kyle.ryan@LIGO.ORG - posted 16:49, Wednesday 06 September 2017 - last comment - 18:25, Thursday 07 September 2017(38537)
Y-end configuration restored, GV18 opened
Kyle, Gerardo Today we leak tested the new 2.75 CFF, valved-in the RGA and NEG pump, dumped GV18's unpumped gate annulus volume into the adjacent (pumped) annulus volume and opened GV18. This completes WP #7139 and #7139. Attached is the pumpdown. Note: the controller for the Y2-8 ion pump is showing 5600V, 1.0 x 10-11 Torr and 0.0 microamps pump current - hmmm. I STOPPED then STARTED the HV but get same reading. Neither the "Torr" nor the "current" are as expected. This might be related to the controller setup parameters. Otherwise, the pump isn't actually pumping! I'll consult Gerardo tomorrow.
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Comments related to this report
Another ion pump cable issue?
What does X2-8 read?
Yes - the ion pump current could be at the limit of the controller's measurement circuit. Pressures on the two arms look to be the same now. I thought there was a factor of 10 difference yesterday but maybe I had the wrong glasses on. Kyle or Gerardo?
I checked the display of the controller for X2-8 this morning and found it displays the same as the Y2-8 controller. That's great and all and, obviously they are pumping, but I thought that we had observed leakage current in 300' HV cable that amounted to micro-amps. Also, as a general rule of thumb, you figure 1 micro-amp of pump current for a 100 l/s ion pump @ 1 x 10-9 torr. As such, we should be seeing 5 - 10 micro-amps of pump current in addition to any leakage current.
I suggest turning off one or both ion pumps and looking for a response on the vacuum gauge over a period of a day or more. Hopefully this would confirm that they are pumping. As to leakage current - maybe things have dried out significantly over the summer and therefore leakage has fallen? Need to get some of these signals into epics to enable trending.