[Hallb-engineering] [New Logentry] Buffer Dewar Controls

[kashy at jlab.org]

Logentry Text:
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Some fraction of the issues we have been seeing on the magnets ramping down is coming from the buffer dewar and the Saclay Target.
The target is running in the batch fill mode. This mode creates the least ice on its return lines from the target and is also the most economical cryogenic power wise.
But it also causes unstable flow in the return U-tube from the buffer dewar this sends warm gas pulses back to the distribution box and these warm pulses warm up the supply to both magnets.
I have done some more retuning of the buffer dewar controls and these have reduced this effect, but not completely eliminated it. I may try to overfill the dewar but would want to try that on the next beam studies (hall B open). Attached is a plot of the past ~24 hrs. one can see the blue line with major spikes. The scale of this plot is -60 to 40 and the Dewar return TD8522DR is spiking to mid to upper 30's K. since just before noon today the new tune has reduced the duration of the spikes and thus their effect on the Torus and solenoid.

NOTE on the plot. The data logger is not set up to record minor changes in the supply temperatures so the plot looks a bit better than the actual improvments thus far.

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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/3527568
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