Just had a couple of drops from Observing due to TCS_ITMY_CO2 guardian saying laser is unlocked and needed to find a new locking point.  (Attached are the two occurrences thus far).

Oli told me that the TCS CO2Y Chassis Tripped off during Maintenance this morning. This is not surprising as there was alot of craning work going on near that rack and the CO2 chassis are known to be fussy, see FRS 6639.

When I went to untrip it both indicator lights were red on it but after key-ing off/on, it turned on with no issues. 

Closes FAMIS 28463. Last checked in alog 85690.

CO2 Trends:

• IX Laser Power HD PD jumped down abruptly from 51.8W to 51.6W but is still above expected 35W. IY power is stable.
• Both IX and IY Laser Power MTR is above 1.7 for both IY and IX, (guide says that's the max) but it's only 1.73ish so I assume that's fine.
• IX chiller flow (purple) is not steady as the guide says is expected but jumps abruptly between 3.6 and 3.8 with 12 jumps back and forth in the last month. Additionally, the IX flowrate is also fluctuating and in one instance going below 2.8 GPM (which is the max). It seems to jump to 3 then slowly deteriorate over the course of a week and then jump back as the chiller changes it. Potentially worth investigation? Might be a known issue?

HWS FAMIS:

• Both HWS Sleds have been going down for the whole month. They started at ~2mW 42 days ago but IX went down to 1.3mW and IY to 1.7mW. Judging from last month's, I believe this is normal behavior?
• 22 days ago, both IX and IY probe spherical powers jumped. IX went from ~60 to 120 and IY from 30 to 60.
• While measured and simulated trends have a similar shape, the measured trends have that jump 22 days ago that I described above.

Plots attached

FAMIS 27821

No water was added to either chiller as levels are still good, although slowly dropping over the past several weeks. Updated T2200289 tracking sheet.

Filters and steel mesh in both chillers looked good. No water in leak checking cup.

TITLE: 08/05 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 152Mpc
OUTGOING OPERATOR: Ryan C
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 12mph Gusts, 6mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.09 μm/s
QUICK SUMMARY: H1 has been locked for 17 hours, but looks like there were three brief drops from observing between 11:33 and 11:40 UTC (I'm assuming SQZ-related, but will look into it). Magnetic injections are running and in-lock charge measurements will happen right after before maintenance begins at 15:00 UTC.

• Wind and ground motion low
• All other systems nominal

Jennie W, Camilla C

A while ago we heated up then cooled down the SR3 heater (alog #84749).

As part of measurements using this data I calculated the curvature change, following the approach at LLO by Aidan given iin alog #27262. Matlab code is below.

%calculate SR3 spherical lens

Pin = 2;%W

double_pass = 2;

SR3_t = (3*3600) + (11*60); % Time for cooldown in s.

delta_ITMY = -2.67e-5;% decrease in defocus of ITMY according to Hartmann sensor.

D_ITMY = delta_ITMY./double_pass;% defocus change in Dioptres

D_ITMY_error = 5e-6;% error on defocus in Dioptres.

R_SR3 = 36.013;% cold radius of curvature in m

delta_R = (2./((2/R_SR3)+D_ITMY))-R_SR3; % change in curvature during cooldown in m/

delta_delta_R = D_ITMY_error.*(2./((2./R_SR3)+D_ITMY)); % error on curvature change.

This means the rate of defocus change is 6.6750uD per Watt.

The final curvature change is + 0.0087 m +/- 0.0002 m as the mirror becomes less curved due to cooldown.

FAMIS27820

No water was added to either chiller, both at good levels. Updated T2200289 sheet.

Filters all looked good.

No water in leak detection Dixie cup.

TJ noticed the DCPD signals rising ~25 minutes into the lock, we found this was a PI t 10.215kHz. Matt notes that we've seen this at the start of each lock even before we changed the ring heaters last. It just damps down again by itself, we expect as the HOM pass over it. Plots attached. This PI doesn't appear to be in our monitored PI list.

TCS CO2Y tripped and dropped us out of Observing at 03:58 UTC then we lost lock 2 minutes later, lockloss. The lockloss appears to have been an ETMX glitch.

Closes FAMIS#28462 , last checked 84837

CO2 Trends (ndscope1)

Everything is looking good

HWS Trends (ndscope2)

Everything is generally looking good, with both ITMX and ITMY SLEDPOWERMON slowly going down, which they tend to do. The only possible concern I can see would be that zooming out to almost a year ago (ndscope3), it looks like the level that ITMX SLEDPOWERMON is at now is a lower value than it has been in the past year.

