Thu CP1 Fill

Thu May 08 10:12:38 2025 INFO: Fill completed in 12min 34secs

Gerardo confirmed a good fill curbside.

Morning Purge Air Checks 5-8-25

Dry air skid checks, water pump, kobelco, drying towers all nominal.

Dew point measurement at HAM1 -43.7 °C.

CDS environment EPICS IOCs now running on cdsioc0 under puppet management

I have created puppet rules to run each Geist ENV EPICS IOC as a systemd service on cdsioc0 (during testing they were being ran by hand on opslogin0). All of these services are now operational.

BTW, there is a new ENV overview MEDM which can be opened by clicking inside the ENVIRONMENT section of the CDS Overview, please see attachment.

ISC Alignment Work, Day 6 in HAM1 (May 7th): 20W now into IMC, POP beam profiles done.

Oli, Keita, Elenna, Jennie, Sheila, Ryan S, Rahul, Betsy, Camilla

Day 1: 84193, Day 2: 84228, Day 3: 84230 and 84239, Day 4: 84274, Day 5: 84292

• To work on REFL beam: need PRM aligned and ITMX or ITMY misaligned 
• To work on POP flashes: need PRM aligned and ITMX aligned
• To work on POP single bounce (low power ~30uW into HAM1 POP path for 20W from PSL): need PRM and ITMY misaligned 

In the morning Keita and Jennie aligned the POP flashes on the periscope mirrors and M10 dichroic. The height of this beam is 3.75" on these mirrors to account for the ALS green beam being 13mm above the POP beam. Keita was a little concerned about the height of the top periscope mirror so we'll need to check the green ALS beam carefully on this and if it 's near clipping we may need some in-vac pico-ing.

Rahul then moved PM1 to it's final position. Elenna and Rahul checked that the signed of the PIT and YAW sliders were correct. 

Shiela, Rahul and I then worked on centering the beam on PM1 and L2 without the 90/10 M12 in place, so that we could later have enough power to beam profile the POP single bounce beam. To get the beam height back up to 4" at PM1, Rahul needed to pitch PM1 mechanically. 

Oli then increased PSL input power to 20W, we aligned to POP single bounce and Sheila and I took beam profile measurements before PM1 and after L2, details in 84307.

Elenna, Rahul and I then replaced the 90/10 M12 and recentered the beam on PM1 and L2. We started aligning the POP air path but aren't happy with it, dumped the beam and will continue to work on. 

Betsy let in the PSL ALS beam into HAM1 by opening the light pipe and I dumped it straight away. See 84312.

Today we plan to: align the POP, REFL and PSL ALS beams out of the chamber, open the X-arm check the green ALS beam alignment on the shared optics and off the table, including rolling up ISCT1 and adding the VP simulator. The POP LSC/ASC diodes and all beam dumps still need to be aligned and checked. 

OPS Thursday day shift start

TITLE: 05/08 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: LIGHT_MAINTENANCE_WINDY
    Wind: 10mph Gusts, 4mph 3min avg
    Primary useism: 0.03 μm/s
    Secondary useism: 0.13 μm/s
QUICK SUMMARY:

• More HAM1 aligning, EX wind fence
• THUR - X-ARM PEEK - GV open for ~a day

HAM1 PSL ALS beam in chamber now

Gearing up to align the 1 PSL ALS beam mirror in HAM1, we opened the ALS shutter. Camilla immediately found the beam and dumped it into a v-dump to align tomorrow. This shutter will stay open for a couple days while we finish alignment of this path alongside the other paths.

Ops Day Shift Summary

TITLE: 05/07 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Lots more progress today; PM1 is in place and EX wind fence work is going well.
LOG:

