Keita, Elenna, Oli, Rahul, Camilla

Summary: Majority of REFL path optics are aligned. Need to beam profile and finish LSC and ASC REFL diode placement on this path and place/check all beam dumps.

This morning, Keita opened the light pipe, locked the IMC  but couldn't see the beam as nicely as he did on AS_AIR yesterday. Since that time he had restored PR2 and PR3 to a time we were last locked. He reverted those changes as we could see the beam back at AS_AIR. Checked again IM4 trans QPD was the same as yesterday.

• The beam coming out of the spectrum port was not centered on the REFL optics that had been placed as per D1000313-v19. We checked Corey's photos to compare REFL optics position relative to periscope and the D10002313 drawing and convince ourselves the beam in correct just the drawing of it is incorrect.
• Firstly checked the incoming beam was centered on M14 and the reflected beam off this was dumped on the HiPWR beam dump which was moved to it's final position.
• Beam centered on HW1
• Beam centered on M17 and the reflected beam off this was dumped on the HiPWR beam dump
• Beam centered on M1 and headed towards M2
• Beam centered on M7, following the correct beam path off the table and dumped but a temporary dump (before we put in BDV1)
• Beam centered on M2 and headed towards center of RM1.
  • Transmitted M2 beam dumped by BD8
• Rahul got RM1 and RM2 damping loops working so they are now in DAMPED nominally (changed OPS whiteboard) Rahul set sliders to zero.
• Beam centered on RM1 and headed towards center of RM2 (we had to turn RM1 in YAW)
  • BD16 placed behind RM1 but beam can't be seen to align to.
• Placed M5 in roughly correct place
• Beam centered on RM2 and headed towards center of M5 (we had to turn RM2 in YAW)
• Beam centered on M5 and headed towards the SLED
  • There was a fair bit of iteration of M2 and M5 here to get the beam to be aligned and centered on all optics through the SLED, still needed to adjust SLED mirror to get it centered on the final mirror.
• Adjusted the SLED steering mirror (in the position +X -Y) on the SLED to center the beam on the ASC REFL B diode steering mirror.
• Adjusted ASC REFL B diode steering mirror so that picomotors had some range left.
• Beam centered on M6 and headed towards L1/M18
• Beam centered on L1
• Beam centered on M18 and headed towards LSC REFL A and LSC REFL B
  • We stopped here before fully aligning these too diodes
  • LSC REFL A is aligned by eye and 22cm from L1 (+222mm FL)
  • LSC REFL B is 20cm from L1 and will be moved to match LSC REFL A tomorrow.

Additionally M16 was placed roughly in the correct position, all optics are now on HAM1 (apart from PM1) and the class-B pans are empty and packed up.

Left IMC locked.

TITLE: 04/30 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: The vent work continues...
LOG:                                                                                                                                                                                                                                                           

RM troubleshooting alog84204

EY wind fence continues

HAM1 alignment continues

Vacuum gauge work by HAM6

Following the work from yesterday post, 2 questions came up immediately. One, how much does the sensing function change with input power? We can plot it as a function of arms circulating power instead. Second, if the detuning is the same, but at different mode mismatches, do we get the same sensing function?

We can see the answer to the first question in this plot. These sensing functions are normalized to 100 Hz value. The ratio between the highest power and the lowest power sensing functions is plotted (dashed line) as well.  

Before answering the second question, let’s look at the following scenario. 

We lock the interferometer, get SRCL.DC to be -90.4643, then we change that detuning while locking. What happens to the PDH signal and the sensing function now?

Here I plotted the error signals as I change SRCL.DC detuning by ± 0.5 deg 

And the DARM sensing at different detuning looks like this 

So, we see that the sensing function significantly changes with detuning at a constant mismatch. 

So, from here, let’s answer the 2nd question. What we will do is to change the mismatch then manually offset the detuning to be the same in both cases. 

For that I look at 2 cases. The first case is the default case where there is a mismatch between SRC and ARM cavities with SRCL.DC = -90.4643 and I plot the sensing function. Now, when I change the radii of curvature of ITMX and ITMY - I get almost a perfect mode matching - SRCL.DC becomes ~ -90.004. Again, the question is, if I add an offset to make SRCL.DC = -90.4643, would I get the same sensing function as the first case, where SRCL.DC is -90.4643 due to the mismatch.

