Evidence linking PSL video cameras to the near-30 Hz (29.97 Hz) comb observed in DARM

[Joan-Rene Merou, Alicia Calafat, Sheila Dwyer, Robert Schofield, Anamaria Effler]

We have identified video cameras located in the PSL enclosure, operating at an NTSC-derived frame rate of approximately 29.97 frames per second, as the most probable source of the near-30 Hz comb (fundamental at 29.96951 Hz) observed in DARM.

This is a continuation of the work performed to mitigate the set of near-30 Hz and near-100 Hz combs as described is Detchar issue 340 and lho-mallorcan-fellowship/-/issues/3. As well as the work in alogs 88089, 87889 and 87414 and 88433.

Continuing with the magnetometer search described in alog 88433, we found out that the 29.96951 Hz line was very strong in the H1-PSL-R2 rack 12 V power supply. 

Tracing the cabling from this power supply revealed two distinct paths. The first one is a cable feeding a chassis in the H1-PSL-R1 rack, which connects to an Axis 241Q video server. This server supplies four beam cameras located inside the PSL enclosure. Then, a second cable feeding a small fused distribution unit, from which three white cables emerge. At least two of these enter the PSL enclosure directly, and the third appears to route upward toward the entrance area. These cables were identified as supplying three additional cameras in the PSL enclosure.

The relationship between the power supply, fused distribution unit, and cameras is illustrated in the diagram below.



On 2025-12-17, we went with Robert to disconnect the green power supply cable. Disconnecting the green power cable from the 12 V power supply caused the 29.96951 Hz line to disappear from magnetometer. Reconnecting the cable resulted in a gradual reappearance of the line. Disconnecting individual cameras connected to the Axis 241Q server produced no significant change in the comb amplitude, suggesting these cameras are not the dominant contributors.

In contrast, removing the three fuses from the fused distribution unit immediately eliminated the 29.96951 Hz line. Upon returning to the control room and restarting the cameras via the standard startup procedure (showed to us by Oli Patane), the line reappeared promptly.

This sequence strongly implicates the three cameras powered through the fused distribution unit as the primary source of the comb. The photographs below show the differences between having the 3 cameras on or off and the peak as seen in the voltage monitor plugged to the 12 V power supply.



According to /opt/rtcds/userapps/release/cds/h1/scripts/fom_startup/nuc21/launch.yaml, the three cameras identified above are Axis 215 PTZ Network Cameras. The Axis 215 PTZ have a maximum frame rate of up to 30 fps, NTSC-compatible video timing and Nominal NTSC frame rate of 29.97 frames per second.

NTSC (National Television System Committee) is an analog color encoding system used in television systems in Japan, the United States and other parts of the Americas. An NTSC picture is made up of 525 interlaced lines and is displayed at a rate of 29.97 frames per second. This frequency matches the observed comb fundamental (29.96951 Hz) to within <1 mHz, within expected drift for video timing systems.

Some sources:
 - Axis 215 PTZ Network Camera data sheet
 - Axis 215 PTZ Network Camera technical details
 - NTSC encoding system information

Another clue that pinpoints to an electronic origin is that the the line width is noted as 0.00042 Hz towards each side in the O4ab lines list (LIGO-T2500212). This means that the line amplitude is around 30 ppm, consistent with what we expect from an electronic element with its own clock (not tied to the GPS system) and this clock not being ultra precise.

It is possible that the way cameras are connected in LLO is different from LHO, or that the cameras themselves are different, which would explain why the comb is in LHO but not in LLO. Note that there is a line at LLO closer to 30 Hz but not at 29.97 Hz.

There are various changes that can mitigate the comb. Turning off the cameras would be the first one. Another idea is to turn of only 2 of the cameras, one in the entrance to the PSL enclosure and another one being one of the top corner in the PSL enclosure. Leaving one of the three there but reducing significantly the strength of the line. These cameras have an upper limit of 30 FPS. Getting more modern cameras at 60 FPS, thus moving the line to 60 Hz, could also be an idea.

