sPHENIX discussion of the superconducting solenoid

["Yip, Kin" <kinyip AT bnl.gov>]

Agenda/powerpoint/pdf :  https://indico.bnl.gov/conferenceDisplay.py?confId=3695

 

1.      Status :
-- I mentioned that the magnet cryostat readjustment was done successfully on Oct. 3, 2017.
-- We’re now literally waiting for the C-AD carpenters to come back to finish the handrails on the platform.  In principle, we just left with
one day’s carpentry work.  But the carpenters were told to go to STAR on Tue. and LeReC on Wed.  People in the meeting were all dissatisfied
with the situation.

2.      Carl Schultheiss advised us to arrange rigging next Friday (Oct. 20) for his rack to be shipped to Bldg. 912 in the test site.  I’ve sent email to Dave Phillips
and Jim Mills even suggested to arrange for a couple days next week (not just Friday, as if it didn’t happen, it’d be further skipped to the week after).

3.      Cable trays are continued to be laid out by M. Rau and his colleagues (PHENIX electricians) this week.   Carl and PK Feng design the route of the signals cables
to go from Cryo Rack => to the top of the platform along the M. Rau’s cable tray already built => across the platform and then down using “basket” tray to
Carl’s data-acquisition rack.

4.      Jim Mills reminded us to check once more (walkthrough) before we close the magnet.   Brian van Kuik even suggested that we put up a sign to remind ourselves
to check it.

 

5.      I mentioned that the Cryo plant in 912 didn’t seem to be working.  Paul Orfin explained a bit to us and the Cryo group is trying to fix the problem that the plant didn’t generate as much He as it has been.

 

6.      Hopefully, the carpenters will work overtime for us on our platform.  Tomorrow morning at 9 am, I’ll meet with Dave Phillips to assess the situation to decide when we’ll
install the Valvebox --- which looks more like Friday as Dave believed.

 

7.      The last topic is about the “Magnetic Field Effect on the Performance of TPC” mainly a talk given by Garg Prakhar.  The original motivation of the analysis is to see whether
sPHENIX (such as TPC) needs to do magnetic field map   or  we can just use the field map from software (Opera).  Last week, before the meeting, Prakhar showed us
some analysis of his which showed an awkward kink in Bx at R=30 cm.   I checked and saw Bx at Y=30 cm (X=0) myself.   After I told Wuzheng Meng, he made two
different efforts (making the grid finer and the volume inside the Steel quadrilateral) which seemed to solve the problem.   Garg took the field map from me and did his analysis again to show the improve picture.

In the meeting, people accepted that Bx/By will never be ~0.  They’d give 30 micron or even > 100 micron of electron displacement on the TPC pad but the distribution
of the displacement seems very flat.   It seems that the deviation from the average displacement is in the order of magnitude of 10 micron, which is to be compared with
the TPC’s position rms of ~100 to 200 microns.  At the end of the meeting, Prof. Hemmick seems to convince us that the uniformity is good enough and it’s the misalignment of the TPC which would cause more problem.    Prof. Hemmick has devised a scheme to align TPC with respect to the Magnet in the final installation.

 

[ John Haggerty informed us that his magnetic probe is like $700 each. ]

 

 

Kin