[Halld-pid] Time-of-Flight Meeting Minutes, May 8, 2019

[Mark Ito]

Folks,

Please find the minutes here 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_May_8,_2019#Minutes> 
and below.

   -- Mark

_________________________________________________________


    Minutes, GlueX TOF Meeting, May 8, 2019

Present:

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

There is a recording of this meeting <https://bluejeans.com/s/K8rxT/> on 
the BlueJeans site. Use your JLab credentials to access it.


      Review of minutes from the last meeting

We looked at the minutes from the meeting on April 24 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_April_24,_2019#Minutes>. 
Mark did end up buying the mill bit and the scintillator modules as per 
Paul's specs.


      Upgrade Reports

  * Paul reported that the scintillator order was received by Eljen.
    Delivery to FSU is expected May 31.
  * More light guide material will be needed. There is another run
    planned at the factory this month. Paul is reluctant to try a
    different manufacturer since the material from this one has been
    problem-free.
  * Beni has had a second look at the electronics situation. We seem to
    be OK. Fernando Barbosa is aware of what we will need.
  * Tim reported that the technical staff is all ready to go on the job
    of unmounting the TOF and laying it horizontal in the Hall. Work can
    start as soon as the current tasks on the DIRC have been completed.
  * Paul will send photos of the arrays during the initial installation.
    He would like it if the orientation could be the same as it was last
    time.


      Air Light Guides

Sasha has been testing joining the half-length counters optically across 
the beam hole region with an air channel; essentially extending the 
ESR/Tedlar wrapping across the gap. He has been using the half-length 
counters from the mini-TOF at FSU. Looking at scaled coincidence rates 
of cosmics using an end-to-end coincidence of a full-length counter as 
trigger, he sees the following probabilities of seeing a signal in one 
half-length counter when the other one fires:

HV (V) 	Hit Probability (%)
1200 	3
1300 	18
1400 	60

However if an additional scintillator is added to the coincidence to 
insure a cosmic hit near the air light guide (within 6 cm), the 
other-counter-hit-probability increases to 90% at 1400 V.

Sasha is repeating the study with a full data acquisition system.

Beni suggested some stiffening material for the walls of the light guide 
(low mass, e. g., cardboard).

There was some discussion of support for the ends of the counters around 
the beam hole. This would be complicated by the presence of air light 
guides.


      Geometry

Ashley pointed out that we will need to modify the geometry of the TOF 
for the upgraded configuration. She will look into how much work is 
involved in that.


      Collaboration Meeting

Paul will give a report at next week's collaboration meeting on the 
status of the upgrade.


      Calibration

Beni has started calibrating the Spring 2019 data. Results are hard to 
check because of the absence of tracking. Simon pointed out that the FDC 
was on for a few runs; perhaps those runs can be examined.

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  * This page was last modified on 8 May 2019, at 13:47.

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