J. Kissel, K. Venkateswara, K. Ryan

We finally figured out the issue behind the increasing current in the ion pump. In the morning, the current was near 1.5 mA, so we decided to do a leak check. There was a small leak through a flange but not enough to account for the ion pump behaviour. I fixed it by tightening the flange further and found no other leaks. Kyle then pointed out that we had the wrong polarity setting on the controller. The Starcell ion pump needed negative voltage not positive. With that sorted out, we restarted the pump. The current increased to ~10 mA, but has since been going down steadily. After ~1.5 hrs of pumping, it was at 0.49 mA at 7 PM. With the reversed polarity, we were probably just observing the leakage current, which may have been proportional to the pressure.

I've also attached an ASD plot of some data from last night, when the ground was fairly quiet. The red curve shows the BRS/tiltmeter output while the blue shows the T240 (incorrectly labelled as STS) converted to angle by multiplying by (2pif)^2/g. The coherence between the sensors is also shown.