Closes FAMIS#39855, last checked 89138

Corner Station Fans (attachment1)
- All fans are looking normal and within range.

Outbuilding Fans (attachment2)
- All fans are looking normal and are within range.

Richard asked for a one-day trend of the dust monitor at BSC2 since he moved it from the floor up to the dome platform (alog89137); see attached. Heightened counts from today likely from cable pulling activities around/on top of HAM3 nearby.

Today Randy T and I ran power for the Cross Flow HEPA fans on the platform around BSC2.  The fans are on and turned down to low at the moment.  We also moved the dust monitor from the floor to the platform to monitor dust counts to have a better understanding before pulling the dome.

Last Checked Jan6 (alog 88698).

NOTES:

• LAB2 looks OFF (noted last back in Sept)--will send a note to RyanC on this one.
• PSL 101 & 102 (0.5um particles) pretty much zero the last month, but do have 10min of 10 counts a couple times.
• DR1  (0.5um particles) also pretty much zero the last month, but has had some dust counts 3x in the last month.

In the control room, the alarm handler was complaining about opticsd lab dust monitor.

It seems that it surged up and stayed there for about half an hour. I acknowledged the alarm (the dust conts are already back to normal, it seems).

Not sure what happened but this seems to happen kind of regularly.

Closes FAMIS#39852, last checked 88845

Corner Station Fans (attachment1)
- MR FAN1_170 has been relatively loud since it was turned on on Tuesday.
- All other fans are looking normal and within range.

Outbuilding Fans (attachment2)
- MY FAN1_270_1 is quite noisy, but since it's at the midstation I think that's okay
- All other fans are looking normal and are within range.

Summary: Scattering studies before the end of O4 suggested that the non-linear vibration coupling that dominates DARM at 20 Hz and contributes significantly up to about 50 Hz, was produced by modulated retro-reflections of the annular beams coming from the bevels of the ITMs and the annular beams from the BS barrel and cage (87758).  End-of-run studies, reported here, support these conclusions, and a model estimating scattering noise from vibration time series suggests that reflection from the SR tube MC baffle near HAM4 is also a likely ambient noise source in the unusually high 80-200 Hz region of DARM. The annular beam noise from chamber walls would be mitigated by the already planned ITM cage baffles and the BBS. It is also likely that the HAM4 and SR MC baffle noise would be mitigated by the BBS. The safest route would be to go ahead and install the HAM4 table baffles and treat the HAM4 MC baffle, but we could also wait and see if their noise is mitigated by the BBS.

Noise at 20-50 Hz injection frequencies, likely from 20 and 45 degree annular beams

As noted at the end of alog 87758, the noise in DARM was most consistent with the motions of permanent accelerometers on ITMX, ITMY and the BS, consistent with what would be expected if the annular beams (83050) from optics in these chambers cause scattering noise. We have, since then, mounted temporary accelerometers around these chambers and elsewhere to further test this hypothesis, particularly placing accelerometers on the vacuum envelope at locations just outside of where the annular beams hit the inside of the enclosure.

We used two of the three vacuum enclosure techniques mentioned in 87758, the beating shaker technique and a variant of the consistency test for sweeps from shakers at different locations. However, we were not able to use the third technique, the hand-held shaker test in the region close to the vertex because of magnetic coupling, likely to magnets on the BS, even though the coil is much smaller than those in our other magnetic shakers.

Consistency technique

The accelerometers that were most consistent for 3 sets of 3-shaker injections were temporary accelerometers mounted near where the ITM annular beams hit the bellows of the spool pieces between the ITMs and BSC2, one for each ITM, and the permanent accelerometers “BSC3_Y” and “MCtube”. The BSC3-Y accelerometer is near where the annular beam from the BS likely shines (See Figure 1), but the MC tube accelerometer is probably coincidental because when a shaker was moved to the MC tube, the accelerometer there was no longer consistent with DARM.

Beating shaker technique

The accelerometers mounted just outside where the ITM annular beams hit were also the most consistent with DARM for the beating shaker technique. Figure 1 shows results of one of the most convincing beating shaker tests. A piezo shaker was mounted near where the ITMX annular bevel beam hits the bellows of the BSC2-BSC3 spool-piece (see photograph here ). A second shaker was mounted on the old H2 BSC7. The shakers were set to 31.005 Hz and 31 Hz respectively. The amplitudes of the two shakers were adjusted so that each individually produced the same amplitude of peak in DARM, before they were both turned on. Figure 2 shows that the timing of the beat envelope of the accelerometer on the bellows where the annular beam hits, matches the beat envelope timing in DARM, while timing for 14 other accelerometers that I examined (7 are shown) did not match as well. Also, the modulation depths of the beat in the accelerometer signals are greatest in this region of the enclosure, indicating that the two shaker peaks have similar amplitudes in the accelerometers near this location, like the two peaks in DARM (by adjustment). 