Start Time	System	Name	Location	Lazer_Haz	Task	Time End
15:07	SAF	LVEA is Laser HAZARD	LVEA	YES	LVEA is Laser HAZARD	Ongoing
14:50	FAC	Kim, Nelly	LVEA	-	Technical cleaning	15:15
14:51	FAC	Ken	LVEA	-	HAM4/5 cable trays	22:51
15:55	AOS	Betsy	LVEA	-	Talking to Ken	16:13
15:56	FAC	Kim	H2	N	Technical cleaning	16:11
16:14	VAC	Gerardo	LVEA	-	Talking to Ken	16:30
16:32	ISC	Keita, Jennie	LVEA	YES	HAM1 alignment (Jennie out @ 18:59)	19:31
17:01	EE	Fil	LVEA	-	HAM1 racks	18:38
17:05	SEI	Jim, Mitchell, Randy, Tony	EX	N	Wind fence work	19:03
17:11	EE	Jackie	FCES	N	Measurements	19:11
17:45	VAC	Travis, Tyler	MY	N	Moving equipment	19:20
18:14	FAC	Nellie	EX	N	Tech clean	18:46
18:34	VAC	Gerardo	LVEA	-	Isolating OMC turbo	18:42
19:08	ISC	Daniel	LVEA	-	ISC rack cable istallation	20:21
19:13	SUS	Rahul	LVEA	-	PM1 install	20:46
19:13	ISC	Camilla	LVEA	YES	HAM1 POP path alignment	Ongoing
19:31	CDS	Dave	MY	N	PEM sensor electronics	20:01
19:35	ISC	Sheila	LVEA	YES	HAM1 POP path alignment	22:20
19:55	ISC	Elenna	LVEA	YES	HAM1 POP path alignment	20:56
20:05	SEI	Jim, Randy, Mitchell	EX	N	Wind fence work	21:46
20:14	FIT	Ibrahim	Y-arm	N	On a walk	20:54
20:29	ISC	Keita	OptLab	N	Looking at spare Siskyou mount	20:58
20:32	CAL	Tony	PCalLab	Local	Start measurement	20:38
20:42	ISC	Oli	LVEA	-	Unlocking rotation stage	20:51
21:26	VAC	Travis	MY	N	Roughing pump work	22:19
21:37	PCAL	Tony	PCAL Lab	Y(local)	Getting stuff to ship to France	21:37
21:39		Betsy	LVEA	YES	Seeing if HAM1 team needs help	22:03
21:50	SUS	Rahul	LVEA	-	PM1 adjustments	23:03
22:13	ISC	Elenna	LVEA	YES	HAM1 POP path alignment	Ongoing
23:03	AOS	Betsy	LVEA	-	Checking on HAM1 team	Ongoing

HAM1 POP path beam profile and distance measurements

location number on drawing	distance	horizontal 13.5% diameter [um]	vertical 13.5% diameter [um]	photo of profiler location	photo of profiles	photo of beam scan measurements
1	52 mm from dichroic M10	6243	64040	here and here	9022	9023
2	147 mm from dichroic M10	6202	6365	9028	9026	9027
3	119 mm from HR of 50/50 BS M15, also 295mm from center of lens L2	870	874	9031	9030	9029
4	153 mm from HR of 50/50 BS, approximate location of LSC diode	279	284	9035	9032	9033
5	128 mm from HR of 50/50 BS	721	726	9036	9037	9038
6	139 mm from HR of 50/50	483	490	9041	9040	9039
7	353 mm from HR of 50/50 BS	3280	3372	9042	9043	9044

Camilla made these measurements with 20W input power into the IMC, PRM and ITMY misaligned single bounce beam.  We didn't place the 90/10 BS M12 in the pop path yet so that we would have about 35uW to measure beam profiles. There's a rough pen sketch of where these locations are in this photo.

Camilla also made ruler measurements of some distances:

• PM1 to 50/50 BS M15 is 405mm
• PM1 to center of L2 is 229 mm
• center of L2 to M15 is 178 mm
• dichroic M10 to PM1 is 360 mm
• bottom of periscope  (M8 or M9) to dichroic M10 482mm
• HR side of M15 (50/50 BS) to front of LSC diode box is 158 mm, diode itself is 3 mm proud of diode box.

HAM1 Wednesday

Morning (JennieW, Rahul, Keita)

We used the PRX flashes to align the POP path.

POP periscope location is good but the drawing is not.

The POP periscope position, which was set yesterday by Camilla and others, was right. That means that the drawing on D1000313-v19 is wrong. The periscope in reality is about an inch toward -Y direction relative to D1000313-v19. See the first picture, which was shot with a cellphone inserted under the top periscope mirror and looking straight down the bottom mirror. This means that the dichroic (M12) needed to be shifted by the same amount too.

Since the distance betwen the IFO and the lens for POP WFS doesn't matter that much, everything downstream (i.e. 90:10, PM1 tip-tilt, a lens, 50:50 and POP LSC as well as POP WFS) will be installed using the drawing.

We mainly rotated the periscope mirror clamps around the post for rough alignment, but we might have changed the mirror height by a millimeter or two in the process. 

PM1, which is calld that because it's the 1st (and the last) suspended Mirror for POP, is somehow called RM3 in D1000313. Systems please fix it.

Set the IR beam spot height/position on the periscope as well as the dichroic

The IR beam is supposed to be about 6mm or 1/4" lower than the center line of both of the periscope mirrors as well as the dichroic. This is because the green ALS beams are supposed to be ~13mm higher than IR. See L1200282 “CPy-X, CPx-Y” case on Table 1.

