[ericq, Gautam]

The length of DRFPMI lock did not increase much tonight, but we got a ~80 second sensing matrix measurement, and got the CARM bandwidth up to 10k with two boosts on. 

NB: I did not measure the CARM loop gain at its excitation frequency, so the plotted sensing element is supressed by the CARM loop. However, this is still useful for gauging the size of the PRCL signal vs. the residual CARM fluctuations. The excitations are fairly closely spaced between 309 and 316 Hz. 

For comparison, I'm also re-plotting the DRMI sensing measurement from a few weeks back taken at CARM offset of -4. We can see some change in the PRCL sensing, likely due to the CARM-coupled path. MICH/PRCL sadly looks pretty degenerate, but REFL55 looks more reasonable. 

I think the main limitation tonight was SRC stability. Even before bringing CARM to zero offset, we would see occasional sharp dives in AS110 power. One lockloss happened soon after such an occurance, but I checked the values, and it was not sufficient to trigger the Schmitt trigger down; instead it may have been a real optical loss of signal. The SRCL OLTF looks sensible. 

Random notes:

• Aux X laser was glitching yet again, twiddled laser current to 1.90A from the 1.95A that I twiddled it to on Monday from the nominal 2.0A. 
• When aligning the PRMI, I saw both ITMs' oplevs shift by a few urad in both pitch and yaw when engaing/breaking the lock, but this was not repeatable.
• I reduced the AS110 whitening gain by 9dB, since the DC values were a few thousands, and I wanted to make sure there were no stray ADC saturations. This didn't change lock stability though.