From: Geary Eppley (eppley_at_physics.rice.edu)
Date: Tue Mar 25 2003 - 11:11:58 EST
Hi Huan,
Maybe you could reconsider the paragraph about TOFr HV tripping before
sending it out or before I forward it to the full TOF list.
The TOFr HV tripping is
a major technical problem that needs to be solved. Neither of the possible
causes that we can think of has a good consequence. If the CAEN unit is
failing, we need to re-think our reliance on CAEN to provide the HV. If
the tray itself is developing this high current, it may take us a long
time to find the point inside the tray where the current occurs and
to devise a solution to prevent HV failure in 120 trays.
So we need to find the cause of the problem and a solution to make the
project technically sound. Saying that we need to find the cause to be
able to answer the questions of shift leaders and others sounds silly and
frivolous to me and is not the public image the TOF group wants to
project. I think we would rather try to preserve what I think is our
reputation as a technically competent group.
Everyone is already aware that it may be an HV supply problem.
A test to help determine the cause of this problem was proposed on the
TOFp mail list Sunday morning. We are going to swap HVA+ with HVB+ to see
if the problem follows the supply. Since you are on the TOFp email list,
it doesn't seem necessary for you to suggest that we look for a test since
you should already have been informed of the test we propose to do.
If you have comments on this particular test or other tests to propose,
that would be a constructive comment.
Regards,
Geary
---------- Forwarded message ----------
Date: Mon, 24 Mar 2003 14:15:29 -0800
From: Huan Z. Huang <huang_at_physics.ucla.edu>
To: eppley_at_physics.rice.edu
Subject: FW: Mail delivery failed: returning message to sender
Geary,
Please forward this email to the startof-hn list. I seem to have
problem to send to the list.
Thanks.
Huan
Hello All,
There is a strong physics proposal prepared by Zhangbu and his students
to do a TOFr dedicated data-taking for 2M p+p events. Other than the
exciting physics in the identified particle spectra from p+p collisions,
the TOFr data will also help us understand the pile-up problem in the
TPC when we run p+p at high luminosity.
We should re-visit the issue of pVPD high voltage. As we understood from
the previous discussions, if we can run the pVPD at a high PMT voltage,
we can improve the pVPD single hit resolution. This may be a very useful
improvement for p+p running. I would suggest that one of
Frank/Geary/Bill and Zhangbu to work out a plan to switch the HV power
supply for pVPD.
Regarding the TOFr HV trips, from the email info from Frank et al. it
does appear to me that it may not be an issue related to the TOFr. It
may very well be the HV supply problem. Do we have a list of diag tests
that will allow us to establish the fact? Because many shift leaders
were aware of the trips, I am sure that people will ask for an
explanation. It will be useful if we have a good understanding of the
problem.
Thanks. Regards,
Huan
Huan Z. Huang
Department of Physics and Astronomy
University of California
Los Angeles, CA 90095-154705
Telephone 310-825-9297
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