Difference between revisions of "Time-of-Flight/Start-Counter/Target Meeting, January 8, 2010"

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=Location, Time=
 
=Location, Time=
  
−
Friday, December 11, 2009<br>
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Friday, January 8, 2010<br>
 
2:00 pm EDT<br>
 
2:00 pm EDT<br>
 
JLab: CEBAF Center, Room F326/7<br>
 
JLab: CEBAF Center, Room F326/7<br>
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[http://evo.caltech.edu EVO]: [http://evo.caltech.edu/evoGate/koala.jnlp?meeting=eueneevlv2aua2avIu direct meeting link]<br>
 
[http://evo.caltech.edu EVO]: [http://evo.caltech.edu/evoGate/koala.jnlp?meeting=eueneevlv2aua2avIu direct meeting link]<br>
 
Conference Group: 800-377-8846, participant code: 77438230<br>
 
Conference Group: 800-377-8846, participant code: 77438230<br>
−
'''Slides''': talks can be deposited in the directory <code>/group/halld/www/halldweb1/html/talks/2009-12</code> 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/2009-12/ .
+
'''Slides''': talks can be deposited in the directory <code>/group/halld/www/halldweb/html/talks/2010-01</code> on the JLab CUE (you have to be a member of the "halld" group). This directory is accessible from the web at https://halldweb.jlab.org/talks/2010-01/ .
  
 
=Agenda=
 
=Agenda=
  
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# [[Time-of-Flight/Start-Counter/Target Meeting, November 13, 2009#Minutes | Minutes from the last meeting]]
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# [[Time-of-Flight/Start-Counter/Target Meeting, December 11, 2009#Minutes | Minutes from the last meeting]]
 
# Time-of-Flight Status: Sasha O.?
 
# Time-of-Flight Status: Sasha O.?
−
# Start Counter Status: Werner?
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# Start Counter Status: Werner? http://markito3.wordpress.com/2009/09/18/targetstart-counter-geometry/
 
# Target Status: Aram?
 
# Target Status: Aram?
 
# [[Time-of-Flight/Start-Counter Action Items|Action Items]]
 
# [[Time-of-Flight/Start-Counter Action Items|Action Items]]
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=Minutes=
 
=Minutes=
  
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'''JLab''': Mark Ito (chair), Chris Keith, Sascha Somov, Simon Taylor, Tim Whitlatch, Beni Zihlmann
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'''FIU''': Werner Boeglin<br>
 +
'''JLab''': Chuck Hutton, Mark Ito (chair), Sascha Somov, Simon Taylor, Elliott Wolin
  
−
=Time-of-Flight=
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==Minutes from the last meeting==
  
−
Sascha asked about whether we intend to use constant fraction or leading edge discriminators for the the TOF. Ben Raydo is working on a 16 channel leading-edge discriminator for Hall B and will build 5 for us as well. Richard Jones is planning to use leading-edge discriminators for both the microscope and the fixed array for the tagger because of the high rates in those counters.
+
We went over [[Time-of-Flight/Start-Counter Meeting, June 12, 2009#Minutes|them]]. Elliott talked to Chris about controls. Chris's concern about programming PLC's is not an issue.
  
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=Target=
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==Start Counter status==
  
−
Chris Keith reported on his thinking about a dedicated refrigerator for the target. He has identified a pulse tube refrigerator, made by [http://www.cryomech.com/ Cryomech], that seems appropriate. It is a mechanical device; it has no cold moving parts and will therefore produce very little vibration. Maintenance is relatively easy; the maintenance cycle is 20,000 hours. It uses helium gas as the working substance and a room temperature compressor. There are two stages of cooling, 50 or 60 Watts to cool the radiation shield, tens of Watts of cooling of the target liquid at 20 K and 1.5 W at 4.5 K. It requires cooling water for the compressor and runs on 220 V 3-phase power. Hydrogen for the target cell would be circulated in a completely closed system; probably several liters will be needed. Chris mentioned that buying a spare compressor might be good idea.
+
Sascha showed [http://halldweb.jlab.org/talks/2010-01/plot_radl_old.pdf before] and [http://halldweb.jlab.org/talks/2010-01/plot_radl_new.pdf after] plots of a radiation scan of the target/start-counter area. These show the amount of material an infinite momentum particle will encounter when launched from the center of the target. Improvement is seen in the start counter component due to a new geometry which starts the bending farther upstream and in the "target" component due to a shortened scattering chamber (end cap moved upstream). See [http://markito3.wordpress.com/2009/09/18/targetstart-counter-geometry/ Mark's notes] on an old version of [http://halldweb.jlab.org/talks/2009-07/SC%20CONE%20DETAIL.pptx Chuck's drawings] for a guide to the geometry.
  
