sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Hi,

We had a meeting where many experts (P. Joshi, M. Anerella, J. Muratore, S. Plate, R. Ceruti, J. D'ambra, P. Orfin, R. Than and D. Lynch)
gathered and discussed the 75 A test result/analysis on Wed. and the temperature readings of TT1786/TT1787 sensors.
 
Carl Schultheiss' presentation can be found :
https://collab.external.bnl.gov/sites/sPHENIX-Magnet/Past%20Presentations/2018-2-25%2075A%20Test%20Analysis.pptx

In Carl's fit,  we've found approximately 184 nano-Ohm on the -ve (B) side and 41 nano-Ohm on the +ve (A) side.

During the meeting,  most people believed that the temperature readings of the TT1786/TT1787 sensors didn't reflect the real temperature
of the superconductor.    M. Anerella pointed out that the temperature sensors might be reading part of the bulky G10 pieces on top of these
two sensors --- the other two sensors reading 5/6K  didn't have these G10.  The G10 pieces are not in contact with any cooling pipe and
it'd take much longer time to go down in temperature.

And we think that the above resistance are very likely due to the joints, Joe D'ambra told us how he made the joints using Indium.  Though
typically, each should be ~10 nano-Ohm in his experience, he told us that the original surfaces of the joints was rough, in which one side
could be worse than the other.

Probably only Piyush Joshi liked to entertain the small possibility that the extension might not be cold/superconducting.

In any case, we've all agreed to go higher in current (100 A, 200 A ... ) using our real sPHENIX power supply and Piyush suggested measuring
the voltages across the joints at these higher currents.   He even was willing to lend us two more precise meters in addition to the one that
Carl has got, so that we may measure three portions at each time, reducing the no. of times in plugging and unplugging.  

This test (with sPHENIX Power Supply and quench-detector) requires Z. Altinbas, P.  Rosas et. al. in addition to Carl.

Unfortunately, at the time of the meeting, the LHe storage was still ~24% (now it's > 25%), at the rate of <1% per hour re-generation, it
didn't look like we'll have enough LHe to cool down and provide enough meaningful hours for Friday. 

Therefore, we've decided to wait until Monday (as early as possible) to do the above-mentioned test.  This way, we'll start from ~70% LHe storage.

Kin