sPHENIX discussion of the superconducting solenoid

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

Hello,

 

1. Today, I’ve accompanied Carl Schultheiss the whole day in 1008B to compile and fix an old program to measure the joint resistances.
   This morning, we first gladly confirmed that the reason we read 1E38 on Wed. afternoon/evening was because the old C program had

set a limit of 1V whereas we were trying to read 3 V (from a battery).  I found from google about this “overflow” signature of

“1E38” Wed. night .

 

But then we found that we could measure some non-zero values only for the 1^st joint but always zero for the other two joints.  ( We have only 3 working 3458A meters. )

It took Carl (or us) several hours to realize that it’s due to a “double” and “single” precision formatting problem in the code as the other two joints had very small

voltage values like E-5 .

( Today, Carl also disabled the -ve Mag. Lead --- related to the known bad voltage VT10 since ~2018 --- in the Labview program by giving it a 10 V threshold. )

And then we successfully made measurements from 0 to 500 A in the steps of 50 A, and later from 500 A to 4620.3 A (all being set points) in the step of 500 A.
( Carl will try to analyze and show us the results soon. )   This was a good effort/outcome for today, if not for the following accident.

2. The Magnet was “happily” at the top current 4620.3 A (set point … DCCT = 4596 A) after 8 pm. 
   
   For the sake of electrical safety, Carl wanted to close the backdoor of the quench-detection rack.  In order to do that, he needed to detach the test lead wires from
   the connectors in the back of the quench-detector rack.  Though I worried about it, Carl thought that cutting the test lead wires was the cleanest way of doing it
   and shouldn’t cause trouble.  Unfortunately, while Carl was cutting the test lead wires, we heard the loud “boom” sound from the contactors of the Dump Resistor,
   i.e., a fast-discharge at 8:16, just ~6 minutes after the Magnet was at the full current ☹
   
   
   
3. Around midnight before Friday, I started to bring the Magnet back to the full current, after the Cryo cleared the permissive and interlock signals for us and
   I had CAS-Watch (Ron Walker) close the “Dump Resistor Contactors” in 1008B (manually--- the only way). 
   
   It’s just gone to the full-current.  I hope it will stay there for a while ….

 

 

 

Kin