Most of tonight's work was measuring the HARD Pit loops, to give them some low noise settings to match the pre-existing Yaw low noise settings.  I also tried moving around the spot position on the AS_C QPD, which is pretty much the only QPD whos offsets we haven't tried tweaking lately.

It's clear on the AS camera as well as on the ALS X green camera that something moves significantly between 2W and 50W in yaw.  I was hoping that perhaps adjusing the SRC alignment would help with this somehow, but it didn't.  What I do think it might help with though is the fact that previously, we've seen our sideband powers drop significantly when moving POP and Soft offsets to increase the carrier power recycling gain.  I haven't tested this yet though. The first two attachments show the improvement in AS90 and the AS90/POP90 ratio when the AS_C spot is moved.  The max value in yaw that I moved was to 0.94, but this was obviously too far.  Perhaps tomorrow I'll picomotor a little bit so I can go a little farther, if this indeed helps the sideband buildups.

I moved the filters in the CHARD loops around today so that I could fit in a new lowpass at 200Hz.  CHARD has been acting funny lately, and is likely why we've been tripping the quads' rms watchdogs the last day or so.  To at least help, I put in a high-freq cutoff so that we can at least limit the amount of sensor noise we send to the quads.  Probably we should add this to the DHARD loops too, since none of them have had cutoffs of any kind during the acquisition sequence for a long time now.  I modified the ISC_LOCK guardian, as well as the sensing matrix code to be aware of the new locations of the different filters.

I measured the HARD pitch loops several times while modifying the loop shapes.  Both Chard and Dhard now have 50W modifying filters that move the plant compensation frequency response to match the 50W resonant frequencies rather than the 2W freqs.  They also both have a 25Hz cutoff.  CHARD Pit I can lower the gain by a factor of 2, but DHARD pit I can't. Most of the measurements in the attached screenshots are with the BoostHBW still on.  These should have been turned off, and are turned off for the Yaw loops when we go to low noise mode, in order to win back enough phase to reasonably have our cutoffs.  I need to think more carefully about how much gain we need at what frequencies before I finalize these loop shapes, but it seems like (from the DHARD pit measurement with the boost removed) that I should have enough phase to move the cutoff lower, if I don't require all that gain at low frequency. 

The guardian is up to date with these changes - other than helping the still-cooling IFO with some alignment while trying to catch DRMI lock, you can just request Lownoise_ASC, and the IFO will go up to 50W and hang out.  (I've commented out all of the offsets in the Adjust_offset state, but other than that, things are all as they were, modulo the changes mentioned above.)

Terra is writing up our PI experiences and mysteries from today, but I expect that the IFO will stay locked for just under 3 hours, so I'm going to put it in Observe just in case the data groups want to test pipelines.  The noise is still bad though, especially the intensity noise coupling as the IFO thermalizes.  To do this, I changed the nominal IMC_LOCK state to ISS_TR_CLOSED rather than the usual ISS_ON (which implies 2nd loop on), since we can't close the 2nd loop right now - we need the new hardware so that we can have both 2nd and 3rd simultaneously.

Oooh, I almost forgot.  Sheila and I tried closing a dither loop around the PRM to keep the spot position on PR2 constant.  This seems like it was doing good things, however once she fixed the 3rd loop's SR560 we decided that it would be good to get back to a campaign of persuing low noise for a while, rather than chasing offsets around.  We should consider coming back to this though when we come back to offset moving for PRCgain improvement.