[Hallb-engineering] [New Logentry] Hall B solenoid cryogenic stability

kashy at jlab.org kashy at jlab.org
Mon Jun 14 18:35:01 EDT 2021

Logentry Text:
There is an ongoing intermittent stability issue in the Hall B Solenoid system. During the SAD we found a CVI Pumpout on the long return U-tube which had a dirty o-ring that leaked, and we replaced it. This likely fixed a cryopumping load (heat load). Now with lower heat load the 4K supply valve can close more and stay on its minimum value longer and due to the long time before the return warms up (control is on the return temperature from the solenoid in the DBX) the Solenoid U-tube warms up first. Then with warm gas mixing with cold gas in the U-tube the the supply pressure increases sometimes blowing a relief valve and sometimes dropping the helium level.

 I've re-tuned the PID loops for this valve see the attached picture. It is looking better so lets see how it goes over night and longer if it is looking good.


This is a plain text email for clients that cannot display HTML.  The full logentry can be found online at https://logbooks.jlab.org/entry/3880348
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