Closes FAMIS 27819. Last checked in alog 85440

CO2Y:

Before: 10.3ml

After: 10.3ml

Water Added: 0ml

CO2X:

Before: 30.4ml

After: 30.4ml

Water Added: 0ml

No water leaking in our leak detection system (aka dixie cup)

TITLE: 07/03 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Lock Acquisition
OUTGOING OPERATOR: Oli
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 5mph Gusts, 2mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.07 μm/s
QUICK SUMMARY:

H1 had (3)  ~2-hr locks overnight (looks like no wake-up calls for Oli!).  H1 is currently locking (just powered up to 25W).  Winds stepped down at about 130amPDT (837utc).

Today is Thurs Commissioning from 8am-12pmPDT (15-19utc).  H1 won't be thermalized until about 1030-11amPDT, so no calibration...hopefully H1 short locks won't be an issue for calibration where we need H1 thermalized 3hrs.  Robert and Sheila will probably start their work

M. Todd, S. Dwyer, C. Gray, A. Sanchez

We decided to set the ETMY ring heater back to 1W, as we were seeing PI24 having repeated dramatic ring ups. We expect this to set our LG10 y-arm mode to sit at 10490Hz once thermalized (fingers crossed). There are quite a few peaks around this region as well, but hopefully we move far enough away from PI24.

Saved the changes in SDF

Camilla, TJ, Dave:

Last Thursday 26th June 2025 alog85373 I restarted the HWS camera control code. We hoped this would improve the 2Hz noise comb in DARM. Initial results for F-Scan (observing) suggest it has not made much, if any difference. 

Attached F-Scans show the spectra on sun22jun2025 and mon30jun2025. The 2Hz comb (blue squares) look unchanged.

More investigation is needed to verfiy we are indeed disabling the frame aquisition on all HWS cameras when H1 is in observation.

Closes FAMIS#27818, last checked 85024 (I am a week late)

TCSX: 30.5, no water added

TCSY: 10.6, no water added

No leak in water cup

Lockloss during commissioning at 2025-06-25 17:52UTC after over 5.5 hours Locked. Cause not known, but probably not commissioning related.

Ansel, Sheila, Camilla

Last week, Ansel noticed that there is a 2Hz comb in DARM since the break, similar to that that we've seen from the HWS camera sync frequency and power supplies and fixed in 75876.  The cabling has not been changed since, the camera sync frequency has been changed.

Our current camera sync frequencies are: ITMX = 2Hz, ITMY = 10Hz. We have typically seen these combs in H1:PEM-CS_MAG_LVEA_OUTPUTOPTICS_Y_DQ. With a 0.0005Hz BW on DTT I can't easily see these combs, see attached.

M. Todd, S. Dwyer

As derived in previous alogs, we are able to relate the HOM spacing observed in each arm to the surface defocus of the test masses -- which is a combination of self-heating and ring heater power (ignoring CO2 affects on the ITM RoC). From the fits we've made of the HOM spacing / surface defocus change as a function of ring heater power we can get a value for the ring heater to surface defocus coupling factor.

Theoretically from this we should be able to solve for the self heating contribution in the test masses as well -- allowing us to constrain things like the coupling of absorbed power to surface defocus at the ITMs if we assume to know the arm power and absorption values (from HWS).

Upper Limits

If we assume no absorption in ETMs (obviously not physical), and we assume the HWS values for the ITM absorptions are correct, then with a HOM spacing measurement from each arm we can get an upper limit of the coupling factor of self-heating to surface defocus for each ITM (they shouldn't be different but this is a good exercise).

Assuming alpha is the absorption coefficient, i subscript is for the ITM, and x/y is which arm. P_y,i_rh is the itmy ring-heater. G-factors are the product of ITM and ETM g-factors. Then from the formula in section 1.2 of the notes file : Gy = Gyc - B*L*gyic*(Pyerh+Pyirh) - L*(Ai*alpha_yi*Pyarm*gyec + beta*Ai*alpha_e*Pyarm*gyic), we can solve for Ai which is the coupling factor of self-heating to surface defocus.

Middling Values

If we assume quoted absorption in ETMs (measured by LIGO, on galaxy), and we assume the HWS values for the ITM absorptions are correct, then with a HOM spacing measurement from each arm we can get a more realistic value of the coupling factor of self-heating to surface defocus for each ITM (they shouldn't be different but this is a good exercise).

Assuming alpha is the absorption coefficient, i subscript is for the ITM, and x/y is which arm. P_y,i_rh is the itmy ring-heater. G-factors are the product of ITM and ETM g-factors. Then from the formula in the notes file : Gy = Gyc - B*L*gyic*(Pyerh+Pyirh) - L*(Ai*alpha_yi*Pyarm*gyec + beta*Ai*alpha_e*Pyarm*gyic), we can solve for Ai which is the coupling factor of self-heating to surface defocus.

Summary

Both of these values indicate there is certainly an overestimation of the self-heating impact on surface defocus.

For reference, the current TCS-SIM values for this coupling factor are Ai_y = Ai_x = -36.5 uD/W.   More examination is required into this.

Links to previous alogs:

1. Estimating HOM spacing shift from self-heating alone:  https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=84172