Using the camera controls, we have also checked what happens if we change the frame rate of the cameras. When we reduced it to 1 frame per second instead of 30 frames per second, we were able to see peaks at every 1 Hz, while the peak at 29.97 Hz was much lower.


(Red line is a live voltage monitor on the power supply and blue one is a reference before changing camera settings)

On 2025-12-18, we have further investigated which one of the 3 Axis 215 cameras is responsible for most of the peak amplitude. These cameras are h1pslcam0, h1pslcam1, and h1pslcam2. In their default setting and default orientation, the peak amplitude in the voltage monitor PSD was around 150 1/Hz. We have then disconnected the three of them and reconnected them back on:
 - With only h1pslcam0 on, the peak amplitude was around 60-80 1/Hz.
 - With only h1pslcam1 on, the peak amplitude was around 40-50 1/Hz.
 - With only h1pslcam2 on, the peak amplitude was around 10 1/Hz.
 - With no cameras on, the peak cannot be seen.

Hence, it would appear that not all cameras have the same effect on the peak amplitude. h1pslcam2 is in the PSL enclosure pointing towards to table. From the other two, one also points towards the table and the other one is in the entrance room to the enclosure. Therefore, since h1pslcam2 has the smallest peak amplitude and has the same function as the other one in the enclosure, an option could be to just leave this camera on and turn off the other two ones.

Note that the near-100 Hz peaks do not dissapear from the voltage monitor if we turn off the cameras, which probably points to a different source.

We have further tested the settings in h1pslcam2 to see what else decreases the peak amplitude. We have seen that checking of the "de-interlacing" slighly also decreased the peak amplitude, from around 10 1/Hz to 7 or 8 1/Hz. Reducing the camera frame rate from 30 fps to 1 fps further reduces a bit the peak to 5 1/Hz. Reducing the gain in low-light in the camera advanced settings also appeared to reduce a bit the peak amplitude to around 4 1/Hz. Note that reducing the fps to 1 also creates small peaks every 1 Hz in the voltage monitors, but these are smaller than the one at 30 Hz:


(blue is a reference with the three cameras on)

On 2025-12-19 we produced the following table of plots showing the height of the peak at 29.96951 Hz, as well as the near-100 Hz peak at 99.998455 Hz and 2 of their intermodulations, one at 99.998455 Hz + 29.96951 Hz and another one at 99.99845486125*2 - 29.96951 Hz. Each row represents a different configuration:
 - The first row represents the actual default status with all cameras on in their default configuration.
 - The second row shows only having h1pslcam2 with its default configuration
 - The third row shows only having h1pslcam2 on with the configuration we have found optimal to reduce the 29.97 Hz peak (1 fps instead of 30 fps, no de-interlacing, low-light max gain of 0 dB and manual exposure control.)
Note that on 2025-12-19 while the reduction factor between the first and last configuration at 29.96951 Hz is still ~30, it began at a height of ~80 and went down to ~2.5 instead of from ~150 to ~5. As can be seen in the table of figures below, the 99.99 Hz peak does not change that much, while the intermodulations do become smaller as we reduce the height of the 29.96951 Hz line.



This appears a reasonable setting in which to leave the cameras if we want one on: h1pslcam0 and h1pslcam1 turned off. h1pslcam2 and the beam cameras turned on. h1pslcam2 checked off the "de-interlacing" setting, fps set to 1, resolution set to 4CIF (reducing resolution does not appear to have much influence), reduce the low-light gain below to optimally 0 dB and set exposure control to manual with the shutter speed to 1/60 s. This configuration is expected to reduce the peak amplitude in the voltage monitor from around 150 1/Hz to 5 1/Hz. This factor 30, if the same reduction takes place in DARM, should significantly reduced the peak and have a lesser effect on CW searches.

