RE: uniform field region

["Guangliang Yang" <y.guangliang@physics.gla.ac.uk>]

Dear Jim,

   I agree with you that the specification for the field uniformity should
be changed. The old specification is based on the specification for the
Mainz tagger which was operated 1 T ( which means it is much easier to get
high field uniformity). We should make the specification based on our
calculation. About your drawing, I think we should increase the hatched
region beyond the 12 GeV electron trajectory by several centimeters, because
we also need a uniform field for the main beam.  

Cheers

Yang
 

-----Original Message-----
From: owner-halld-tagger@jlab.org [mailto:owner-halld-tagger@jlab.org] On
Behalf Of Jim Stewart
Sent: 17 February 2009 20:24
To: tagger list
Subject: uniform field region

Hello Yang, Franz, and Co.

I am trying to think how to summarize our specification on the field
uniformity in the clearest most general way. I propose making a drawing like
what is attached, and then specifying that for any two points inside the
hatched area that are less than 100 mm apart the difference in field must be
less than 3 parts in 10^4, and that the uniformity over the whole hatched
region must be better than 1%.

If I go in from the pole by 70mm my uniformity is only 3 parts in 10^4 and
not 1 part in 10^4. Do other people agree with this? How far in from the
effective field boundary should we go and what uniformity does this
correspond to ?

Jim