It still glitches once in a while.

I'll install a coupler and a mixer to demodulate the PSL-45MHz signal by the 45MHz distribution amplifier output and monitor it using one of the ADC channels.

Done, nothing was fixed, need to watch out for the next episode (Vern, Keita).

In the attached left, at the beginning after Richard and Fil swapped the cable, RF45 was still glitching. After 19:03:50 mark there was a large glitch, that's when I decided to go in, and I wrote the above alog. The hope was to see if the glitch is likely to come from the upstream or not.

Of course, right after the glitch, it stopped glitching but I didn't know as I was preparing for the incursion.

I and Vern inserted a 20dB coupler to the PSL-45MHz line on the balun on the ISC rack, demodulated it using 45MHz distribution amplifier output from the ISC rack next to it, used a 1.6MHz(?) LPF, a 50 Ohm terminator, and finally SR560 to condition the signal.

SR560 setting was DC in, output zero at 1Hz and pole at 10kHz, with the gain of 2E4 with high dynamic reserve mode. (When DC coupled, the output was 2.3V with DC gain of 200).

The output of SR560 was connected to H1:LSC-EXTRA_AI_1 channel.

We waited for 40 minutes for a glitch but it did not happen (attached, middle and right).

Coupler was disconnected from the ISC rack, 45MHz distribution amplifier output was terminated, but the coupler/mixer/SR560 are left on the floor so it's easily put back on next time.

45MHz phase adjustment

Since RF cable was swapped (and the coil removed), I measured the RF phasing again. Using free swing MICH and measuring the TF from H1:LSC-ASAIR_A_RF45_I_ERR to Q, the phase was measured to be atan(3.45)=73.8deg.

I added a female-female and male-male N barrel in series and it was atan(4.50+-0.04)=77.5+-0.1 deg.

We are shooting for 76.4deg, and last time we adjusted it we ended up 77.3+-0.03, so I decided to go with 77.5+-0.1 deg.

IFO is currently down due earthquake. IMC/FSS stability is still erratic.

Plot of room temperature and RF45AM signal.  Does not appear to be a room temperature issue as there
are periods when the room temperature is just as high but there is no observed glitching in the RF45AM
signal.

Keita suggested tapping on the EOM box and wiggling the cable alog 23159. In the absence of anything better, that seems like a good idea.

The ifo is locked at NLN but not observing. RF45 still glitching.

Lockloss again at 07:00 UTC

DHARD ran away again. I lowered the gain as soon as I noticed the oscillation. The amplitude of the oscillation didn't seem to decrease. Maybe I didn't catch it quick enough?

I also couldn't connect to the nds sever. So no dataviewer.

I will be taking a few minutes to grief.....

Dataviewer seems to work on a different computer. Resume relocking.

Hmmm, maybe we just should always be using the lower DHARD gains when we're on the 45mHz ISI blends?  I think DHARD Pit is usually 10, and should go to 7.  DHARD YAW is usually 15, and should go to 10.

I don't think that the oscillation that nutsinnee shows in the screen shot is the one that can be fixed by lowering the gains, that is around 0.6Hz, while the screenshots show an something happening at around 20mHz.  This large low frequency motion of DHARD yaw was happening durring earthquakes durring ER8.

I would be more inclinnded to leave DHARD gains alone or try to increase the low frequency gain for Yaw, depending on what was really happening (was this ground motion or a loop oscillation?).  I think that lowering the gain could actually make things worse in either case.

For a rough model of DHARD yaw loop with thee new boost added, see https://alog.ligo-wa.caltech.edu/aLOG/uploads/21768_20150921225603_DHARDYAWOLGwithboost.png

RF45 mod gain decreased to 20.2 dB.

If you go more than 2 dB lower than nominal you risk unlocking the interferometer. There is also no clear evidence that reducing the modulation depth fixes this issue, but of course it doesn't hurt to get another data point.

I can see that DHARD isn't happy. I put the gain back to 21.2dB.

I just noticed SUSETMY has timing error. I hit Diag Reset to clear this. ETMY saturation continues.

Observing again at 01:20 UTC. ETMY continues to saturate. I don't think there's anything else I can do to help.... If you have an idea please call the control room.

Decreased RF45 MOD to 20.2 dB again after RF45 amplitude increased and stuck there causing DARM noise floor to rise. Forgot to go out of Observing when changing the gain.

I called Mike and he suggested I take the ifo out of Observing and wait until the RF45 situation gets better. The BSN range is at 15-20 Mpc at the moment. RF45 MOD set to 21.2 dB.