Note that in order to fully not affect CW searches, the optimal would be to just turn off the cameras. Looking at the O4ab averaged plots used to create the lines lists, the peak at 29.96951 Hz is over 2 orders of magnitude stronger than the surrounding noise. The peak is expected to be smaller in O4c given the change in H1:SUS-ITMY_L3_ESDAMON_DC_OUT16 bias studied in 87414, but only turning off the cameras would ensure getting rid of it.

In conclusion, the evidence strongly supports that the near-30 Hz comb observed in DARM originates from NTSC-timed video cameras in the PSL enclosure, specifically the Axis 215 PTZ cameras powered by the H1-PSL-R2 12 V supply. Powering them off and on, fuse removal, frame-rate manipulation, and frequency matching all independently confirm this attribution. Optimally, we recommend turning the cameras off or changing them. If one should stay on, we recommend having only h1pslcam2 on with the optimal configuration described above.

Fri CP1 Fill

Fri Dec 19 10:10:35 2025 INFO: Fill completed in 10min 31secs

 

IOT2 table disconnected and moved away from HAM2

This morning Fil disconnected the table, I removed the bellows and added viewport covers and lexan, and then Randy and I moved the table out of the cleanroom and to the side in the +X direction from it's original location. The bellows I placed in the HAM3 cleanroom on top of the rack, covered in foil. 

Fil also noticed that the ISCT1 bellows were still open, though hanging down. I took the extra precaution and covered these with foil as well to prevent dust drifting onto the table.

Dust counts during the whole process were 0's or 10's when I looked. This seemed too low so I rubbed my glove above the dust monitor during a sample and counts shot up to the hundreds. I guess that space really is that clean, great!

HAM7 scatter is from SFI2, beam off center on polarizer

Robert, Sheila, Eric, Daniel D

Yesterday morning we were able to identify the source of the scatter in HAM7 as being SFI2, and notice that the beam is very off center on the polarizer on the ZM4 side of SFI2, B:P2.  

We locked the OMC on a single bounce beam with 50W input to the IMC, and turned on the ISS second loop, and got 67mA DCPD sum.  With the viewport on the HAM5 gate valve and a 1 Hz excitation of 1000 counts amplitude on ZM5 TEST, we could clearly see a fringe wrapping shelf at 140 Hz.  We used a piece of black glass to block the beam and could see the scatter shelf go away when the black glass was after B:P2 and reappear when the black glass was before the rotator.  

Robert got some photos of the location of the beam on B:P2, it is clearly off center and near the +Y edge of the polarizer aperture.  We attempted to steer the ZMs to bring it close to the center, but we clipped the beam on the aperature attached to B:L2 before we could bring the beam close to centered.  This indicates that this path was aligned with the beam poorly centered on the Faraday.  

OPS Friday Day shift start

TITLE: 12/19 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 9mph Gusts, 5mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.45 μm/s 
QUICK SUMMARY:

• IOT2L table work, disconnecting and moving it
• More HAM7 chamber work
• HAM1 chamber work
• IAS HAM1 support tubes surveying if HAM1 work allows

CHETA build log -- Thursday 12/18

M. Todd, G. Vajente, L. Dartez

---

Thursday 12/18

1. We compared the beam profile that we fit to the modeled beam in that region, as well as what both of these beams look like at the ITM. We were initially very confused so we went back and more carefully placed the optics, taking care of the of and between the lenses in the telescope.
2. It seemed that the astigmatism was much worse than anticipated so we thought about tilting one of the lenses and seeing if we could compensate for the astigmatism. This gave us pretty confusing results, and especially because the fit to the first dataset was yielding non-physical values. For reference, the fit is done by fitting a quadratic to the beam radius squared as a function of z (i.e. w² = a+bz+cz²).
3. After deliberating in the control room, and returning to corroborate the fintrace model with jammt, we came to the conclusion that the telescope model is sensible; however, the measurement that we were taking is not descriptive enough of the beam to understand how the active telescope performs.
4. We finally decided to go in and take out the pick off to get as close of beam profile measurements to the waist of the beam after L2. We then shifted L2 5cm back toward the laser which was closer to the nominal position in the modeled layout. Here are the two plots of those beam profiles with their fits (I used a quadratic allowing M2 to vary, Gabriele has plots of minimized error of a Gaussian beam). L2 5cm further from M1 than the model. L2 close to model nominal position.

