[Hps] ECal position

[Gabriel CHARLES]

That's right!

   When we installed the ECal the first time, the distance between top 
ECal and vacuum chamber, and bottom ECal and vacuum chamber were very 
similar (we moved the calorimeter mm by mm so we could see a 1 mm 
difference), we concluded that it was due to the position of the 
chamber. There may be 1 mm difference between the center of the chamber 
and the "true" center, so it was hard to conclude at that time. The 
calorimeter box could also be 1 mm down, the targets used for the survey 
being independant of the box.

  Anyway, your idea is probably right, could tracking help?

Regards,
  Gabriel

Le 2015-05-06 18:36, Nelson, Timothy Knight a écrit :
> Here are the results of the ECal survey shown in January.  Am I wrong
> that this indicates that the bottom ECal is closer to the beam by 1 -
> 2 mm (and about 1.5 mm in the middle where rates are high) compared to
> the top?  If so, then that could explain the rate effects we see in
> the top vs. bottom ECal, since that’s about 1 mr change in acceptance.
> 
> Tim
> 
> 
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-- 
Gabriel CHARLES
Institut de Physique Nucléaire d'Orsay