[BTeam] new injector solenoid TN

[Jay Benesch]

A new TN summarizing my work on injector solenoids (FA,FD,FG and FL) and 
my proposed replacement for all but the FG is available in
https://jlabdoc.jlab.org/docushare/dsweb/View/Collection-23718
Injector group has previously received a copy.

I still lack drawings and therefore models of the FH, FB and FQ solenoids.

The proposed replacement has one tenth the variation in focusing 
strength across the centered beam versus existing solenoids.  In the 
chopper with beam on 3 cm diameter circle, improvement is a factor of 
four.  Replacement design envelope was dictated by the existing chopper 
vacuum vessel.  Flanges have to be ground off beam pipe to remove 
existing magnets.  The bore of the new design is large enough to 
eliminate this need at six of eight locations (chopper is exception).

Jay