OPS Day Shift Summary

TITLE: 12/19 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:

IFO is in IDLE for PLANNED ENGINEERING

Summary of activities today:

• HAM7 Scattered light investigation, IMC locked beam out of HAM5 - IN PROGRESS, scatter found
• HAM1 Continued investigation into JM1/3 OSEM/controls issues - DONE, both JMs working - alog 88599
• HAM2 Move IOT2L away from chamber - TMW
• HAM2 Lock HEPI - DONE
• HAM2 Removal of PEM Support tube plates - DONE
• HAM4 AIP work, pumps on and off - TMW
• South Bay crane pendant work - DONE
• BSC2 Prep work in West Bay cleanrooms and platform - IN PROGRESS, mostly done

LOG:

Start Time	System	Name	Location	Lazer_Haz	Task	Time End
15:57	SAF	LASER	LVEA	YES	LVEA is LASER HAZARD \u0d26\u0d4d\u0d26\u0d3f (\u2022O\u2022)	10:51
15:46	FAC	Tyler and Crane Tech	LVEA	Y	Crane upgrades south Bay	18:33
15:59	FAC	Kim, Nellie	LVEA	Y	Technical cleaning	16:46
16:09	FAC	TJ	LVEA	Y	Dust Monitor 10 Check	16:46
17:22	JAC	Masayuki	Optics Lab	N	JAC Work	19:18
17:35	FAC	Kim	MX	N	Technical Cleaning	18:32
17:40	SQZ	Sheila, Robert	LVEA	Y	Hunting for scattered light	19:35
17:46	PEM	Jim, Randy	LVEA	Y	PEM Support Tube Plate Check	18:15
17:51	SQZ	Eric, Daniel	LVEA	Y	Scattered light checks	19:35
17:57	TCS	Matt	Vac Prep Lab	N	Cheeta	19:09
18:17	SQZ	Jennie	LVEA	Y	HAM7 work	18:30
18:29	ISC	Betsy	Optics lab	N	Checks	19:18
20:44	ISC	Betsy	LVEA HAM1	Y	Open light pipe, HAM1 work	22:37
20:56	FAC	Crane contractor	LVEA	Y	Crane inspections	00:55
21:08	SQZ	Daniel, Eric, Kar Meng	LVEA	Y	HAM 7 OPO	00:03
21:09	PCAL	Tony	PCAL	N	Transfer Meas.	22:30
21:09		Keita	LVEA	Y	Checking in with Betsy	21:37
21:15	FAC	Randy	LVEA	Y	Checking on crane man	21:42
21:17	IAS	Jason	LVEA	Y	FARO Work BSC2	23:17
21:20	IAS'	Ryan C	LVEA	Y	FARO BSC2	23:20
21:29	TCS	Matt	Vac-Prep Lab	N	Cheeta\\	00:07
21:48	PSL	Jean-Rene, Alicia	LVEA	Y	PSL Camera disconnect	01:46
21:50	ISC	Richard	LVEA	Y	Check on activities	23:42
21:55		Masayuki	LVEA	N	Beam dump assembly	22:37
22:03	SQZ	Sheila	LVEA	Y	HAM7 OPO	00:00
22:53		Richard	LVEA	Y	Checking on activities	23:41
22:57	FAC	Tyler	LVEA	Y	Crane upgrade wrap up	23:09
23:09	SUS	Rahul	LVEA	Y	HAM1	20:09
23:25	FAC	Richard	LVEA	N	Checks	00:07
23:28	PCAL	Tony	PCAL Lab	N	Setting up a measurement	22:28
23:37	SEI	Jim	LVEA	Y	HAM2 HEPI	00:06
00:07	ISC	Keita	LVEA	Y	Opening Light Pipe	02:07
00:24	JAC	Jennie	Vac-Prep Lab	N	Putting stuff away	01:24
00:35	SQZ	Daniel, Eric	LVEA	N	HAM7 Work	01:35

