[Halld-pid] Time-of-Flight Meeting Minutes, September 6, 2016

[Mark Ito]

Colleagues,

Please find the minutes below and at 
https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_September_6,_2016#Minutes 
.

   -- Mark

___________________


    GlueX TOF Meeting, September 6, 2016, Minutes

Present:

  * *JLab*: Eugene Chudakov, Mark Ito (chair), David Lawrence, Simon
    Taylor, Beni Zihlmann


      High Intensity Running Issues with the TOF

David showed slides 
<https://halldweb.jlab.org/wiki/images/0/08/20160906_simulation.pdf> 
illustrating the need to reduce the data volume from the TOF at high 
rate. The slides were from the Level 3 review.

The per crate limit is 1 Gbit/s as presently configured. We could 
upgrade the NIC to give 10 Gbit/s, but the VME backplane would limit us 
at about 1.5 Gbit/s. Crates TOF1 (with FADCs) and TOF2 (with TDCs) are 
two of the big contributors relative to other crates in the system. The 
amount of data can be reduced by tightening timing windows, enough to 
operate at high rates from a bandwidth perspective. For the TDCs the 
window is currently several microseconds wide. The reduction possible 
for the FADCs from time window tightening is not as great. Beni is 
afraid that raising the sparsification threshold may not do to much 
good; a lot of the hits are real particles. To get to high rate, we may 
have to upgrade the NIC for the flashes.

Eugene pointed out that the central part of the TOF may not be usable at 
high rate anyway. That needs to be studied, and alternative approaches 
explored.


      Review of minutes from the previous meeting

We briefly looked at the minutes from August 23 
<https://halldweb.jlab.org/wiki/index.php/GlueX_TOF_Meeting,_August_23,_2016#Minutes>. 
Brad Cannon is meeting with Mark and Beni weekly now, with the exception 
of this week; he is away on travel.


      TOF Analysis Status and Run Plan

Beni reviewed progress and plans for developing new high voltage 
set-points.

  * The analysis of HV scan runs, 10838-10845, 10646, and 10648 is now
    complete. The outer counters look to be efficient at 1200 V or
    perhaps a bit less. The picture from the inner counters is not as
    clear, but the low voltage points in the scan show voltage settings
    comparable to those of the outer counters.
  * The four hours of data used by the HV scan provided sufficient data
    for gain calibration and determining HV set points. We have asked
    for six hours for this run. We should run at nominal beam intensity
    to see if any problems with rate are still present at lower voltage.
  * Beni plans to run at a variety of fixed voltages for all tubes to
    simplify operations. Recall that with the Spring 2016 scan, voltages
    were adjusted with reference to their nominal value.


      CAEN TDC calibration

Beni reminded us that we have not heard any recent news about the 
calibration to correct for the CAEN TDC system clock running at 41.7 MHz 
rather than 40 MHz. We need to look into what the plans are for this 
activity and schedule it.



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