[Halld-pid] Time-of-Flight Meeting Minutes, May 19, 2015

[Mark Ito]

Folks,

Please find the minutes below and at

https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_May_19,_2015

   -- Mark
   ___________________________________

GlueX TOF Meeting, May 19, 2015
Minutes

Present:

  * *FSU*: Hussein Al Ghoul, Brad Cannon, Paul Eugenio, Sasha
    Ostrovidov, Aristeidis Tsaris
  * *JLab*: Mark Ito (chair), Simon Taylor, Beni Zihlmann


Announcements

  * Mark spoke to Sergey Boyarinov of Hall B. Turns out they did not do
    the bin-equalizing calibration on their CAEN TDCs. Beni reminded us
    that Bryan Moffit has released the library functions we need to do
    the calibration. We decided that it is worth doing for Hall D and
    the group will form a plan for doing it before the next run. Beni
    suggested that we talk to Sergey Furletov and see if we can get him
    to help since the code will have to be maintained by the online
    group in any case. As a first step Beni suggested downloading the
    values recommended by CAEN.


Review of minutes from May 5

We went over the minutes 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_May_5,_2015#Minutes>. 


Mike Staib is on board with the re-arrangement of the meaning of the 
timing calibration constants that we discussed last time. This clears 
the way for using our constants for the channel-to-channel time offsets.

Calibration Status FSU

Sasha has been looking at recent data with multiple hits per channel in 
both the FADCs and the TDCs. The second hit is often a cable reflection. 
For these events, he is exploring doing a time-walk correction by 
comparing the time difference measured by the ADCs and comparing it to 
the TDCs. When the second pulse is small reflection, the effect of time 
walk should be much greater for the second TDC hit.

Calibration Status JLab

Beni led us through recent work documented on his wiki page 
<https://halldweb.jlab.org/wiki/index.php/ADC_data#ADC_data>. See the 
page for details.

  * He sees the expected correlation between positions determined by
    end-to-end time difference in the TDCs and positions determined by
    the ratio of ADC amplitudes from the two ends of a counter.
  * After at time difference cut to select hits near the center of a
    counter, he sees clear Landau distributions in the energy deposition.
  * Added in press: he is also able to extract attenuation lengths from
    each counter. These show a long-range and short-range component in
    the relation of amplitude vs. distance from the PMT.


All of the these observation can serve as a basis for gain calibration 
and for future gain adjustments via high-voltage changes.

Retrieved from 
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