Attached is a plot of IM4 Trans qpd and ISS 2nd Loop qpd signals.

First plot - top - shows that IM4 Trans Pitch and ISS 2nd Loop Pitch don't match well

First Plot - bottom - shows that IM4 Trans Pitch is a good match to the ISS 2nd Loop Yaw signal (yaw modified: multiplied by -0.7 and an added offset of 0.005)

Second Plot - top - shows the IM2 Trans Yaw and ISS 2nd Loop Pitch - raw data

Second Loop - bottom - shows the IM2 Trans Yaw and ISS 2nd Loop Pitch (pitch modified: multiplied by -0.3 and an added offset of 0.8)

The DCS Disk2Disk scripts at LHO, which copy data from CDS to the LDAS archive and scratch disks have been restarted to use the CDS h1fw1 framewriter as the primary source of frames. The backup is h1fw0. This will prevent LDAS from picking up "bad" h1fw0 frames, except in the very unlikely event h1fw1 is down and h1fw0 writes a bad frame at the same time. (See: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=29521 for the latest on the h1fw0 issue.)

Began 15:22 UTC, finished 15:24 UTC

As soon as the restart finished IPC was red. I hit diag reset button and it went away. OAF_L0_MADC1_EPICS_CH25 started to overflow pretty much as soon as the model restart was done.

TCS chillers and lasers are recovered.

The laser tripped this morning.  From the laser MEDM screen it looked like the NPRO had tripped which would pull
the entire system down.  However the Beckhoff screen indicates otherwise; that the fault is associated with the
crystal chiller.  It should be noted that the crystal chiller has 10468 hours on it.

    Logs indicate that it tripped around 3 am.  Unfortunately I did catch the trip.

    Further inspection shows that the laser tripped not because of the crystal chiller (see AMPFlow.png).

    Might be due to flushing of the newly deployed (old) manifold.

Sheila, Terra, Jamie

Today I set up an OSA on ISCT6 to look at sideband assymentry at the AS port.  Mark stayed late to get an MHV cable together,  and we were able to look at the asymmetry in some of the 50 Watt locks that Jenne and Stefan had.  Roughly, we saw that the asymmetry of the 45 MHz sidebands is 66% in power, while the 9 MHz sidebands are about a factor of 3 different in power.  We have left the set up in place for now, and we will make some plots tomorrow.

Jenne, Sheila, Matt, Stefan, Terra, Jamie, Robert, Kiwamu commissioning

Still needing to stop at LOCK_DRMI_1F to minimize ASC error signals before engaging control loops. The TCS chillers tripped from a DAC error and were reset.

23:18 UTC Sheila to ISCT6
00:19 UTC Sheila back
00:37 UTC Sheila to ISCT6
02:00 UTC Sheila back
03:23 UTC Restarted frozen video2

Sheila, Jenne, Terra, Patrick

It appears that we have the same situation as described in alog 27435.

Following the suggestion of alog 29522 we switched the ASC input matrix for MICH_P and MICH_Y (the BS).

The final matrix was

MICH_P = 1.5*AS_A_36_Q_PIT    + 0*AS_B_36_Q_PIT
MICH_Y = 1.5*AS_A_36_Q_YAW + 0*AS_B_36_Q_YAW

the old matrix was

MICH_P = 0.666*AS_A_36_Q_PIT    + 1*AS_B_36_Q_PIT
MICH_Y = 0.666*AS_A_36_Q_YAW + 1*AS_B_36_Q_YAW

We did the ransition slowly over about 30min. Interestingly the SRM dither loop did a nice job, and the different offset in the error signal was not an issue.

We stayed at 50W a total of 40min.

Keita Marc Fil Daniel

We realized that we can implement the required compensation for the second loop by using the whitened monitor signals (TP10) from the transimpedance board as the inputs to the sum of PD1-4 and PD5-8, respectively—instead of the unwhitened outputs from the transimpedance amplifiers.

