[Halld-tracking-hw] drift chamber positions inside Bcal

[Elton Smith]

Hi everyone,

I wanted to bring up a discussion, which you all have probably all 
thought about, and perhaps agreed on. As we are in the process of 
installing the Bcal into the solenoid, we note that its position inside 
the magnet will not be "ideal", even as the insertion is going very 
well. (By ruler, the Bcal appears to be about 1/8" low and approximately 
centered north-south). Tim reminded me that after insertion, the Bcal 
will be surveyed and the rails for the drift chambers will be mounted 
according to "as built" locations.  But we need to decide whether the 
rails should be centered on the Bcal or the magnet. A related question 
is where to position the target. My first thought is that these 
detectors should be located relative to the actual Bcal position. Note, 
however, that this may mean the axis is not perfectly along the z-axis 
(defined by the solenoid).

Comments/suggestions? We need to make this decision over the next couple 
of days.

Cheers, Elton.





-- 
Elton Smith
Jefferson Lab MS 12H5
12000 Jefferson Ave STE 16
Newport News, VA 23606
(757) 269-7625
(757) 269-6331 fax