J. Kissel

I've processed yesterday's measurements, found that the ETMX data was junk anyway, so I retook both test mass charge measurements. Attached are the result. The trend of charge accumulation continues, without fail. I wish I had thought of this sooner, but for the duration of the vent, I've turned the BIAS on both end station's ESDs OFF. This way they at least won't accumulate any more charge for a ~week. It won't make a big difference but it's something. 

Immediately after we've recorvered the IFO and we're satisfied with its operation, we *need* to flip the BIAS sign to begin to mitigate what charge has accumulated.

Also -- it would be really nice if we identified the source of the residual free ions in the chambers and reduced the accumulation that way. A while back, I'd started to work with the VE team to identify the remaining potential sources (see LHO aLOG 23906), but it feel off my radar to continue to push when I found so little documentation of the gauge array. Also, though we'd ruled out photoelectric emmission from the ALS system early on, it might be worth a reconfirmation, but I'm not sure we can go as long as we'd need to see an effect without the ALS system. Anyways, here's hoping someone out there gets re-excited about this.