sPHENIX discussion of the superconducting solenoid

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

Hi,

Our 24-hour run started at about 4:08 pm yesterday.  Today at 4:13 pm, we started the normal ramp-down (slow discharge)

which made use of the freewheeling diode inside the Magnet Power Supply and water-cooled-buses to release energy, mostly not through the dump resistor. 

It took almost an hour (or about 51 minutes) to go from ~4620 to ~1000 A, at that point, we did a fast-discharge (by opening the contactors in the Dump Resistor and the energy was released through the Dump Resistor), so that we don't need to wait for another hour.  The temperature rise for the magnet  temperature is about only 2 K.  I attach 2 plots to show what I've described above.  This is a practice that BaBar did (their literature said fast-discharging at ~1300 A) and we did the same during the high-field test.  We'll do this also in the future sPHENIX operation.

Tomorrow, CAS, Carl and I would try to ramp the magnet at 1.5 A/s once.   If we succeed, we'll go to the top current and Roberto (Cryo) will try to do some small adjustment/tuning for 15 minutes or so at that current.    If we fail, we will end anyway.  ( Roberto can tune more  next week during the mapping. ) 

After that, we can start installation for the mapper, open up the pole-tip doors etc.

Yours relatively very relaxedly,

Kin

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