HAM7 Realignment progress

[Daniel, Kar Meng, Eric, Sheila]

This afternoon, we continued with the realignment of the VIP after the VOPO swap.  When we first started, we briefly lost the CLF input alignment between the fiber and the VOPO cavity.  It turned out that the collimator was loose in the mount.  We took out the collimator holder and noticed that the 2nd grub screw hadn't been tightened all the way.  After fixing, we realigned the cavity till we could see a reasonably strong beam in transmission while the cavity was scanning.  

We then began the painful process of aligning the weak transmitted beam through the various components in HAM 7.  Using only the first steering mirror between the VOPO and SFI1 on the VIP, we managed to get the beam roughly aligned up to FC1.  However, we couldn't quite figure out how to get the return beam from the filter cavity retroreflected through SFI1 again.  We eventually decided to move FC1 a bit to get the beam back through SFI1, through SFI2, and onto the iris right before ZM4.  We're thinking of doing the following to finish the alignment process:

• Walk the alignment a bit more to get to the beam diverter and onto the 1064 trans PD on SQZT7
• Optimize the alignment of the seed to the VOPO using the PD
• Dither lock the seed and finish aligning the SQZ path on HAM 7 with the brighter beam.  We will need to revert the FC1 alignment at some point.  Initial settings before we started tweaking things:  
  • H1:SUS-FC1_M1_OPTICALIGN_Y_OFFSET = - 153
  • H1:SUS-FC1_M1_OPTICALIGN_P_OFFSET = 232 

HAM1 vent work - JM1 and JM3 plugged in to the electronics chain - OLC re-taken and offsets applied on the medm screen

Betsy, Rahul

We found that SUS JM1 had a faulty quadrupus cable, which we replaced it today. Next, I took OLC for both JM1 and JM3 in HAM1 chamber. I applied the offsets, gains and then centered the BOSEMs - and they look good. Next, I will start checking the health of the electronics chain and the suspension itself (i.e. by taking the transfer function measurements).

The offsets and gain for JM1 is recorded in this screenshot - accepted in the SDF (safe).

The offsets and gain for JM3 is recorded in this screenshot - accepted in the SDF (safe).

HAM1/2 beam positions with 2W (Betsy, Keita)

For the upcoming ISS array swap, we plan to bypass the IMC, which is known to be a pain, but we need a stable beam for the array alignment.

Once the corner volume is vent, we use the QPD on the old array and IMC-IM4_TRANS as the initial reference for bypassing the IMC. Once IMC is bypassed, we will center REFL WFS BEFORE removing the old array and record the RM1/RM2 PIT and YAW. This way, even if we somehow suspect e.g. the pointing of the beam going to the IM4 moved after removing the old array, we can still restore the pointing by looking at the REFL WFSs in addition to IM4.

We measured the beam positions on these QPDs today even though we'll repeat this later.

IFO configuration:

• IMC was locked with 2W.
• REFL beam diverter was closed so no light comes out. (POP bdv was also closed just because.) 
• The cover on the REFL septum window was removed.
• PRM, all IMs and RMs are aligned. (Watchdog of RMs were reset.) ITMs are misaligned.

