[Halld-pid] Time-of-Flight Meeting Minutes, August 16, 2016

[Mark Ito]

Folks,

Find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_August_16,_2016#Minutes 
.

   -- Mark

_____________________


    GlueX TOF Meeting, August 16, 2016, Minutes

Present:

  * *FSU*: Sasha Ostrovidov
  * *JLab*: Fernando Barbosa, Brad Cannon, Paul Eugenio, Mark Ito
    (chair), Simon Taylor, Beni Zihlmann


      Review of minutes from the previous meeting

We looked over the minutes from August 9 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_August_9,_2016#Minutes>. 


  * Although it is expected that the timing is worse for cosmics runs
    than for beam data, we do not have a detailed understanding of the
    mechanism.
  * Sasha reported a problem with the cosmic trigger: the energy
    threshold is expressed in 16 bits on the sum of all TOF counters and
    a single channel can cause the sum to exceed it. Beni will talk to
    Sasha about raising the threshold.


      TOF Efficiency

Beni showed scatter plots of efficiency for two runs: 10439 and 11508.

<https://halldweb.jlab.org/wiki/index.php/File:Run10439_eff.gif>
Run 10439
<https://halldweb.jlab.org/wiki/index.php/File:Run11508_eff.gif>
Run 11508

The plots show in the first column the distribution of track 
intersection points for tracks which match the TOF, for the vertical and 
horizontal paddles. The four plots in the second and third columns show, 
clockwise from top left, the charged track match efficiency for vertical 
paddles in 2-D bins of intersection position, the same for horizontal 
paddles, the efficiency for TOF points, and the efficiency in 2-D bins 
of charged track momentum versus polar angle.

Beni also showed efficiency as a function of run number for five paddle 
numbers both for horizontal and vertical plane.

Paddle eff run8 ver2.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Paddle_eff_run8_ver2.gif> 
Paddle eff run15 ver2.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Paddle_eff_run15_ver2.gif> 
Paddle eff run20 ver2.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Paddle_eff_run20_ver2.gif> 
Paddle eff run21 ver2.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Paddle_eff_run21_ver2.gif> 
Paddle eff run5 ver2.gif 
<https://halldweb.jlab.org/wiki/index.php/File:Paddle_eff_run5_ver2.gif>

Paddles 8 and 15 do not show much of an effect, but paddles 20 and 21 
show unstable efficiencies near the end of the run. These are the ones 
closest to the beam. Paddle 5, although far from the beam, shows 
instability. This is not understood at present. The inefficiencies may 
be a combination of reduced gain at high rates and simply two-pulse 
resolution probability being reduced at high rate.


      TDC Integral Non-Linearity Correction Calibration

Fernando reported that Ed Jastrzembski and Bryan Moffit are working on a 
scheme to obtain a non-linear correction for the CAEN TDCs. The TDCs are 
shipped from the factory with the correction pre-loaded, but that 
correction is based on a 40 MHz clock driving the boards; we run with 
41.667 MHz. Turns out that the correction depends on the clock rate. The 
correction is different for each chip, but each chip services several 
channels.

The exact scheme for obtaining and downloading new calibration tables 
have not been worked out yet. The data will be obtained in situ in the 
Hall. We will need to schedule time for doing this before the run.


      NIM Paper

Paul will be turning to the NIM paper as one of his high priority tasks 
in the coming weeks, as well as looking into fixtures for gluing new 
tubes on the counters if that becomes necessary.

Retrieved from 
"https://halldweb.jlab.org/wiki/index.php?title=GlueX_TOF_Meeting,_August_16,_2016&oldid=76876"

  * This page was last modified on 16 August 2016, at 15:10.


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

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