Sam and I have been investigating a ~40 Hz peak in the HAM ISIs and PEM accelerometers, first noticed by Camilla and Sheila in alogs 79001 and 78879. Jim also investigated and suggested the peak may be caused by gain peaking from the isolation loops (alog 79145). The peak is strongest in HAMs 2, 6, and the LVEAFLOOR YCRYO Z accelerometer. We tracked the first appearance of the peak to May 20th. We've found there are actually two peaks roughly 0.2 Hz apart, which drift a bit in frequency from ~39.45 Hz (20/05/24 16:00 UTC) to ~40.2 Hz (20/05/24 22:00 UTC), measured from the point between the two peaks (see 1st attachment). The peaks consistently remain about 0.2 Hz apart in frequency but they do not always have the same magnitude ratio, even between channels measured at the same time (see 2nd attachment). Overall, the peaks vary in magnitude, occasionally disappearing altogether, but we have yet to find a time when one peak disappears and the other doesn't (see 3rd & 4th attachments for peaks disappearing and reappearing, respectively). We'll continue looking into surrounding peaks and the coherence with DARM.

16:09 Tue 23 July 2024 PDT the atomic clock jumped to +0.42S out from the Timing system.

This is the third time this has happened in the past month. Prior to that it had only happened once in the past year, on 4th May. Here is a table of the atomic clock out-of-syncs for the past year

I have extended the timing comparator's tolerance to 0.9999999 seconds to 'green up' the corner station timing.

Wed Jul 24 08:05:48 2024 INFO: Fill completed in 5min 44secs

Jordan confirmed a good fill curbside.

TITLE: 07/24 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 4mph Gusts, 2mph 5min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.05 μm/s
QUICK SUMMARY:

Close to getting the AUX laser aligned (79291)!

TITLE: 07/23 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Corrective Maintenance
INCOMING OPERATOR: None
SHIFT SUMMARY: Work today was just a continuation of work on aligning the AUX laser
LOG:                                                                                                                                                                                                                                                                                                          

Site wide power glitch at 13:43:30 PDT (20:43:30 UTC) Tue 23rd July 2024. Lights in corner station flickered. Both end station HEPI Pump Controller VFDs tripped.

Jim untripped the EX VFD, but the HEPI pump controller does not seem to have control. Jim and Patrick are investigating.

The ISI watchdogs for both ST1 and ST2 on the ETMs tripped seemingly randomly this afternoon at 20:43UTC. From the CPS sensors on ST2 and the T240s on ST1.

Dew point measurement done this morning, read at -43.4 ^oC.  There was some demand already on the system from HAM5, since both soft covers were off.  No demand from HAM6 or HAM7.  Flow was opened later to HAM6, since more personnel started working in-chamber.  HAM7 remains valved out.

I took the OPLEV charge measurement for the both the ETMs this morning as they were free. As I started I noted that ETMX had an FPU error (floating point unit), and during the measurement ETMY had lots of overflows, all stemming from H1:FEC-98_DAC_OUTPUT_3_3 (ETMX did not have any overflows).

To center the OPLEVs I had to do the following slider moves

ETMX sliders: P -42.7 to -57.8, Y -147.7 to -131.3

ETMX's charge appears to be increasing and high, its at or above 50V on all quads/DOF.

ETMY sliders: P 140.1 to 170.8, Y -162.8 to -149.0

ETMY's charge seems stable and low, hovering around 0-50 V on all the quads.

After I was finished I restored the sliders and re-misaligned the ETMs as they were when I found them.

We aligned the AUX laser in HAM5 so that it is roughly centered on OM1 AND is retroreflected by SRM. We haven't checked anything else.

Retroreflection was measured/evaluated using an iris right in front of the AUX laser launcher telescope. First the iris was well centered relative to the input light (1st attachment shows the scattering around the iris when it was closed down a bit), and we used a steering mirror and a beam splitter installed between the AUX laser and the SRM to get the SRM reflection coming back to the iris AND SRM transmission hitting the center of OM1 without touching SRM. It was easy. 2nd attachment shows the return beam on the iris after REALLY closing down the iris so the return beam clips on it. Centering on OM1 was based on just eyeballing using a sensor card.

We don't know where on the SRM or OFI the beam was (no easy reference). It seems that the beam was seen by ASC-AS_C but not centered on it.

The above was done before we were informed about a large ISI/HEPI rotation in YAW (alog 79272) so probably we'll do it again after moving SRM to compensate to get closer to the right alignment quickly (rather than walking the beam from where we are now slowly, checking the OM1 centering and SRM retroreflection many, many times).

In the end, we should make the SRM transmission hit the center of AS_C, make the beam retro reflected by SRM, and make the SRM reflection hit the center of SR2, all at the same time. For that, probably we'll have to make a minor adjustment to SRM.

Rick Savage, Dan Chen, Shingo Hido, Emmanuel Makelele and Dripta.

We went down to EY on Thursday, July 18th, 2024 to do a Pcal measurement, mostly to show the measurement procedure to our visitors. We used the procedure outlined in T1500062-V17 as a guide. A scanned copy of the filled out measurement procedures and log is attached.

Before we began the measurement, a picture of the beam spot position was taken. It shows that the beams were centered on the Rx sensor apreture (BeamSpotBefore photo attached).  

As noted in the scanned copy, after the first background measurement while WS was placed in the Tx module, the shutter stopped working. We could not open the shutter locally or remotely. The shutter has now been removed from the EY Tx module for troubleshooting. Pictures attached.

We continued with the measurement manually shuttering and unshuttering the laser. After taking all the measurements, a beam position picture was taken. It shows that the bemas remained centered and the Pcal beam spots did not drift significantly during the measurements (BeamSpotsAfter photo attached). 

Analysis and results/plots to follow. 

Genevieve and Sam asked about HAM1 and HAM2 motion around 40 hz. I hadn't look in detail in this frequency band for a while, this is typically higher frequency than we are worried about with ISI motion. But it turns out HAM2 is moving a lot more than HAM3 generally over 25-55hz, and particularly around 39hz. It looks like it might be due to gain peaking from the isolation loops, but could also be from something bad in the HEPI to ISI feedforward. The extra motion is so broad I don't think it's just one loop has a little too much gain, so I'm not sure what is going on here. 

First image are spectra comparing the motion of the HEPIs for those chambers (HAM2 HEPI is red and HAM3 is blue) and the ISIs (HAM2 ISI is green, HAM3 is brown). The HEPI motion is pretty similar, so I don't think it's a difference in input motion. HAM2 is moving something like 10x as much as HAM3 over 25-55hz. The sharp peak at 39 hz looks like gain peaking, but I'm not sure that explains all the difference.

Second plot shows the transfer functions from HEPI to ISI for each chamber. Red is HAM2, blue is HAM3. The 25-55hz tf for HAM3  is not very clean probably because HAM3 is well isolated. HAM2 tf is pretty clean, it makes me wonder if maybe something is messed up with feedforward on that chamber. Maybe that is something I could (carefully) fix while other troubleshooting for the detector is going on.