Email from Roger:

From carlini@jlab.org Fri Sep 17 10:56:07 2004
Date: Fri, 10 Sep 2004 01:10:26 -0400
From: Roger Carlini 
To: finn@physics.wm.edu, 'Neven Simicevic' ,
     'Jim Birchall' ,
     'Dave Mack' , 'Juliette Mammei' ,
     'Klaus Grimm' , armd@jlab.org, 'Mark Pitt' ,
     'Allena Opper' , 'Greg Smith' ,
     'Norman Morgan' , 'Mike Finn' ,
     'Yongguang Liang' ,
     'Shelley Page' ,
     'Tony Forest' 
Cc: carlini@jlab.org
Subject: Qweak- Collimator Working Group

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Hi Folks:

Below is a brief summary of my understanding of where we stand and what
folks agreed to do in the next couple of weeks. Please let me know if I left
something out.

1)  Neven^Òs ^Ónew^Ô collimator location would be adopted pending concurrence
from the mini-torus group. Functionally this just moves a single ^Óthin^Ô Cu-Pb
collimator to a location about 3 m from the target. The GEM^Òs and mini-torus
are now upstream of the acceptance defining collimator, but still located
near their previous positions relative to the target and are downstream of
non-acceptance defining Pb shielding (a.k.a. the target region clean up collimator).

2)  An estimate of the maximum shift in average Q**2 due to an energized
mini-torus would be made.

3)  The simulation groups agreed to implement Rick Jones^Ò code modifications
to include internal radiative effects and proper event weighting, add a beam
transport line limiting aperture just downstream of the target, check that
all materials in the simulations are in place and enabled in the code,
and update the reference code libraries accordingly.

4)  The simulation groups would then find the optimum collimator design(s)
to achieve the best FOM^Òs for average Q**2^Òs of  ~0.025 and ~0.035 with
~1.070 GeV and ~1.170 GeV incident beam energies. These solutions might,
but need not use the same collimator. The image length would be constrained
to fit within ~2.1 m. The required bar width would be determined.
We might gain a slight width reduction from the bar rotation.
We would keep a safety margin in selecting the final bar width.

5)  The simulation groups would verify that the bar edge is safely
separated from inelastic electrons generated via pion production processes.

6)  The mini-torus will likely be in a very high radiation environment
and may need to be Rad hardened. Specifically, no epoxy or other organic
materials. The mini-torus P.S. may require some supplementary ripple filtering
and field stabilization. QTOR will require field regulation. Specifications
need to be quantified.

7)  Aggressive options such as V shaped bars and overlapping image
concepts would be abandoned for now.