−
The target group will take full responsibility for design and testing of the complete system, with the possible exception of the controls (see below). They will need engineering design authority from Hall D. Steve Christo will probably be consulted on the target cell fabrication. The control system is relatively small: about 10 thermometers, 5 pressure guages and a heater. If a PLC control system is chosen, the target group will not be able to help. If VME-based EPICS is chosen, they can take care of that.
+
Werner gave us an update:
  
−
Chris and his group probably cannot start thinking seriously about our target until Fall 2009. They have a frozen spin target experiment and Qweak coming up. He estimates that our project should take about 18 months. Tim noted that the schedule indicates that the target system should be done by July 2012, so this is a rough match. The total target group consists of three physicists, two engineers and three technicians.
+
* 3 mm scintillator looks OK; seems to give sufficient light
 +
* 350 ps time resolution has been measured with a fine-mesh phototube
 +
* He will try tests with the new SiPM from Hamamatsu
 +
* The SiPM he has in hand has too low a PDE
 +
* Rise time with the fine-mesh PMT is 2 ns
 +
* He has tried wrapping the counters with VM2000[?], a highly reflective material. This really helps light yield.
 +
* He is thinking of a scheme where the wrapping provides optical isolation among the counters, but not necessarily a completely light-tight seal. That could be provided by a global enclosure.
 +
* He is doing measurements with 2 mm scintillator currently.
  
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Tim does not anticipate huge problems with mechanical support. The plan is to follow the scheme used in Hall B.
+
Werner will be travelling to JLab on the 21st and will be available to discuss start counter issues.
−
 
+
−
Chris and Tim thought it was premature to start regular dedicated target meetings. We will therefore continue to include target items in the agenda for this meeting.
+

Latest revision as of 05:07, 1 April 2015

Location, Time

Friday, January 8, 2010
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/halldweb/html/talks/2010-01 on the JLab CUE (you have to be a member of the "halld" group). This directory is accessible from the web at https://halldweb.jlab.org/talks/2010-01/ .

Agenda

  1. Minutes from the last meeting
  2. Time-of-Flight Status: Sasha O.?
  3. Start Counter Status: Werner? http://markito3.wordpress.com/2009/09/18/targetstart-counter-geometry/
  4. Target Status: Aram?
  5. Action Items

Minutes

FIU: Werner Boeglin
JLab: Chuck Hutton, Mark Ito (chair), Sascha Somov, Simon Taylor, Elliott Wolin

Minutes from the last meeting

We went over them. Elliott talked to Chris about controls. Chris's concern about programming PLC's is not an issue.

Start Counter status

Sascha showed before and after plots of a radiation scan of the target/start-counter area. These show the amount of material an infinite momentum particle will encounter when launched from the center of the target. Improvement is seen in the start counter component due to a new geometry which starts the bending farther upstream and in the "target" component due to a shortened scattering chamber (end cap moved upstream). See Mark's notes on an old version of Chuck's drawings for a guide to the geometry.

Werner gave us an update:

  • 3 mm scintillator looks OK; seems to give sufficient light
  • 350 ps time resolution has been measured with a fine-mesh phototube
  • He will try tests with the new SiPM from Hamamatsu
  • The SiPM he has in hand has too low a PDE
  • Rise time with the fine-mesh PMT is 2 ns
  • He has tried wrapping the counters with VM2000[?], a highly reflective material. This really helps light yield.
  • He is thinking of a scheme where the wrapping provides optical isolation among the counters, but not necessarily a completely light-tight seal. That could be provided by a global enclosure.
  • He is doing measurements with 2 mm scintillator currently.

Werner will be travelling to JLab on the 21st and will be available to discuss start counter issues.

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