[Halld-pid] Time-of-Flight Meeting Minutes, August 5, 2014

[Mark M. Ito]

Folks,

Please find the minutes below and at 
https://halldweb1.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_August_5,_2014#Minutes 
.

   -- Mark
_____________________________________

GlueX TOF Meeting, August 5, 2014
Minutes

    Present:
      * FSU: Brad Cannon, Paul Eugenio, Sasha Ostrovidov, Aristeidis Tsaris
      * JLab: Mark Ito (chair)

Meeting Time

      * We will meet once a week on Tuesday's until further notice.
      * Mark will look for another meeting room so that he can get in to
        set things up a bit earlier. The time of the meeting may or may not
        change as a result.

Man-Lift Training

    Paul took the training last week at JLab. He is now authorized to use
    the man-lift in the Hall.

EPICS Read-Out of Discriminator Scalars

    No word on this from Sergey Boiarinov yet.

Hardware Items

    Paul gave a report.
      * FSU stickers have been deployed on the TOF. They look marvelous, it
        was alleged.
      * Light leaks were found in a few regions where the main bolts that
        apply support pressure on the light guides pass next to the
        counters. Abrasion of the Tedlar was observed at some of these
        positions. Note that these are in the corners of the frame. These
        leaks were likely introduced during assembly.
      * A few leaks were found in the middle of the array. It is possible
        that there were nicks due to the cross supported added temporarily
        during the lifting.
      * In both cases point away from any systematic cause of leaks due to
        flaws in counter design or individual counter assembly procedures.
      * In the process, FSU has developed techniques for leak-hunting
        in-situ in the Hall. In particular they can now monitor rates using
        the wireless network and a cell phone, which gives immediate
        feedback anywhere in the Hall.
      * A small, but not insignificant fraction of the DMD wrapping around
        the light guides are detaching. These were meant for surface
        protection, especially during assembly of the counters on the
        support frame. Paul is fixing them as he encounters loose ones, but
        operation of the counters should be affected in any case.
      * Reference marks were made on the inside of the steel magnetic
        shields on the bottom of the array. These will be used to judge
        whether there is any mechanical shifting of the vertically-oriented
        counters due to gravity over time.
      * Sasha elaborated on the nature of the leaks as they appeared in the
        scalars. Rates were compared with the lights in the Hall on and
        off. He has established a taxonomy:

    leak type factor rate increase with lights on vs. dark
    macro     5-10
    mini      2
    micro     1.5
    nano      1.15 or less
      * No macro leaks have been found since installation on the forward
        carriage. The abraded Tedlar gave mini leaks. Typical rates for
        good counters are roughly 400 Hz or less.
      * There are two channels with elevated base rates that do not change
        when turning on the lights. They seem to have ringing on the tails
        of the pulses. These are being operated at 50 or 100 V below
        nominal right now.

Calibration

    Sasha has been working on calibrating the TOF using cosmic data from
    the Hall. To start with he is working on:
      * timing
      * speed-of-light
      * time-walk corrections

    For events with three or more counters hit in a plane he fits a
    straight line to the trajectory as reported by end-to-end timing. He is
    finding that a few events with difficult configurations of counters can
    throw off convergence of the the method. He is working on selection
    criteria that will give robust results once applied.

    He mentioned that he would like a sample of a million events. So far he
    has been working with about 20 k events. He will take more data,
    operating the DAQ remotely from FSU.

    Sasha also mentioned that as far as he knows there was no calibration
    of the least-count time bin size for the CAEN TDCs other than that done
    at the factory. The software he developed for doing this at FSU cannot
    be used for the set-up in the Hall. Mark will look into what tools are
    available at the Lab to do this.

Stand-Alone Event Display

    Aristeidis reported more progress on the stand-alone event display GUI.
    He has compared pictures with dumps of the raw data to check
    correspondence. He worked out some confusion having to do with the
    classic looking-upstream/looking-downstream perspective problem.

Scalar GUI

    Brad has been working on a GUI to display the scalar information in
    graphical form. He is stuck on the transfer of data from the ROC to a
    host computer. For now he is composing the GUI image on the ROC itself,
    but displaying this at FSU is extremely slow. We discussed strategies
    for moving forward. Brad is in touch with David Lawrence on how to do
    the ROC to host data transfer.

Meeting Time Change

    Notwithstanding our discussion at the outset of the meeting we may move
    the time of the meeting to a more convenient time.

-- 
Mark M. Ito, Jefferson Lab, marki at jlab.org, (757)269-5295