sPHENIX discussion of the superconducting solenoid

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

Hi,

This morning, we disconnected the braids, then we hipoted on the 1008B side (water-cooled buses and dump resistor).

And "surprinsgly" (at that time at least), the hipot went successfully at 520 V (and we stayed at least for a minute).

Then, we went to the top platform of 1008-IR and we did a hipot.  Surely enough, it failed after it was higher

than 420 V or so.  This indicated something wrong on the magnet side (that we couldn't believe it !).

We tried again to move apart the heater cable (connected to the Gas-cooled/Current Leads) etc.  And we did hipot again slowly and the highest we went was ~460V.  And then we started talking with the Cryo group

(Roberto).  Originally, the dialogue was about those heater cable but soon, we asked about the Vacuum

situation.  Roberto saw 1 gauge at E-1 leavel and another at E-5 ... but the vacuum pump has not been running for some time. 

Soon, the Cryo group staff came and started the pumping when we just tried to disconnect two voltage tap

cables on the platform just to make sure (which we didn't think but just to make sure).  Just after a couple

minutes' pumping, we went to 505 V --- the highest that we have gone this week ! 

So, we put back the voltage tap cables and we waited for half an hour.  Voila, after that, we went to 520 V

without any problem.    I attach a picture of success at 520 V !   ( You  don't know how happy we were

when we reached this value ... after >10 failures this week. )

So, we'd like to ask the Cryo group to keep the pump working from now on.

Kin

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