sPHENIX discussion of the superconducting solenoid

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

https://indico.bnl.gov/event/15340/

 

People attended include: Jim Mills, Tom Tallerico, Brian Van Kuik, Paul Orfin, Roberto Than, Dan Sullivan, Achim Franz, Carl Schultheiss and Kin Yip.

 

1. I showed this powerpoint to describe what happened on Thursday (Mar. 31, 2022) and yesterday (Apr. 5, 2022) :

https://indico.bnl.gov/event/15340/attachments/40420/67577/2022-4-6_sPHENIX_Magnet_Meeting.pptx

 

That the hipot seemed to fail last Thursday with 10 micro-amp threshold with the continuously rising voltage.  But yesterday, with the Stanford meter and manually

increasing the voltage and stopping until the leakage current dropping to 0, we saw only instantaneous leakage current jump (and drop) and the leakage current

has been 0 (with 10 micro-amp sensitivity) at a steady voltage (DC).

 

2. Carl Schultheiss added some details during my presentation. 

 

---- He did take off one Aluminium tape with a bit of Kapton at the end of the chimney, which in principle shouldn’t matter because that Aluminium tape was outside the Kapton anyway (unless there are holes in the Kapton).

---- Also, we tried the best (by taping the groups of wires to the two sides of the table) to keep the wires away from the current leads A and B, at the bottom of the chimney.

 

3. About that 100 micro-amp threshold trial with the Stanford meter, Carl added that the Stanford meter immediately tripped when he set the threshold to 100 micro-amp as the meter tried to go to 10 V by default.  Setting to 1 mA would avoid the problem.   Carl thinks it’s the combination of the capacitance and intrinsic property of the Stanford meter.
   
   
4. The mystery of why we saw 10 to 100 kOhm at times with the Fluke meter on Thursday was still a mystery.   Carl suggested humidity as a possibility.  Dan Sullivan said the humidity was 55% (I think I saw ~45%) last Thursday and that shouldn’t be a problem.   I invented a theory that the charges left in the Current Leads (after we charged it up to higher voltage) might be still flowing when we tried to measure resistance and distorted the resistance measurement, which Carl said was kind of non-sense 😊 ☹   I’ll try to measure the resistance immediately next time after Carl powered off his Stanford meter when we finish the hipot.
   
   
5. But we all agreed to do the hipot again when the Cryo group finishes all the multi-layer-insulation, or restoring the gas-cooled leak connected to the Current Leaks (at the top), or when they re-wrap the heater around the top of the Current Leads.   We’ll also try to hipot again before Ray Ceruti install the restraints.    The restraints are probably in touch with the Current Leads and we may not be able to do the hipot.   But after the restraints can be removed in 1008, we can do the hipot again, before joining the .
   
   
6. I have asked people (such as the Cryo group) to write down what they did with the task on the logbook that I placed in 912 next to the Valvebox.
   
   
7. Accidentally, for one reason or another, when we unwrapped both of the heater shields (~silicon) surrounding the top  of the Current Leads, we found that they were badly burnt --- which should have happened during the high-field test.  Tom Tallerico and Paul Orfin are trying to find a better solution than those silicon-type materials.

 

Kin