halldweb.jlab.org/wiki/index.php/PMT_rate_tests>with on-board 
amplifier from Vladimir Popov. (See his wiki page for details and plots.)

He did the tests with a standard PMT and one with a modified base. He 
reproduced the collapse of pulse height for the standard base at 1300 V 
and a rate of 10 MHz from the laser. The amplitude was adjusted to be 
that of a minimum ionizing TOF hit. The modified base went to 10 MHz 
with signal collapse but only after the voltage on the tube was reduced 
to 1000 V. Under those conditions a 18 mV DC offset appears on the 
baseline. We need to ask Vladimir about the inductive coupling scheme he 
proposed at one point.

Vladimir suggested a test in the Hall. We discussed options. Beni 
suggested shipping a half-width counter from the mini-TOF from FSU to 
JLab and mounting it in the Hall, location to be determined. In front of 
the TOF? Behind the FCAL? Paul thought that we could get it here with a 
week's notice so doing it this run seemed not impossible. We will have 
to talk to Tim Whitlatch and Tom Carstens about the feasibility of 
mounting and possible locations.

We would also like to know if the PMT gains have remained stable during 
the current run with the new reduced voltages.


      PMT Replacement

Several comments were made and questions asked.

  * Can amplifiers be added to the bases in situ, i. e., without
    dismounting the planes from the FCAL carriage?
  * Can the gain loss suffered by the inner PMTs be compensated by
    running them at higher voltage?
  * Has the performance of the PMTs deteriorated during the current run
    now that they are being run at lower voltage?
  * Which PMTs do we want to replace?
  * Do we need to build more gluing fixtures to facilitate PMT replacement?
  * What are the schedule constraints for producing the amplifier
    electronics?

Retrieved from 
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  * This page was last modified on 25 February 2017, at 19:26.

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