Top Periscope Mirror

It was almost impossible to see how much the beam is lower than the center of the top and bottom periscope mirror. Using the IR viewer card, I and Jennie agreed that the beam is lower than the center, but we could not quantitatively say how much especially on the top. We'll leave it as is, and if the green beam from the end station is too high we will have to use pico because we periscope is already as high as possible.

Bottom peri mirror

If everything is as intended, the bottom periscope mirror is 4" high from the ISI surface and the POP beam is 1/4" lower than that, therefore the POP beam is (1-0.25*sqrt(2)) = 0.646" = 16.4mm away from the bottom edge of the mirror.

Using a ruler in chamber (and measuring the dimensions of a spare Siskiyou mount using caliper), the height of the bottom periscope mirror center was calculated to be ~4.07" from the ISI surface, i.e. 0.7" too high. This means that, when the beam height measured from the ISI is as designed (i.e. 4"-1/4"), the POP beam is (1-(0.25+0.07)*sqrt(2))=0.547"=13.9mm away from the bottom edge of the mirror.

If you have difficulty understanding this, see the cartoon.

POP beam radius is ~2mm, so 13.9mm (or even 13mm for that matter) looks like a safe distance to me. I don't see the need to readjust the height of the bottom periscope mirror.

I adjusted the top periscope mirror to set the beam height right after the bottom peri mirror to be ~3.75" using the IR viewer card and a ruler.

Dichroic

I placed the dichroic about 1" into -Y direction relative to the drawing (because I had to), and used the bottom periscope mirror to set the beam height close to the dichroic to be ~3.75".

Then I used the dichroic to steer the beam into the direction of the location for PM1 without placing 90:10.

For the beam profile measurement, the downstream alignment is done without 90:10. Later we will install 90:10 back in place and do the final alignment.

Estimating surface defocus of test masses and absorption from HOM spacing

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.

Parameter	Value	Notes
alpha_x,i	430 ppm	from alog 76937
alpha_y,i	375 ppm	from alog 76937
alpha_x,e	0 ppm
alpha_y,e	0 ppm
P_y,i_rh	0.000 W	T0 = 1417899757
P_x,i_rh	0.850 W
P_x,e_rh	1.950 W
P_y,e_rh	2.146 W
P_yarm	385159 W	T0 = 1417899757
P_xarm	385159	T0 = 1417899757
Gx	0.8149	T0 = 1417899757
Gy	0.8198	TMS * pi G    =   cos2 (   ----------------   )                       FSR
Ai_y	-26 uD/W
Ai_x	-39 uD/W

---

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.

Parameter	Value	Notes
alpha_x,i	430 ppm	from alog 76937
alpha_y,i	375 ppm	from alog 76937
alpha_x,e	200 ppm
alpha_y,e	210 ppm
P_y,i_rh	0.000 W	T0 = 1417899757
P_x,i_rh	0.850 W
P_x,e_rh	1.950 W
P_y,e_rh	2.146 W
P_yarm	385159 W	T0 = 1417899757
P_xarm	385159	T0 = 1417899757
Gx	0.8149	T0 = 1417899757
Gy	0.8198	TMS * pi G    =   cos2 (   ----------------   )                       FSR
Ai_y	-16 uD/W
Ai_x	-26 uD/W

---

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

Morning Purge Air Check

Dry air skid checks, water pump, Kobelco, all nominal.  Noticed extra noise coming from the left dryer tower (rattling), maybe a one of the left side one-way valves is showing its age.

Dew point measurement at HAM1 -45.7 °C.

.

Wed CP1 Fill

Wed May 07 10:12:33 2025 INFO: Fill completed in 12min 29secs

Gerardo confirmed a good fill curbside.

Geist environmental monitors installed in out-buildings

WP12510 FRS34002

I have installed the four Geist Watchdog 1250 rack mount units in the CDS computer racks at MX, MY, EX and EY.

At the end stations these units are mounted close to the top of the CDS front-end computer racks, forward facing (see attached photo of EY). The end station computer racks are located in the first room you enter from outside.

At the mid stations these units are mounted in the VEA computer rack, located roughly in the center of the VEA. All the internal roll-up doors are open, essentially making the whole building one very large room.

EPICS IOCs were created to read out these units, and their channels were added to the DAQ yesterday.

I have added an environment section to the CDS overview (see attachment) which provides visual alerts if any out-building sensor is out-of-bounds.

The LEDs show light_level (L), sound_level (S), temperature (T) and humidity (H).

In the example shown, the EX lights are on.

Ops Day Shift Start

TITLE: 05/07 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: LIGHT_MAINTENANCE_WINDY
    Wind: 1mph Gusts, 0mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.14 μm/s
QUICK SUMMARY: More alignment in HAM1 and wind fence work at EX lined up for today.