Arrow ("->") means before and after the REFL centering servo (DC1 and DC2) was turned ON:

	PSL-ISS_SECONDLOOP_QPD	IMC-IM4_TRANS	ASC-REFL_A_DC	ASC-REFL_B_DC	SUS-RM1-M1_DAMP INMON	SUS-RM1-M1_DAMP INMON
PIT	-0.814	0.366	-0.884 -> 0	-0.995 -> 0	293 -> 168	-363 -> 68
YAW	0.655	-0.146	0.590 -> 0	0.220 -> 0	-176 -> -214	277 -> -70

Septum cover is left OFF but the PSL light pipe was closed after this. REFL centering was turned off but I didn't bother to offload the ASC output to RM sliders.

REFL WFS nubmers as of now are not super meaningful as we'll still have to lock HAM2 down, which potentially change the relative alignment between HAM1 and HAM2. (But it's good that the beam is still hitting REFL WFSs after HAM1 was locked down even though Jim noted that the ISI position of HAM1 is not good. )

I'll open the light pipe tomorrow and quickly repeat the measurement after Jim locks down HAM2 HEPI.

Vent activities in HAM 1 for the Jitter Attenuation Cavity (JAC work)

Betsy, Fil, Rahul

Today we kicked started the installation activities in HAM1 chamber for the Jitter Attenuation Cavity (JAC). Given below are the things we placed on the ISI table - they are all roughly positioned and dog clamped. 

1. Tip Tilt JM1 - now connected to electronics chain, having some issues with the bosem adc counts etc, will continue looking into it.

2. Tip Tilt JM3 - now connected to the electronics chain, bosem centered, will proceed for health checks once the chassis and electronics chain looks okay.

3. The two periscopes for the JAC, Type 121 and 132 - assembly report posted by Jennie - 88574.

4. Some optics on Siskiyou mount were also added to the table.

I am attaching pictures which shows the above mentioned things added to the table - and for comparison a picture showing before any addition was (here) made.

Fil also performed group loop checks on JM1 and JM3 and did not find any issues with them.

HAM1 iris installation

[Jason, Betsy, Masayuki]

Two arises are installed into HAM1 chamber. They will be used as the alignment reference for new PSL modematching lens installation.

• Assembled a Thorlabs ID12 iris mounted on a 0.5-inch post with a post holder and BA2 base.
• The assembled iris was temporarily placed inside the chamber and secured with a dog clamp.
• Transitioned to laser hazard.
• Performed rough alignment using a sensor card, followed by fine alignment with an IR viewer, to center the beam through the iris.
• The beam path is offset by ~+5 mm in the +y direction from the ISI design center; this is not considered a significant issue.
• The iris location is marked with a blue circle in the attached figure.

Next step: move to the PSL and install the new mode-matching lens, likely tomorrow. This will break the IMC mode matching; IMC relocking will not be possible until the JAC installation is completed.

Relay Tube Removed to Install Viewport Assembly

(Jordan, Travis, Gerardo)

The relay tube connecting HAM5 and HAM7 was removed.  We had a few snags while removing it, for some reason the space between bellows is tight, perhaps due to the difference between pressure states, one chamber is under vacuum the other is not.

After the tube was out, the viewport was installed on a short assembly, the viewport and the entire assembly was leak checked and no leaks were found.  He background a the leak detector remained at 1.0x10^-10 torr*l/sec during the leak testing.

System is currently being pumped down via a small turbo plus an aux cart.

Old OPO inspection after the swap from HAM7

[Eric, Daniel, Karmeng]

We transferred the OPO from LVEA to optics lab, uncovered the lids and everything looks good.

Touch the mirror mounts and mirrors, no failure except for M3, which swivels off the mount, only part of the glue holding the mirror on the mount.

Thurs DAY Ops Summary

TITLE: 12/04 Day Shift: 1530-0030 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY:

After CDS & H1-Locking work of yesterday, today we transitioned to starting prep work for the upcoming vent of HAM7.

However, there was more CDS work today which was related to ISC Slow Controls....but in the middle of this...