Potential noise at 80-200 Hz from MC baffle in SRtube near HAM4

Early in O4 we found that the MC baffles in the input arm were causing noise in DARM (74175). We fixed this by angling the baffles further (76969). We also found that the MC baffles in the output arm could make scattering noise but that this was at a lower level than the baffles in the input arm (74175).

During recent end-of-run studies, I shook the output arm to asses the current status of scattering noise from these output arm baffles. The injections made noise in DARM but It was difficult to determine whether injection-free ambient vibration levels would affect DARM, because the noise increased with frequency rather than forming a flat shelf, I think due to the optical transfer function of scattering noise from the SR cavity back into the interferometer (LIGO-T060073).  So I included a "BSSR" optical transfer function in my new model which combines accelerometer and seismometer time series to estimate the phase noise and radiation pressure noise from a source at any point in time (scattering noise, like the underlying vibration, often varies greatly in time). I was able to match the time evolution of the scattering noise in DARM during the vibration sweep by filtering external accelerometer data using resonant gains to simulate the resonances of the internal baffles. I used two resonances at 13.2 and 14.2, with Qs in the hundreds to simulate the DARM response - the results are shown in Figure 3.

However, the Qs that were needed seemed too high because Corey and I had tried to damp these (39156), and the only evidence that the source was the baffles was the low resonant frequency, consistent with the measured frequency of input arm MC baffles.  But the low frequency resonance might also be a resonance of the vacuum enclosure itself, so I decided to get the Qs and resonant frequencies from the baffles directly, using a laser vibrometer. I found that The MC (eye) baffle by HAM5 has a resonance of 12.1 Hz, the MC Baffle by HAM4, at 13.3 Hz, and the SR tube has a resonance at 14 Hz. Thus, based on the 13.2 and 14.2 Hz frequencies that made the original model reproduce DARM noise, the likely source of the scattering noise is the eye baffle by HAM4.  Using the measured Qs, resonances, and a simplified mechanical transfer function from the permanent accelerometer that was present when I did the original sweep to an accelerometer that I mounted last week right outside the baffle, I got the results shown in Figure 4 (the permanent accelerometer I used for Figure 3 underestimated tube motion at the location of the baffle which was why I had to use such high Qs - the measured Qs were 5 and 10, more consistent with our damping). The predicted level of noise in DARM for ambient vibration levels in Figure 4 is slightly lower than the more naive model of Figure 3, getting as close as a factor of 3 below the current noise floor in the 80-200 Hz region.

One possibility is that the eye baffle is reflecting light in the 45 degree annular beam coming from the BS. Based on the evidence for this in Figure 5, and the increasing evidence that the annular beams are bright enough to be problematic, I would guess that there is about an 80% likelihood that this is the source of the SR tube noise and that the Bigger Beam Splitter would mitigate this noise source. This was also my assessment for the noise produced by shaking the HAM4 table (87758), and I suggested that we could wait until after the installation of the BBS, and then mount table baffles if the noise had not been mitigated. I think this would also be a reasonable path for the eye baffle, waiting to see if the noise goes away with the BBS, and improving the baffle if it does not. Of course the safest path would be to mitigate the MC baffle(s) and install the HAM4 table baffles anyway. If we do mitigate the MC baffle(s), I would want to remove or treat the central portion of the baffle(s), as well as, or instead of, increasing the angle of the baffle(s) like we did in the input arm. This is because the reflection site, as evident in Figure 5, is likely to be in the central region of the baffle.

-Robert, helped especially by Sam and Joan-Rene

Closes FAMIS39851, last checked in alog88771

Everything looks as it did during the last check, no real changes over the past week that I can see.

For FAMIS #39850: All fan trends look nice and flat.

Closes FAMIS#27662, previous check in alog84918. No new issues with any dust monitors.

**PSL Anteroom and Laser Room will be done at a later date when going in there is required for other tasks by Ryan Short.**

For the CS dust monitors.

LVEA: 

HAM1 / LVEA5: On the +Y side of the HAM1 CR. Passed the zero count on the first round, and the flow was 2.8. PASS

HAM1: An additional spare DM on the -Y side of the HAM1 CR. Passed the zero count on the first round, the flow was a bit high at 3.0 so I adjusted it down to 2.8. PASS

HAM7 / LVEA6: Passed the zero count on the first round, and the flow was 2.8. PASS

Biergarten / LVEA10: Passed the zero count on the first round, and the flow was 2.8. PASS

DR: This DM was frozen when I got to it. Passed the zero count on the second round (first round had 2 cts of 0.3 um), and the flow was 2.8. PASS

Optics Lab: Passed the zero count on the first round, and the flow was 2.8. PASS

VPW: Passed the zero count on the second round (first round had 1 ct of 0.3 um), and the flow was 2.8. PASS

CER:

All the old grey HHPC handheld dust monitors in various states of degradation, none of them can take a full sample on power or battery without dying. I've removed the last one of this model I found in the CER and added it to collection of the other broken ones.

