sPHENIX discussion of the superconducting solenoid

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

Hi,

(1)   Roberto told me that he’s needed to stop the plant as it has had some problem.  He’ll restart it and the fast(er) cool-down will happen tomorrow morning.  ( Probably we don’t build inventory before 4.x K. )   The outlet temperature now is down to ~215 K.  I’m very much looking forward to the fast cool-down.

 

(2) Mea Culpa :  Apparently, for the strain DAQ system, last night at 6:01 pm, I moved files instead of copying, Labview couldn’t find files to write to.   I’ve just realized the problem when I went to check it again a few minutes ago.  I restarted the strain system and it’s taken data again now.  So, the strain gauge system didn’t take data in the last 23 hours L   But the other DAQ system (with linear pot.) have been taking data without missing anything J

 

(3) This morning, Sonny, Ray and I went to 912 to take a look at the linear pot. 4.
For each pot, one can see a "pin" gradually going into the Magnet (when the contraction happens).  This morning, for pots. 1-3, each pin still has a little bit exposed outside but for the pot. 4, it's completely "suck in".   Ray’s opinion is that there was a sudden movement >0.125 inches (maybe due to bellow ?) and the pot. 4 reached its end.  It was reading what it supposed to read (0).   Pot. 3 and 4 are connected in series actually and so the 1 A was/is flowing through so that pot. 4 can't be really physically broken.

So, pot. 4 is gone (reached its end).    All the other pots will also reach 0 before the cool-down is complete.   We should have set them at >~0.3 inches at the beginning, rather than in the middle ~0.21 inches.   Too late now. 

Last time I checked (half an hour ago), the working 3 pots had only 0.0513, 0.0703 and 0.0835 inches left.    The largest contraction (pot. 1) has been > 0.15 inches so far.

(4) Today, I’ve learnt to calculate/estimate the contraction (from room temperature to 0 or 4 K) ~0.4%, from Roberto and Jim (+ google).  I’ve gathered my knowledge and written a few lines here:

https://collab.external.bnl.gov/sites/sPHENIX-Magnet/SitePages/Glossary%20+%20Knowledge.aspx#LowTemp

which includes the Duthil’s paper sent to me by Jim and the formula that I found from cryogenics.nist.gov.  Basically when T -> 0, the leading term ~-0.413% is dominates the Al.

Kin

 

 

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