Current set points of local controls for the PR2 pitch and yaw are different from previous values.
This is probably one of the reasons why the current jitter and frequency noise couplings are larger than before.

It might be better to get back previous set points if we cannot find good WFS offsets with the current PR2 alignment.

Abstract:

Since there is large peak around 140Hz, I reverted alignment to the one during last week to investigate the reason of the peak around 140Hz.
However, even though all settings were reverted, there was a peak around 140Hz.
Since the peak height sometimes became small when tweaking WFS offsets, it would be reduced by alignment, so I continued alignment tweaking today.

Detail:

According to the spectrum during the night run yesterday, there is a peak around 140Hz while it was not there last week (fig1: blue cursor).
Alignment setting during last night was different from the one last week, especially ITMY beam spot is closer to the center, so I checked if the peak appeared due to ITMY beam spot or not.
Since the peak looks broad and the sensitivity around 140Hz affects BNS range, further sensitivity improvement is expected if we remove that peak.
So, I reverted IFO alignment setting to the one last week and checked the sensitivity.

Since GRX seems to move a lot, especially in yaw, I first checked the beam spot on PR2 by using both POP FORWAD QPDs and PR2 BPC signals to confirm IR alignment doesn't change.
Figure 2 shows the QPD signals after reverting IFO setting, which seems to be fine (Y cursor shows the values last week).
In addition, BPC signals cross to zero (apply 5 cnts from CLK GAIN), which means beam spot on PR2 should be almost centered.
So, there seems no change in IR beam path.
After confirming that, I aligned GRX by using PICO motors on POP table.

Then, I checked the sensitivity with the reverted alignment and found that there is a peak even with this configuration (fig3).
Therefore, it doesn't seem to appear due to ITMY beam spot yesterday.
So, I continued the alignment tweaking with ITMY P2L drive align matrix of -1.6, which is smaller the the original value (-2.5), to reduce the pitch thermal noise.

Changes during the work:

During the BPC signal checking, I modified the filter of K1:BPC-YAW_PR2_DEMOD_{I,Q} filters (fig4, fig5: added LP0.1).
In addition, I increased gain of ETMX tidal compensation (FM1, FM2, and FM3 of IP_ISC2LVDT_L filter bank) to supress the MN actuator feedback signals and reduce the breathing around 80 Hz.
I also changed all WFS offsets to zeros because offsets sometimes disturbs the ASC engagement during the lock acquisition.
After confirming the good offset values, it would be necessary to modify the guardian so that adding offset after ASC is fully engaged.

[Aso, Ushiba]

Abstract:

We tweaked ASC offsets and ITMY drive align matrix for ITMY BPC.
We found relatively good configuration, so we keep this configuration today.

Detail:

To obtain better ensitivity, we tweaked IFO alignment.
First, I reverted BPC setpoint and ASC offsets, PR2 PIT and IMMT1 PIT and YAW OpLev values to the one I set the day before yesterday and checked the reproducibility.
However, the sensitivity is worse, so we started tweaking of ASC alignment.

Since the beam jitter coupling around 200-400Hz is large, we started from MICH offset tweaking because beam jitter coupling through MICH is simple and we think it is the most effective.
Then, we tweaked PRC2/INP2 offset to reduce the peak around 116Hz.
Thanks to these alignment tweaking, 116Hz pek height is almost same as the best sensitivity while keeping the peak around 200-400Hz slightly better.
Also, GRX alignment by using POP PICO motors are conducted during the work.

After that, we changed drive align matrix of ITMY to change the beam position on ITMY to reduce 140Hz peak but no effect or even worse when moving beam spot.
So, we gave up tuning of ITMY BPC.

Final setting of ASC offset and BPC are as follows:
K1:VIS-ITMY_TM_DRIVEALIGN_P2L_GAIN = -1.4
K1:VIS-ITMY_TM_DRIVEALIGN_Y2L_GAIN = 0
K1:ASC-PRC2_P_OFFSET = -0.03
K1:ASC-MICH_P_OFFSET = -0.1
K1:ASC-MICH_Y_OFFSET = -0.04
The other WFS offsets = 0

After finalizing the IFO setting, I measured OLTF of DARM loop to confirm there is no significant change (fig1).
Since the OLTF gain change from the last CAL measurement (klog34310) is less than 0.1dB, current calibration should be fine.

Note:

YAW BPC of ITMY improves transmission power without changing optical gain.
Offsets on MICH ASC seems to affect 200-400Hz peaks, which originates from the beam jitters that can be seen in IMC WFS signal.
116Hz peak height can be reduced by changing PRC2 and MICH ASC offsets.

I tweaked beam spot on ITMY by changing drivealign matrix but no significant change can be observed even waiting for more than 1 hour.
So, I reverted ITMY drive align matrix.