[Hallb-engineering] [Revised Logentry] Hall B possible contamination in 4K supply circuit

[kashy at jlab.org]

Logentry Text:
--
While writing a procedure to disconnect the Hall B Buffer Dewar (which is not needed for upcoming run or the following run) I noticed that the 4K supply pressure as read on PT8512 is reading 0.99 atm.
Plotting it I found that since July 2024 this pressure has dropped below 1.00 atm ~6 times with the lowest value being 0.66atm and this slowly rose for 13 days back to 1 atm (see plot attached). it is not clear if the pressure rose due to temperature rise, helium flow through a leaky valve or an air leak. 

Also of importance is that the data logger has not taken data since December 1 when the pressure read 0.9atm. Today it is reading 0.99 and even this alarmed me. I went ahead and set the LOLO alarm value to 1.02atm and made this a MAJOR Alarm. This needs to be put on the Hall B tech ON-CALL pager!

I have checked the pressures in the 4K supply circuits of the Torus and Solenoid over the same period none of the data available up to  12/1/24 shows their supply circuit going sub-atmospheric. This is good news.
At minimum, we must warm and purge 4K circuit of the DBX and the ESMTL to Hall B prior to magnet cooldown.  We also need to consider how to verify no water ice has built up on the isolation valves PV8512S and PV8512T.

Tomorrow I will start to work on a plan for this tomorrow and circulate it when it is ready to share.

Dave

---

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/4325262
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://mailman.jlab.org/pipermail/hallb-engineering/attachments/20250106/1673a18d/attachment.html>