The required modifications are:

1. Add a 220K resistor in parallel to C29 and C30 (4x channels on 2x boards)
   This limits the AC coupling and gives a DC gain around 1.
2. Replace C25 and C26 (4x channels on 2x boards) with 47 pF.
   This gives the signals a wider bandwidth.
3. Lift the input side of R48/R49/R51/R52 and jumper it to TP10 (4x channels on 2x boards)
   This rewires the inputs of the sum amplifiers.
4. Change R38 and R39 to 4.87K (from 4.53K).
   This brings the poles better in agreement with the ones form the second board.

I stopped and reran the Hartman code for ITMX at around 21:30 local.

We had an interferometer that was nicely thermalized at 20W today, including a 900Hz frequency line to monitor the REFL9I and REFL45I gain. So we decided to investigate the influence of common TCS on both AS_90 and REFL45 gain.

We thus increased the TCS CO2 central heating by 1W on each optic (to 1.2W on X, 1W on Y). This resulted in a DECREASE (at least initially) of the REFL45 gain (the opposite of what we see going to high power), and at the same time a recovery of the AS_90 buildup.

After letting it settle for about 50min in this configuration, we went to 50W. To our surprise the sign of REFL45I changed. We can only explain that by the 45 sideband going through critical coupling. This would mean a number of our loops in REFL changes sign, so it is not surprising that we lost lock soon afterwards.

The attached plot illustrates that story. Blue: REFL45I gain, Green: REFL9 gain, Orange: AS_90

PSL/IOO jitter coupling is high, so, as a first step, we adjusted offsets on IMC_DOF_1(2)_P(Y). We adjusted offsets to minimize peaks in DARM from a 290Hz pitch (1500 counts), and a 310 Hz yaw (390 counts) injection, made using the piezo mirror on the PSL table. The second loop of the ISS was off, and we were at 20 W. This was a first rough alignment (the offsets were at 0). Only DOF_2_P and DOF_1_Y seemed to have much effect. The figure shows that we improved jitter coupling by a factor of 3 or 4 in both pitch and yaw, with the best improvement in pitch. Next we will adjust the ISS array picomotors.

The proposed settings change follows:

IMC_DOF_1_P, was: 0, proposed: 0

IMC_DOF_2_P, was: 0, proposed: -100

IMC_DOF_1_Y, was: 0, proposed: 50

IMC_DOF_2_Y, was: 0, proposed: 0

Robert, Kiwamu

Last night, we ran a quick TCS test where we attempted to minimize the intensity noise coupling to the DCPDs by changing the CO2 differential heating.

It seems that the following CO2 setting gives a much better intensity noise coupling when the PSL power is 25 W:

• CO2X = 460 mW
• CO2Y = 0 W

This did not improve the recycling gain so much. It seems to have increased by 2% only.

According to a past measurement with a lower power PSL of 2 W (alog 26264), a good differential CO2 power had been found to be P_{co2x} - P_{co2y} = 270 mW (or probably less than 270 mW because I did not explore the lower differential power).

This could be an indication that ITMY has a larger absorption for the 1064 nm light such that the differential self-heating linearly changes as a function of the PSL power. We should confirm this hypothesis using the HWS signals.

[The test]

No second or third loops engaged, DC readout, no SRC1 ASC loop.

• 3:34 UTC, full resonance with 2 W PSL
• 4:12 UTC, PSL --> 25 W
• 4:24 UTC,  CO2Y 260 mW --> 0 mW
• 4:49 UTC, PSL --> 22 W for letting the 0.5 Hz instability go away
• 4:56 UTC, CO2X 480 mW --> 790 mW
• 5:12 UTC, lock loss

Drastic reduction of the intensity noise coupling was observed mostly between 4:24 and approximately 5:00, indicating that reducing the CO2Y power helped improved the coupling. After 5:00 UTC, we did not see a significant reduction. This may mean that we might have been already close to an optimum point where the coupling is minimized. The attached shows DARM spectra from various time during the test.

A broad peak at around 400 Hz is my intentional excitation to the first loop with band-passed gaussian noise in order to check the coupling to the DCPDs. As shown in the spectra, the reduction from the beginning to the end of the test is about a factor of 5. As reported in 27370, broad noise above 100 Hz up to several kHz is indeed intensity noise and therefore we see the noise floor in this frequency band decreasing too.