sPHENIX discussion of the superconducting solenoid

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

Hi,

 

This morning, after we filled out a few forms so that I get a red TLD can escort Dan Sullivan and Peter Galioto to Bldg. 912 to do a hipot.

 

Long story short, the -ve Current Lead (B) seems to pass the hipot with flying color, nominally 0 micro-amp (the testing report says: max. ~0.3 micro-amp).

The hipot was done at 520 V.

 

But the +Current Lead (A) failed.  We set it at 10 micro-amp  but it failed immediately, or quickly at 20 V, 50 V or 70 V … (even a very slow rate … 300 s for 0 to 520 V).

Even with a Fluke meter, we sometimes measured 60-80 kOhm (between lead and ground) in the morning but sometimes, it’s

“open” (maximum resistance of that meter).   Dan and Peter tried  to poke around and took off the heater on the +ve lead … and looked at those wires underneath

the chimney.

 

Ken Riker and Dan Martin had some ideas and they re-wrapped the MLI (around the ceramic break or so) around noon.

 

At 1:30 pm, we tried again.  The Fluke meter said that the resistance is maximum (open) between +lead and ground  but the hipot failed again.  We tried to

separate those wires hanging from the chimney again and tried again.  The last time, it went to 90 V and had an “arc failure”.

 

Then, we measured it again and we saw “10 kOhm” . ….  Half an hour later when Ken Riker and his colleagues tried to measure again, the resistance was “OPEN” again.

Something was “intermediate” ….coming and going …

 

I talked to Carl and Carl talked with us (Piyush, Dan and myself).   There is no obvious solution.   Carl will come to take a look next week.

 

Piyush said he might have time to take a look at 11 am tomorrow.

 

Let me be dramatic … this is sort of a crisis.   Without solving this problem, we don’t have a magnet ☹

 

Kin