Time-of-Flight/Start-Counter/Target Meeting, November 13, 2009

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Location, Time

Friday, November 13, 2009
2:00 pm EDT
JLab: CEBAF Center, Room F326/7
ESNet: 8542553
EVO: direct meeting link
Conference Group: 800-377-8846, participant code: 77438230
Slides: talks can be deposited in the directory /group/halld/www/halldweb1/html/talks/2009-11 on the JLab CUE (you have to be a member of the "halld" group). This directory is accessible from the web at https://halldweb1.jlab.org/talks/2009-11/ .

Agenda

  1. Minutes from the last meeting
  2. Time-of-Flight Status
  3. Start Counter Status
  4. Target Status
  5. Action Items

Minutes

FIU: Werner Boeglin
FSU: Sasha Ostrovidov
JLab: David Lawrence, Mark Ito (chair), Sascha Somov, Aram Teymurazyan
UMass: Rory Miskimen

Time-of-Flight Status

Sasha O. gave us an update:

  • The cross-talk problem reported at the last meeting has been reduced to a few percent of the neighboring channel pulses. Many things were checked; the identity of the magic bullet is not known.
  • A 4 ns delay cable is being used on the Phillips discrimintor as suggested by Beni Zihlmann.
  • With the new set-up he is seeing 100 ps resolution on the time difference. This is to be compared with the 124 ns he saw with the CAEN VME discriminator.
  • He is now running cosmic tests with an Ortec CF 8000??? discriminator.
  • No time walk corrections have been applied to any of the tests so far.
  • Sascha S. raised the possibility that rate considerations might argue for leading-edge discriminators. David pointed out that with a time-walk corrections, the leading-edge discriminator might do as well in offline reconstruction as a constant-fraction model.
  • Sasha O. is still hoping to get a flash ADC from JLab.

Start Counter Status

Werner started to report on light output studies he has been doing, but most of his report had to be postponed due to technical audio difficulties of unknown origin. Mark and Werner will investigate.

Mark recapped some notes from a conversation with Sascha S. about start counter geometry:

  • Werner has a python (perl?) script that generates an HDDS specification of the start counter, including rohacell support and light guides. Seem like this works, more or less.
  • Tim/Chuck have some version from the past that has an uncertain relationship to the latest design.
  • The version in HDGeant presently is pretty close to Werner’s latest thinking.
  • Essential features of the current design are 40 sectors, 2 cm diameter opening for beam in forward direction.
  • Need a way to align HDGeant and Tim’s/Chuck’s (I-DEAS???) drawings
  • Need to establish an authority for changing the geometry of the target. Some start counter design considerations might depend on the possibility of changing target geometry choices.

Probably the easiest way to keep things in alignment would be if Werner could interface with both Tim/Chuck (on the I-Deas??? side) and Sascha S. (on the HDDS side).

Target Status

rory at jlab yesterday, discussion about target organizanal remains a jlab project, cryogenic capability umass play role in organization and oversight perhaps slow controls a lot of stuff to be developed for control software solid targets, interest in gluex, especially for calibration physically remove cryotarget, put in solid target ladder in situ, downstream not attractive for gluex because of extra material in beamline (from discussion in spring) 8 hour change-over time from cryo to solid umass would build the ladder for solid target roster of target materials to be decided, input from gluex for calibration purposes if cryotarget comes out, there is room for planning perhaps a target wheel perhaps motion in z single foil at detector center question from Rory: how much depends on absolute cross sections, what is level? primex shoots for 0.1% writing an mou target mentioned David: calibration channels for solid target? Rory: calibration target for tracking target group at jlab: they will make the target, cryogenic system, target cells will be made in a Christo-like fashion refrigerator: buy stand-alone, decoupled from the magnet. not that expensive. diameter: 2cm? for primex might be fatter, want photons exiting downstream cell wall may have more than one cell aram fleeing to canada to avoid the draft hall d target: postdoc to be hired at umass

discussion with Sasha read into minutes by Mark

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