Announcement of 10/14/04 Teleconference:
Date: Wed, 13 Oct 2004 09:28:31 -0400 (EDT)
From: Mark Pitt
To: Roger Carlini
Cc: Jim Birchall , Juliette Mammei ,
Klaus Grimm , Neven Simicevic ,
Greg Smith , Allena Opper ,
Tony Forest , Norman Morgan ,
Mike Finn , David Armstrong ,
Yongguang Liang , Shelley Page ,
Dave Mack , Richard Jones
Subject: Qweak working group - meeting tommorrow
Hello group,
This is a reminder that we will have a teleconference for our "Qweak
primary collimator working group" tommorrow at:
Thursday October 14 at 4:00 - 5:30 PM Eastern time
Calling instructions are below. Materials will be posted as usual at:
http://www.phys.vt.edu/~pitt/qweak_wg
Appended below are some brief minutes of the last meeting for those who
could not attend. I know that the people who agreed to work on various
issues last time have made progress, so we will certainly hear reports on
these topics:
1. Neven's simulation of light transport in Roger's v-shaped detector
2. Jim's results on v-shaped detector for the 10-8-22 Boston collimator
3. Juliette's results on v-shaped detectors at different z locations
(Juliette's results are already posted at:
http://www.phys.vt.edu/~jmammei/primary_collimator.html
if you want to take a look beforehand; particularly take a look at Table 4
which gives a survey of results for different detector sizes, B field
strengths, and z locations)
Also, Dave Mack has pointed out that the jeopardy proposal deadline is
very close. He is proposing that we try to pick a "reference design" this
week and adopt it at least for the purposes of the proposal. That would
give adequate time to generate proper rates and figures needed for the
proposal. I don't think we are in a position this week to pick the "final
design" but that process could continue a little longer till we are
convinced that we have an optimum detector/collimator design for our fixed
magnet configuration. I think we probably could pick a reference design
with a downstream "unsculpted" collimator and v-shaped detector that would
achieve our FOM and inelastic/elastic goals. I just mention this so
people can think about the strategy, and we'll try to leave plenty of time
for discussion of it tommorrow.
Mark
Calling instructions:
Time: Thursday Oct. 14, 4:00 - 5:30 PM Eastern time
Domestic Dial In Number: (800) 377-8846
Canada Dial In Number: (888) 276-7715
International Dial In Number (302) 709-8424
PARTICIPANT CODE: 08935091
Brief minutes of Thursday October 7 teleconference
1. Jim showed results for v-shaped detector cuts for the Boston 10-8-22
collimator. If I understood correctly, the slope was just on the top of
the bar, so it wasn't like Roger's v-shaped detector. Jim estimated that
the width of the bars he was considering was about 20 cm. These results
lead to a FOM of 0.52, which would give us our desired error on Qweak in
2550 hours at 85% beam polarization.
ACTION ITEM: Jim will consider the FOM, etc. for a true v-shaped detector.
(done, see Jim's email to the group)
2. Juliette showed some initial results for v-shaped detectors. Much of
the discussion was focused on why Juliette was seeing no "goatee" whereas
Neven and Jim do. After the meeting it was determined that Juliette was
not using Willie Falk's field map. Tony has installed that map in CVS
now, so it should be the standard that everybody uses.
ACTION ITEM: Juliette will start to consider v-shaped detectors at various
z locations (and perhaps various magnetic field strengths). It was
realized at the meeting that our current z location is probably not
optimum for a v-shaped detector.
3. Yongguang showed results from trying to "sculpt" the hole in the
detector shielding wall to get rid of inelastics. It appeared that doing
that actually made things worse because of scattering on the collimator
edges. Also, it was realized at the meeting that the reported differences
between Yongguang's rates and Juliette's rates were because Yongguang was
using the "original" Neven downstream collimator, whereas Juliette was
using a Neven collimator with an extended theta range.
4. Neven reported on encouraging results of light transport in a "house"
shaped detector (sloped edges on top but flat at the bottom). He wanted
it flat at the bottom to catch the "goatee". It was realized at the
meeting that we probably could tune the magnetic field or z location to
get rid of the goatee and there use a v-shaped detector like Roger has
proposed with sloped edges that are parallel to each other.
ACTION ITEM: Neven agreed to simulate a "Roger style" v-shaped detector.
(done) And he agreed to consider light transport with a more realistic
distribution of input rays corresponding to the extreme angles expected at
the edge of the bars.
That was the main points I took notes on; if I missed anything please send
corrections to this list.
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Mark Pitt
Department of Physics
Virginia Tech
Robeson Hall
Blacksburg, VA 24061-0435
Phone: (540) 231-3015
Fax: (540) 231-7511
e-mail: pitt@vt.edu
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