Difference between revisions of "GlueX TOF Meeting, September 15, 2011"

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* '''JLab''': Chuck Hutton, Mark Ito (chair), Simon Taylor, Tim Whitlatch, Beni Zihlmann
 
* '''JLab''': Chuck Hutton, Mark Ito (chair), Simon Taylor, Tim Whitlatch, Beni Zihlmann
  
−
=Announcements=
+
==Announcements==
  
 
We talked about the meeting with Hamamatsu representatives scheduled for tomorrow here at JLab, mainly to discuss SiPM's. Paul has been talking to Andrew Allen of Hamamatsu who will be there and asked him some of the questions on current limits that we have been discussing. Beni and Mark will meet with the visitors over lunch to discuss these issues as well.
 
We talked about the meeting with Hamamatsu representatives scheduled for tomorrow here at JLab, mainly to discuss SiPM's. Paul has been talking to Andrew Allen of Hamamatsu who will be there and asked him some of the questions on current limits that we have been discussing. Beni and Mark will meet with the visitors over lunch to discuss these issues as well.
  
 +
==Rreview of minutes from last meeting==
  
 +
We went over the [[GlueX TOF Meeting, September 1, 2011#Minutes|minutes from the September 1st meeting]].
  
−
have magnetic shield extend beyond photocathode
+
* Mark will circulate a new draft of the scintillator specifications this afternoon.
−
since we have a large enought order that should not be problem
+
−
mechanically simple
+
−
butt up against crystal
+
  
−
still a couple of gauss where the mu metal started
+
==Detector dimensions, light guide dimensions==
  
−
detector dimentions, light guide dimensions
+
We discussed many of the issues that have been raised over the past few weeks. Chuck provided a [https://halldweb1.jlab.org/talks/2011-3Q/TOF%209_15_11.pptx set of drawings] of the current design to guide discussion.
  
−
machining straight piece before add 1cm straight
+
* Andrew Allen mentioned to Paul that we may be able to get the μ-metal shield extended beyond the photocathode, given the quantity we are ordering. Andrew is looking into it.
−
  or extend and reduce radius of curvature
+
** Tim said there was still a couple of Gauss at the photocathode with the off-the-shelf dimensions.
 +
* We decided to have a 1 cm straight section of the light guide where it joins to the scintillator. This helps with the non-square problem (see below) That way we can support both sides of the glue joint.
 +
** If this new straight section is made too long, then the light guide cannot be machined out of the currently used lucite cylinder.
 +
* Tim reported that there are constraints on the geometry from the FCAL and the FCAL support structure. If the light guides could be made shorter, or be bent less, that would help.
 +
** Paul remarked the the in-board edge of the iron sleeve can be trimmed (corner cut off) to help with the interference between neighboring PMT's.
 +
** Tim reported that the iron shielding can be obained with a smaller diameter and still accept the PMT's.
 +
* Non-square problem: when the thickness of wrapping is included the array is no longer square and the ends of the scintillator would be inside the outside edge of the scintillators of the other plane. We will make the scintillator a bit longer (from 252 cm to 254 cm or so) to avoid this as well as adding a straight section to the light guides.
 +
* Paul raised the possibility of needing extra Tedlar wrapping, beyond the current design, to insure a good light shield around the VM2000 wrapping should it be necessary to buy the VM2000 in small sheets. If that is the case the VM2000 would be in sections butted up against each other and each joint would constitute a thin spot in the light-tight-ening. The extra layer of Tedlar changes the total thickness of wrapping from 1.34 cm to 1.79 cm. We thought that an external layer on the upstream and downstream faces might suffice and avoid another Tedlar around each counter.
 +
* We decided on a 3 mm gap between planes of the TOF to reduce stress on the mechanical design process.
 +
* There is 2 cm between the TOF and FCAL presently. Tim suggested we open that up to 3 cm or so.
  