There was a 90min power outage on site!!
 

LOG:

• early-1615 Randy was at the FCES putting stickers on items
• 1539-1900 pre-vent technical cleaning begins (kim.nellie)
  • 1716 SR3 + HAM5 tripped; gave it some time, untripped/redamped @1805
• 1545 SEI_ENV transitioned to MAINTENANCE for vent
• 1609 TCSx Laser off (TJ contacted; prob due to cleaning near the rack)
• 1624-1745 BSC2 platform & then sorting parts (randy)
  • Tripped BS, ISI, HEPI---leaving tripped until randy finishes in about an hr
  • Once he was done, BS was taken to ALIGNED & SEI_BS taken to DAMPED_HEPI_OFFLINE
  • 1745-1845 Sorting through rail parts in North Bay
• 1626 quick assistance for cleaning (chris)
• 1628-1635 lvea walkthru (richard)
• 1630 cer to pull slow control chassis for ISC (fil)
  • This affects a PZT for the IMC, so it lost lock.  Keeping IMC_LOCK at OFFLINE during this beckhoff work.
• 1718-1810 Unboxing the JAC in the optics lab (jennie, jason)
• 1728 Taking Integrating sphere (had been at KAGRA) into PCal Lab (tony)
• 1730-1855 Grabbing parts at offsite vendor (mitch)
• 1751-1900 Building 2nd CHETA enclsure in the CHETA/JAC Lab (matt)   
• 1803-2012 OPO Testing cont (KarMeng.Eric)
  • 1812 Shiela joining but will be in/out with them + looking for parts
• 1813-1820 chamber measurements for JAC (jason)
• 1814 Kobelco (purge air compressor) being turned on (travis,jordan)
• 1848-2000 Inventory work at EX + EY (randy)
• 2005 Grabbing wipes in Cleaning Room (ibrahim)
• 2023 CHETA Viewport part search (gerardo)
• 2025 Power Outage ON Site!
  • Ended up down for over 90min
• See oli's alog for a summary of recovery.

With voltage set to 0, grounding of the ITMX ESD driver

[Joan-Rene Merou, Alicia Calafat, Sheila Dwyer, Jenne Driggers]

We have entered the LVEA and went to the Beer garden. There, we first turned off the Low Voltage ITM ESD Driver D1600092, first the 15V switch and then the medium voltage switch. In order to turn it on again, it should be reconnected in the opposite order. With the voltage request set to 0 and chassis powered off, we have unplugged the SHV cables going to the chamber and plugged into Robert's ground boxes, which we used to ground to the rack which is grounded to the chamber. This has been done at both drivers (See attached photos).

Afterwards, we have changed the code at /opt/rtcds/userapps/release/isc/h1/guardian/ISC_LOCK.py in order that the LOWNOISE_COIL_DRIVERS will go to LOWNOISE_ESD_ETMY instead of TRANSITION_FROM_ETMX. This has been done by changing lines 6670 and 6674, moving the ", 15" step from line 6670 to 6674. Finally, we communicated the change to the operator and loaded the guardian.

It appears that the grounding did not decrease the amplitude of the combs. As seen in the attached figure, the relative amplitude of the first harmonics of the combs remains mostly the same before and after the change on November 13th.

ISS array S1202965 was put in storage (Rahul, Keita)

Related: https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=87729

We disconnected everything from the ISS array installation spare unit S1202965 and stored it in the ISS array cabinet in the vac prep area next to the OSB optics lab. See the first 8 pictures.

The  incomplete spare ISS array assy originally removed from LLO HAM2 (S1202966) was moved to a shelf under the work table right next to the clean loom in the optics lab (see the 9th picture). Note that one PD was pulled from that and was transplanted to our installation spare S1202965.

Metadata for both 2965 and 2966 were updated.

ISS second array parts inventory https://dcc.ligo.org/E2500191 is being updated.