Email from Roger about Jim's Boston collimator redesign studies:

From carlini@jlab.org Thu Sep  2 07:26:12 2004
Date: Wed, 01 Sep 2004 23:04:49 -0400
From: Roger Carlini 
To: Jim Birchall 
Cc: Dave Mack , Juliette Mammei ,
     Klaus Grimm , Mark Pitt ,
     Neven Simicevic , Greg Smith ,
     Norman Morgan , Mike Finn ,
     David Armstrong , Yongguang Liang ,
     Allena Opper ,
     Shelley Page , Tony Forest 
Subject: Collimiator Comments

Hi Jim:

Nice job of summarizing your collimator studies. A few observations:

1)  Even after we select the final collimator dimensions the Q**2 acceptance can be shifted by decreasing the beam 
energy (~150 MeV) if the "selected" collimator is designed for the high end of the acceptable range.

2)  We can also build a collimator with precision bolt on inserts to decrease the theta (top and/or bottom) and phi 
acceptance. We would then be able to select the production running average Q**2 acceptance on-the-fly.

3) I believe some of the image shape distortions seen may be improvable by tweaking the magnet field to fine tune the 
focus for a given collimator setup.

4)  Finally, looks like we gain really fast if we increase phi. The bar widths shown assume straight bars. It might be 
useful to look at increasing the phi (even more than you did) and using longer V shaped or curved detectors. It would be 
useful to see what the ultimate limit might be. Curving the bars also helps to keep the in-elastics stuff out of our 
acceptance.


Best Regards

Roger