Difference between revisions of "GlueX TOF Meeting, October 13, 2011"

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(tubes, stages, rates, proposals)
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* '''FSU''': Paul Eugenio, Sasha Ostovidov
 
* '''FSU''': Paul Eugenio, Sasha Ostovidov
 
* '''JLab''': Mark Ito (chair), Elton Smith, Simon Taylor, Beni Zihlmann
 
* '''JLab''': Mark Ito (chair), Elton Smith, Simon Taylor, Beni Zihlmann
 +
 +
==Mechanical Design==
 +
 +
Chuck Hutton and Ian Winger have had difficulty getting together to discuss changes to the light guides. Chuck should try and give Ian a call next week after he (Chuck) returns from vacation.
 +
 +
==PMT base design, rates, currents, amplification==
 +
 +
We discussed several issues around handling the high-rate counters in the TOF array.
 +
 +
* Paul pointed out that there a lot of uncertainties that make it hard to plan. We do not have firm numbers from Hamamatsu on tube lifetime and the rate calculations are only estimates.
 +
* Elton said that the uncertainties are large, but are "only" about a factor of 2 or so whereas the current estimates are too high by a factor of 20 or more. Moreover, rate estimates from Monte Carlo tend to underestimate the reality.
 +
* Elton mentioned that if we decide on a plan where tubes have to be replaced, we should consider not gluing them to the light guides.
 +
* If we have to run at reduced tube gain then it makes sense to do so with a lower gain tube, rather than reducing the HV on a high gain tube, i. e., we should consider the 8-stage Hamamatsu tube (H10570).
 +
* At a photon flux of 10<sup>7</sup>/s the problem is obviously much less that at 10<sup>8</sup>/s. We could consider some sort of two stage plan.
 +
* Beni proposed doing a study with a lower gain, corresponding the the 8-stage tube at a level that produces acceptable lifetime, to see if there is an efficiency issue with hits from the far end of the counter if amplifiers are not used.
 +
* Paul has two of the 8-stage tubes. He and Sasha will take a look at them and compare to the performance of the 10-stage tubes they have been focusing on.
 +
* The consensus proposal, given our current understanding, is to buy 8-stage tubes for the high-rate counters and stay with 10-stage tube. If possible we will run at 10<sup>7</sup>/s without amplifiers on the high-rate counters and design an amplification scheme for use at 10<sup>8</sup>/s.

Revision as of 14:18, 13 October 2011

Thursday, October 13, 2011
10:00 am EDT
JLab: CEBAF Center, Room F326

Agenda

  1. Announcements
  2. Minutes from the last meeting
  3. Mechanical design: Tim
  4. PMT base design, rates, currents, amplification Beni
  5. Prototype status: Paul, Sasha [1]
  6. Contract Status: Mark

Communication

Videoconference

  1. ESNet: 8542553
  2. EVO: EVO site

Slides

Talks can be deposited in the directory /group/halld/www/halldweb1/html/talks/2011-4Q on the JLab CUE. This directory is accessible from the web at https://halldweb1.jlab.org/talks/2011-4Q/ .

Minutes

Present:

  • FSU: Paul Eugenio, Sasha Ostovidov
  • JLab: Mark Ito (chair), Elton Smith, Simon Taylor, Beni Zihlmann

Mechanical Design

Chuck Hutton and Ian Winger have had difficulty getting together to discuss changes to the light guides. Chuck should try and give Ian a call next week after he (Chuck) returns from vacation.

PMT base design, rates, currents, amplification

We discussed several issues around handling the high-rate counters in the TOF array.

  • Paul pointed out that there a lot of uncertainties that make it hard to plan. We do not have firm numbers from Hamamatsu on tube lifetime and the rate calculations are only estimates.
  • Elton said that the uncertainties are large, but are "only" about a factor of 2 or so whereas the current estimates are too high by a factor of 20 or more. Moreover, rate estimates from Monte Carlo tend to underestimate the reality.
  • Elton mentioned that if we decide on a plan where tubes have to be replaced, we should consider not gluing them to the light guides.
  • If we have to run at reduced tube gain then it makes sense to do so with a lower gain tube, rather than reducing the HV on a high gain tube, i. e., we should consider the 8-stage Hamamatsu tube (H10570).
  • At a photon flux of 107/s the problem is obviously much less that at 108/s. We could consider some sort of two stage plan.
  • Beni proposed doing a study with a lower gain, corresponding the the 8-stage tube at a level that produces acceptable lifetime, to see if there is an efficiency issue with hits from the far end of the counter if amplifiers are not used.
  • Paul has two of the 8-stage tubes. He and Sasha will take a look at them and compare to the performance of the 10-stage tubes they have been focusing on.
  • The consensus proposal, given our current understanding, is to buy 8-stage tubes for the high-rate counters and stay with 10-stage tube. If possible we will run at 107/s without amplifiers on the high-rate counters and design an amplification scheme for use at 108/s.