J. Kissel, K. Venkateswara

This morning I modified the laptop code to write two additional channels into aLIGO DAQ: One writes the tilt channel but with a lower gain such that it covers the entire range of the CCD. Obviously this doesn't reach the full sensitivity of the autocollimator but is useful as a diagnostic check on the DC position of the balance. The high-passed tilt channel doesn't give that information. The second channel, I added, writes the reference mirror position.

I also noticed today that the Ion pump current was at 0.48 mA this morning, whereas it was about 0.38 mA on Saturday evening. It continued to rise to about 0.58 mA by today evening but appears to be leveling off. It may be an effect of 'saturation' of the pump. We will know by tomorrow, when we look at the trend.

I also did a quick look at the data from the weekend and I've attached a couple of graphs. The first is from ~10k seconds on late Saturday night-early Sunday morning, when the ground was very quiet. There appears to be some excess noise in the BRS channel between 10 to 60 mHz, which is not tilt. Additionally, there are lines present at the harmonics of the beam resonance, due to small non-linearities in the read out. On Sunday night around 8:30 PM, there was an earthquake which shows up clearly in the T240 data, but is not visible in the BRS data. The second plot shows the ASD of 10k seconds during that period. This is preliminary and I'll do some better analysis soon.