sPHENIX discussion of the superconducting solenoid

[Kin Yip <kinyip AT bnl.gov>]

Hello,

This morning, Zeynep entered quite a bit of today's test details  into our Elog :
http://elog.pbn.bnl.gov:8080/elogs/entryList.jsp?ELOG=sPHENIX-Magnet-High-Field-Test_2018

So, with Gpm & LogView and the above Elog, you can pretty much see what Carl/Pablo/Zeynep were doing in 912.   [ This is what many
accelerator physicists did during the RHIC Run. ]

This morning, we ramped successfully at 1A/s to ~1000 A (highest ~2746 Gauss) and stayed there for almost 14 minutes.   Then,
Carl/Pablo/Zeynep decided to perform an intentional fast discharge ( tripping the quench detector by lowering the threshold
for the positive gas cooled lead to 5mV from 50mV).

Later, after the Cryo recovered, they tried ramping at 2 A/s to 500 A but when they reached ~493 A, an unintentional fast
discharge was triggered.  From the LogView, one can see that "Intlk_Quench_Event" dropped first before everything ?!    So, Carl and
others are investigating what caused the "Intlk_Quench_Event" to drop.   Since the Cryo tank was ~10%, they decided to stop
for the day.   The consumption was again 8% per hour, like Monday, and faster than previous weeks (6.5% per hour)  :-(

I attach the usual Current and Magnetic Field plots.

A couple notes:

1.  In the plot, I also showed the (invalid) power supply current.  On Monday, we noticed an unreasonable difference of almost 300 A between PS_current and Magnet_current.
This morning, Carl/Pablo/Zeynep have figured out that it's something wrong (settings ...) in the DCCT of the power supply.   [  The Magnet Current has another DCCT for measuring current. ]
And these two signals used to be the same (though different names, say, a month ago; but recently, Pablo gave the real power supply signal to Carl's data-acquisition system. ]
So, Pablo will work on it.  It was unplugged later and it stayed at ~400 A :-)

2.  On Monday (Jan. 29), strain gauge stopped to work ~2:30 pm when we were ramping up the current.   Today, it worked throughout.  But there were no large/obvious/interesting rise for the strain gauge
signals, not the linear pots etc.   Only a tiny bit (if any).

3.  Hopefully, we learn something useful from the analysis of today's event at the end and prevent it from happening again.  This test is essentially a training for the quench detection.


We'll run again next Monday Feb. 5 at 9 am.   Paul Orfin and Carl/Pablo/Zeynep have all agreed with this time  when I asked them individually. 

Kin

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