GlueX TOF Meeting, June 30, 2015

From GlueXWiki
Jump to: navigation, search

GlueX Time-of-Flight Meeting
Tuesday, June 30, 2015
11:00 am EDT
JLab: CEBAF Center, Room F326/327


  1. Announcements
    1. Access Control for JLab Drawings (Beni)
    2. Kaon ID via TOF demonstrated
  2. Review of minutes from May 19
  3. Calibration Status FSU [1]
  4. Calibration Status JLAB



Talks can be deposited in the directory /group/halld/www/halldweb/html/talks/2015 on the JLab CUE. This directory is accessible from the web at .



  • FSU: Hussein Al Ghoul, Paul Eugenio, Sasha Ostrovidov, Aristeidis Tsaris
  • JLab: Eugene Chudakov, Mark Ito (chair), Simon Taylor, Beni Zihlmann


  • Beni announced a new policy for official drawings at the Lab. Access will be by request only in the future. Eugene mentioned that there may be an exemption for specific drawings so that they can be posted on the web.
  • Yesterday at the Physics Meeting, Paul Mattione showed plots of β vs. momentum using the TOF that showed clearly separated pion, kaon, and proton lines.

Calibration, FSU

Sasha showed some plots from his work using cable reflections to obtain time-walk corrections. See his webpage for details.

In the time difference between two pulses in a given channel in the CAEN TDCs, he sees two peaks, one at 150 ns separation and on at 190. These two peaks are present for all channels. The time difference between successive peaks in the FADC shows a single peak at 190 ns separation. A plot the FADC two-pulse separation vs that of the TDC shows that these peaks are spurious, probably due to reflections, thought the rich structure seen is hard to understand. Sasha also showed various plots looking for a dependence on the pulse separation with FADC amplitude. He had hoped that this dependence could be used as the basis for time-walk corrections. The lack of a clear dependence on FADC amplitude makes this look hard to do.

Calibration, JLab

Beni showed results in two areas.

Attenuation Lengths

Beni has studied attenuation lengths on a counter by counter basis. He fits the pulse integral for a single end in the FADCs in bins of position along the counter as measured by TDC time difference. The resulting points are fit to two exponentials. The short attenuation length is about 76 cm and the long one is around 500 cm. He showed the distribution of these attenuation lengths separately. See his wiki page for details.

FADC time differences vs. TDC time differences

Beni sees the expected correlation between end-to-end time difference measured by the TDCs vs. that measured by the FADC. However the relation has a measurable non-linearity; he parametrized this as a sine (in the region around 0 a linear function at lowest order). The reason for the non-linearity is not understood at present. Again see his wiki page for the plots.

Automating the Calibration

Mark brought up the issue. We still have work to do on this front. The current constants are produced with a well-defined procedure but not easily automated in its current form.