I tested the last spare GT521s left in the CER as well which I had borrowed from the FCES (s/n R16420). It passed the zero count test on the 2nd round (first round had 1 ct of 0.3 um) and the flow is 2.8. PASS

For the OUT building dust monitors.

EY: Passed the zero count on the second round (first round had 1 cts of 0.3 um), and the flow was 2.8. PASS

EX: Passed the zero count on the second round (first round had 1 cts of 0.3 um), the flow was a little low 2.65 so I went to adjust the pump in the mechanical room. These new vacuum pumps' adjustment knob seem touchier than the old one. It was at 19.5 inHg, I adjusted it up to 20 but it would stay at 20, it kept slowing increasing in pressure. I watched it slowly build up to almost 22 after I adjusted it up slightly to 20. I ended up bringing it back down to as close as I could get to where it was. I ended up around 19.8 inHg which brought the DM flow back to a little over 2.7, within the 5% margin of error. PASS

Closes : Famis 27647 Using Vibration Sensors To Gauge Health Of HVAC Fans. 

Vibrometers look fine and don't seem to be abnormally performing yet. 
 

FAMIS 37260, last checked in alog88278

Couple of peaks over the past few days which might correspond to high winds, but otherwise these look good for the duration including the holiday break and vent work.

I made a new medm screen for the dust monitors so there's a single screen where you can see all of the particle counts for the site, and you can get to all useful dust monitor screens through this screen. I also added some shell command buttons to launch scopes of the individual DMs. Its located under PEM on SITEMAP.

Closes FAMIS 27648, last checked in alog 88314

Trends look fine!

J. Kissel

Post Dec 4th power outage, we've have an EPIC week of windstorms that have inhibited recovery effort, which has delayed upgrade progress. The summary pages (on their 24 hour cadence) and the OPS logs / environment summary don't really convey this well, so here's a citable link to show how bad last Friday (12/05), Monday (12/08), and Wednesday (12/10) were in terms of wind. Given the normal work weekend, it means that we really haven't had a conducive environment to recover from even a normal lockloss, let alone a 2-hour site-wide power outage. 

The attached screenshot is of the MAX minute trends (NOT the MEAN, to convey how bad it was) of wind speed at each station in UTC time. 
The 16:00 UTC hour mark is 08:00 PST -- the rough start of the human work day, so the vertical grid is marking the work days.
The arrow (and period where there's red-dashed 0 MPH no data) shows the 12/04 power outage.
The horizontal bar shows the weekend when we humans were trying to recover ourselves and not the IFO.

I restarted all the dust monitor IOCs, they all came back nicely. I then reset the alarm levels using the 'check_dust_monitors_are_working' script.

WP12901. Daniel, Jeff, Oli, Fil, Marc, Jonathan, EJ, Tony, Dave:

Summary:

Yesterday I replaced h1iscex's 18bit-DAC with a 20bit-DAC as part of the project to eliminate all 18bit-DACs from production. There is currently no indication that the 20bit-DAC is driving the AI chassis with any voltage, investigation is ongoing.

Details:

The 18/20 bit DACs use the same interface card, so for the upgrade I was able to pull the IO Chassis out half way with cables still attached to access the PCIe bus. I removed the old 18bit-DAC and replaced it with on of the 20bit-DACs from h1susex upgrade

I do not know if the 20bit-DAC from h1susex was the one driving the PI or the one which had been idle since the LIGO-DAC went in mid 2024.

The original interface card and ribbon cable were reused. No field cabling was disconnected, no AI chassis were powered down.

Upgrade was done between 12:00 and 13:00 Tue 02dec2025.

Later that afternoon Tony found that the PCAL readbacks were not responsive. Tony and I went to EX around 17:00 to verify the 20bit-DAC was installed and connected correctly, it was.

This DAC has a special AI Chassis, D1101785 "aLIGO 18 Bit AI Chassis" which has handy BNC pickoffs for all 8 channels. We put a scope on the two channels being driven by h1calex (6,7) and could see no signal.

Also the last channel on the AI is loop-backed to the first ADC AA chassis with a DB9 cable, and the IOP is configured by SDF to drive the duotone from DAC0-chan7 back to ADC0-chan30. No signal is seen there either since the upgrade.

h1pemex was upgraded from an 18-bit to a 20-bit DAC today, so we needed to make sure we had a calibration correction. The new filter banks that Jeff had put in (88321) for the calibration correction are called H1:PEMEX_EX_DACOUTF_1, H1:PEMEX_EX_DACOUTF_2, H1:PEMEX_EX_DACOUTF_3, and H1:PEMEX_EX_DACOUTF_4. I installed a filter called 20BitDAC that was a gain(4) in FM10 of each of these filter banks, loaded them in, and turned them on along with the input/output/gain of the filter banks. I've accepted these changes in sdf safe