[Bubble] Reminder: Bubble Chamber Phone Meeting - Wednesday October 7, 3:30 - 5:00 pm, TL 2221

[Jay Benesch]

The spreadsheet attached contains the data carefully taken by Yan and 
Alicia last night, steering through the better-shielded 2D line.  Fudge 
factors of 0.95 for 0L02-7 and 0.96 for 0L02-8 make the expected BdL for 
momentum derived from GSET values consistent with the actual MDL0L03
values at the 0.2% level.  The fudge factors were arrived at by 
eyeballing mean and standard deviation.  I will try to figure out how to 
do two-parameter OLS on the data to refine fudges and get an error 
estimate.

Mike Tiefenback has often raised a concern about discrepancies between 
the gradients reported by the diode readbacks in RFCMs, GMES, and the 
GSET value translation into cavity input.  The fudge factors have to 
increase by about 1% to get the means and standard deviations of the 
GMES-derived momenta near zero.  Since we input GSET, that's what I 
chose to use in eyeballing fudge factors.

Applying these fudge factors to the data taken 8/20 before additional 
shielding was added to 2D line suggests a shift of about 140G.  This is 
about 80% of the value one gets if one takes Joe Grames's number for the 
PEPPo line, which had no shielding, and multiplies by 2D steel shield 
length.  Since the 2D line had mu metal shielding before the steel was 
added, the smaller shift isn't surprising.

I'd like to repeat the 5D segment of
http://opsweb.acc.jlab.org/CSUEApps/atlis/atlis.php?load=Task&task_id=15445
as soon as the line can be put into a state which allows it.  Launch 
steering during the 8/20 run was not done as carefully as last night.

Jay
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