Tonight we paused after a lockloss to look at the refl beam. With PR2+PR3 misalinged and PRM, I turned on the refl WFS centering servos.
First I tried to move both PRM and offsets inthe centering servos to see if there was an alingment where there is more light on the LSC refl diode. There seems to be the maximum power on the diode when we have no offsets in the centering loops and PRM has the same alingment as durring a high power lock according to the osems. There is no evidence for clipping here.
Then I had a look at the RFAM, both by looking at the digital readback of REFL 9I and using a spectrum analyzer ( I lost the data from the analyzer in a floppy disk mishap). BY unplugging the 9MHz modulation to the PSL, I got a reference for the noise that is not due to RFAM (shot noise, ADC noise, 60 Hz harmonics). Just looking at the level of noise in the attached screenshot, and Evan's coupling measurement (29893), you would estimate that this noise is at the level of a few time 10^-21 m/rt Hz in DARM.
I also got some data for OMC length noise measurements, but will post those tomorow.
I am leaving the IFO undisturbed, in basically the nominal state. The beam diverters are open, and the OMC dither frequency is shifted to 4050.
There are many guardian nodes that aren't in their requested state (mostly sus guardians) which is probably because of a restart today, but prevents us from setting the intent bit to undisturbed. They are mostly in init.