• Currently ~1.9W into IMC
• HAMs 2, 4, and 5 ISOLATED w/ HEPI ISO gains to 0
• All BSCs FULLY_ISOLATED
• DR and LAB2 dust monitors report NaN entries

Diode room dust monitor issues today

The DM first starting having issues at ~11am 2 weeks ago on April 22nd (Tues) for seemingly no reason, there wasn't any work or alogs that day that would made us suspicious of causing this.

Following my alog comments on alog84282, Dave showed me where the physical comtrol box is in the CER, restarting it brought the connection back but I then found that the dust monitor had no flow :(. This DM hasn't been used since we got it calibrated in April of 2024, so I swapped it for the last pumpless spare we had which has good flow but now it's not connecting again. I've tried powercycling the DM itself, the ioc, and the comtrol box then the ioc which is what got the other DM to reconnect, and it still getting "No reply from device within 1000 ms" for all its PVs. The DM it self is working and reading counts properly.

Doing a telnet network status (comand "ss -e") on h0epics for the diode room port yielded:

timer:(keepalive,38min,0) uid:1001 ino:20939307 sk:ffff8800b67bd500
ESTAB       0      0                                                                                        10.105.0.80:37347                                                                                    10.105.0.100:8000 

 

Relationship between violin mode height and narrow spectral artifact contamination, revisited

Summary

Q: What is the relationship between the strength of violin mode ring-ups and the number of narrow spectral artifacts around the violin modes? Is there a clear cut-off at which the contamination begins?

A: The answer depends on the time period analyzed. There was an unusual time period spanning from mid-June 2023 through (very approximately) August 2023. During this time period, the number lines during ring-ups was much greater than in the rest of O4, and the appearance of the contamination may have begun at lower violin mode amplitudes.

What to keep in mind when looking at the plots.

1. These plots use the Fscan line count in a 200-Hz band around each violin mode region, which is a pretty rough metric, and not good for picking up small variations in the line count. It's the best we've got at the moment, and it can show big-picture changes. But on some days, contamination is present, but only in the form of ~10 narrow lines symmetrically arranged around a high violin mode peak. (Example in the last figure, fig 7) This small jump in the line count may not show up above the usual fluctuations. However, in aggregate (over all of O4) this phenomenon does become an issue for CW data quality. These "slight contamination" cases are also particularly important for answering the question "at what violin mode amplitude does the contamination just start to emerge?" In short, we shouldn't put too much faith in this method for locating a cut-off problematic violin mode height.

2. The violin modes may not be the only factor in play, so we shouldn't necessarily expect a very clear trend. For example, consider alog 79825 . This alog showed that at least some of the contamination lines are violin mode + calibration line intermodulations. Some of them (the weaker ones) disappeared below the rest of the noise when the violin mode amplitude decreased. Others (the stronger ones) remained visible at reduced amplitude. Both clusters vanished when the temporary calibration lines were off. If we asked the question "How high do the violin modes need to be...?" using just these two clusters, we'd get different apparent answers depending on (a) which cluster we chose to track (weak or strong), and (b) which time period we selected (calibration lines on or off). This is because at least some of the contamination is dependent on the presence & strength of a second line, not a violin mode.

Looking at the data

First, let's take a look at a simple scatter plot of the violin mode height vs the number of lines identified. This is figure 1. It's essentially an updated version of the scatter plots in alog 71501. It looks like there's a change around 1e-39 on the horizontal axis (which corresponds to peak violin mode height).

However, when we add color-coding by date (figure 2), new features can be seen. There's a shift at the left side of the plot, and an unusual group of high-line-count points in early O4.

The shift at the left side of the plot is likely due to an unrelated data quality issue: combs in the band of interest. In particular, the 9.5 Hz comb, which was identified and removed mid O4, contributes to the line count. Once we subtract out the number of lines which were identified as being part of a comb, this shift disappears (figure 3).

With the distracting factor of comb counts removed, we still need to understand the high-line-count time period. This is more interesting. I've broken the data down into three epochs: start of O4 - June 21, 2023 (figure 4); June 21, 2023 - Sept 1 2023 (figure 5); and Sept 1 2023 - present (figure 6). As shown in the plots, the middle epoch seems notably different from the others.

These dates are highly approximate. The violin mode ring-ups are intermittent, so it's not possible to pinpoint the changes sharply. The Sept 1 date is just the month boundary that seemed to best differentiate between the unusual time period and the rest of O4. The June 21 date is somewhat less arbitrary; it's the date on which the input power was brought back to 60W (alog 70648), which seems a bit suspicious. Note that, with this data set, I can't actually differentiate between a change on June 21 and a change (say) on June 15th, so please don't be misled by the specificity of the selected boundary.