[Halld-pid] Time-of-Flight Meeting Minutes, January 24, 2017

[Mark Ito]

Flight Timers,

Find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_24,_2017#Minutes 
.

   -- Mark
_________________________


    Minutes

Present:

  * *FSU*: Sasha Ostrovidov
  * *JLab*: Thomas Britton, Brad Cannon, Mark Ito (chair), Simon Taylor,
    Beni Zihlmann
  * *NU*: Sean Dobbs


      Announcements

  * The Hall closes on Friday.
  * Beam due in Hall on Monday during the day.


      Review of minutes from the previous meeting

We looked over the minutes from January 10 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_January_10,_2017#Minutes>. 
No significant comments were made.


      Run Readiness

  * *FADC Replacement*. Sascha Somov confirms that the broken FADC that
    Beni identified is indeed bad and Sascha will replace it. After that
    Beni will ask Sergey Furletov to do a pedestal setting. And after
    that Beni will look for channels that have missing bits on their
    DACs and either (a) set the pedestals by hand or (b) replace the
    units if spares are available.
  * *Online Monitoring*. We need a routine such that problems like the
    bad FADC are caught early. Brad has discussed the issue with David
    Lawrence; there will be an on-going display of the critical
    monitoring histograms in the counting room. There should also be a
    set of standard "good" plots with which to compare. Also it would be
    nice if there was some sort of histogram-viewing activity on the
    checklist for shift takers. Thomas volunteered to look into these
    issues.
  * *Hot Check-Out*. Beni, Brad, Thomas will get together and check
    things out.


      HV scan

Brad's HV setting jobs are done as of this morning. There were some 
issues getting the latest version of the code from Beni, but those have 
been sorted. The HV values agree with Beni's within a few percent. These 
are for the double-ended counters; single-ended HV values are still to 
come.

Sean asked about resolution and efficiency with the lower voltages has 
been studied by the group. He showed some plots from the monitoring 
plots that show poorer resolution now (at 1200 V for all counters) than 
in the spring, 140 ps vs. 100 ps for pi-, obtained after Beni's most 
recent calibrations. Beni will try to confirm these results.

Beni repeated a test with a new tube using the laser in the lab. At 1300 
V, he can go to 10 MHz without degradation of the pulse amplitude. At 
1500 V, this is no longer the case.

Sean showed other plots showing the rate of TOF hit matches with charged 
tracks. There is clearly a drop off for the half-width counters. Beni 
things that that is due to degradation in gain for those tubes because 
of high currents last Spring. A channel-by-channel HV setting should 
bring those back. Beni also thinks that after this run, we should 
replace some of these inner tubes.

Sean remarked that until recently, with the uploading of Beni's new 
constants, the poor TOF timing was holding up calibration, having 
effects in several other detectors. Getting good TOF constants early 
should be a priority this time.


      Lucite Shield Simulation

Thomas is working on a simulation of rates in the TOF with and without 
the Lucite shielding that was installed in December. He is almost there. 
He still needs some details of the geometry, in particular the 
dimensions of the inner sleeve that fits inside the beam hole. If he 
sees an effect comparable to that see in data, then we can study how we 
might optimize the arrangement.

Retrieved from 
"https://halldweb.jlab.org/wiki/index.php?title=GlueX_TOF_Meeting,_January_24,_2017&oldid=79385"

  * This page was last modified on 26 January 2017, at 13:29.


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

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/halld-pid/attachments/20170126/aee44a09/attachment.html>