From jmichaelfinn@cox.net Thu Sep  9 07:35:25 2004
Date: Wed, 08 Sep 2004 17:31:14 -0400
From: John M. Finn 
Reply-To: finn@physics.wm.edu
To: carlini@jlab.org
Cc: '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' 
Subject: RE: Qweak working group - next meeting

Dear Roger,

I guess we will have to agree to disagree, pending 3-d views of the
acceptance.

If you want to increase the phi acceptance, then you should consider
attacking the problem at its roots. The problem with defocusing occurs due
to edge focusing at large theta angles, which now exit from the top of the
magnet, instead of the exit face. No edge defocusing = large phi angles.
This edge focusing can have been reduced or eliminated by 1) reducing the
angle of incidence (increasing the focal length and softening the focus) or
2) by rotating the back of the coils outwards, to a more favorable grazing
angle, which will make better use of the magnetic volume. The first requires
a detailed optics optimization, and a willingness to reconsider the
positions of all elements along the beam line. The second requires a change
request in the support structure, which depends on how close they are to
finalizing he bid package.


Regards,
Mike