−
constraints from support, fcal
+
Tim and Chuck will work on a optimization of these parameters and of the light guide shape and send around a proposal. Tentatively we will have a special meeting, this Thursday at 9 am, with the mechanical folks at FSU to discuss the proposal.
−
 
+
−
perhaps can trim in-board edge of iron cylinder
+
−
 
+
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9 am thursday
+
−
 
+
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make paddles a little longer
+
−
 
+
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1.34 cm goes to 1.79 cm if double wrap of tedlar
+
−
 
+
−
3 mm gap between planes
+
−
 
+
−
tof and fcal face, there is 2 cm right now
+
−
would like more space go to 3 cm
+
  
 
tof schedule
 
tof schedule

Revision as of 15:25, 15 September 2011

Location, Time

Thursday, September 15, 2011
10:00 am EDT
JLab: CEBAF Center, Room F326

Agenda

  1. Announcements
  2. Minutes from the last meeting
  3. Prototype Status
    • Detector dimensions, light guide dimensions
    • PMT base design, rates, currents, amplification
    • Attempts to improve timing resolution [1]
  4. Contract Status


Communication

Videoconference

  1. ESNet: 8542553
  2. EVO: EVO site

Telephone

  1. dial:
  2. enter access code followed by the # sign: 3421244#

Slides

Talks can be deposited in the directory /group/halld/www/halldweb1/html/talks/2011-3Q on the JLab CUE. This directory is accessible from the web at https://halldweb1.jlab.org/talks/2011-3Q/ .

Minutes

Present:

  • FSU: Paul Eugenio, Sasha Ostrovidov
  • JLab: Chuck Hutton, Mark Ito (chair), Simon Taylor, Tim Whitlatch, Beni Zihlmann

Announcements

We talked about the meeting with Hamamatsu representatives scheduled for tomorrow here at JLab, mainly to discuss SiPM's. Paul has been talking to Andrew Allen of Hamamatsu who will be there and asked him some of the questions on current limits that we have been discussing. Beni and Mark will meet with the visitors over lunch to discuss these issues as well.

Rreview of minutes from last meeting

We went over the minutes from the September 1st meeting.

  • Mark will circulate a new draft of the scintillator specifications this afternoon.

Detector dimensions, light guide dimensions

We discussed many of the issues that have been raised over the past few weeks. Chuck provided a set of drawings of the current design to guide discussion.

  • Andrew Allen mentioned to Paul that we may be able to get the μ-metal shield extended beyond the photocathode, given the quantity we are ordering. Andrew is looking into it.
    • Tim said there was still a couple of Gauss at the photocathode with the off-the-shelf dimensions.
  • We decided to have a 1 cm straight section of the light guide where it joins to the scintillator. This helps with the non-square problem (see below) That way we can support both sides of the glue joint.
    • If this new straight section is made too long, then the light guide cannot be machined out of the currently used lucite cylinder.
  • Tim reported that there are constraints on the geometry from the FCAL and the FCAL support structure. If the light guides could be made shorter, or be bent less, that would help.
    • Paul remarked the the in-board edge of the iron sleeve can be trimmed (corner cut off) to help with the interference between neighboring PMT's.
    • Tim reported that the iron shielding can be obained with a smaller diameter and still accept the PMT's.
  • Non-square problem: when the thickness of wrapping is included the array is no longer square and the ends of the scintillator would be inside the outside edge of the scintillators of the other plane. We will make the scintillator a bit longer (from 252 cm to 254 cm or so) to avoid this as well as adding a straight section to the light guides.
  • Paul raised the possibility of needing extra Tedlar wrapping, beyond the current design, to insure a good light shield around the VM2000 wrapping should it be necessary to buy the VM2000 in small sheets. If that is the case the VM2000 would be in sections butted up against each other and each joint would constitute a thin spot in the light-tight-ening. The extra layer of Tedlar changes the total thickness of wrapping from 1.34 cm to 1.79 cm. We thought that an external layer on the upstream and downstream faces might suffice and avoid another Tedlar around each counter.
  • We decided on a 3 mm gap between planes of the TOF to reduce stress on the mechanical design process.
  • There is 2 cm between the TOF and FCAL presently. Tim suggested we open that up to 3 cm or so.

Tim and Chuck will work on a optimization of these parameters and of the light guide shape and send around a proposal. Tentatively we will have a special meeting, this Thursday at 9 am, with the mechanical folks at FSU to discuss the proposal.

tof schedule

pmt procured in two weeks support structure, buy in spring by next may testing scintillators and light guides procure scint. nov. 2

may have to change divider to optimize for lower gain and add amplifier 10^8 vs. 10^7 contradiction between drawing and spec sheep sasha seeing 160 uA already with cosmics


sasha presentation mystery with trigger counter

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