The answer turns out to be not entirely, but also it depends on the power as well. 

So, I looked at 2 cases, the first with input power of 1W, in which both sensing functions are very similar to each other in behaviour (not magnitude). The normalized plot shows that, in addition it shows the ratio between both of them.  This is shown in here

The 2nd case is with an input power of 60W. In this case, they are not as similar to each other anymore, though not so different either. 

This is shown in here

To conclude the 2nd question: the sensing function is almost the same (depending on the power) at the same detuning regardless of the mismatch (in the low mismatch limit < 2%)

Jim, RyanC

We noticed that the oplev damping values seemed pretty large, so we turned off the output for the OLDAMP. The noise increase started the morning of the 1st which makes sense as it's when the vent started.

WP 12505.

Patrick, Gerardo

I tried various restarts of the Beckhoff PLC on h0vaclx, but none of them changed the error on the PT110 gauge. I did notice an additional diagnosis of the error, which is that the status of the EtherCAT ports is abnormal, which I think is an indication that something is not right with the connection of the gauge to the h0vaclx EtherCAT network. Gerardo went out to reseat the cable and look for anything odd about it.

I went through and checked the relay trip point levels for each of the gauges on h0vaclx. I found PT110, PT180 and PT170 set to 1E-5 and changed them to 5E-5. PT132 was already at 5E-5. The other gauges do not have the trip points enabled.

PT110 1E-5 -> 5E-5
PT140 not enabled
PT180 1E-5 -> 5E-5
PT170 1E-5 -> 5E-5
PT132 5E-5
PT193 not enabled
PT192 not enabled
PT191 not enabled

After discussing with Jeff this morning, I have flipped the sign of the Coil Output filters Gain to get the damping loops going on both RM1 and RM2. These changes have been accepted in the SDF. Jeff had set it to nominal value (i.e how it was pre-vent), however this makes the suspension very angry with the WD tripping immediately. 

RM1 Coil Output Filter Gain:-
H1:SUS-RM1_M1_COILOUTF_UL_GAIN -1
H1:SUS-RM1_M1_COILOUTF_LL_GAIN 1
H1:SUS-RM1_M1_COILOUTF_UR_GAIN 1
H1:SUS-RM1_M1_COILOUTF_LR_GAIN -1

RM2 Coil Output Filter Gain:-

H1:SUS-RM2_M1_COILOUTF_UL_GAIN 1
H1:SUS-RM2_M1_COILOUTF_LL_GAIN -1
H1:SUS-RM2_M1_COILOUTF_UR_GAIN -1
H1:SUS-RM2_M1_COILOUTF_LR_GAIN 1

This sign change is done to compensate for the sign change of the osem voltages (now inmons are +ve counts, pre-vent it was -ve counts), along with wrong polarity of the magnets (which has always been there in RM2).

Both RM1 and RM2 are damping fine now.

Gerardo alerted me to the fact that PT110 is indicating an error on the H0:VAC-LX_Y0_PT110_ERROR channel. I logged in to h0vaclx and traced this to an unexpected value for the info data state readout. This should be 8 but is reading 15368. I don't know why or what 15368 means. He indicated that this appeared after they swapped in this gauge for another, so I suspect that this is the issue somehow.

J. Freed

Last week, this week, and the next week, the goal is to finalize the double mixer design, drawings and chassis. M. Pirello. has begun the drawings while I finalize the design, and we will work on the layout as well as the front plate.

Currently 83439 shows that phase noise is good except for harmonics every 4096Hz away from carrier. While any frequency more than 100Hz around the carrier should not affect SPI some of them do have an effect (namely the 8192Hz harmonic), 81593 also shows an ocsiloscope reading of the output which shows how messy the signal looks. This as such this week the focus is on reducing those harmonics.

The Q2 transistor on the Low Noise Power Board failed last week, was replaced, then it popped and replaced again. The problem was diagnosed to be the power pins on the ZFL-500HLNB+ amp. The pins stick out and touched the metal casing of another minicircuit part causing a short on the +15V supply from the low noise power board. A temporary solution of electrical tape was use to isolate the pins while a more perminate isolation for the pins will be there when it is finalized

AGBW.jpg Shows that the Agilent 4396B in spectrum analyzer mode gives less information with a smaller resolution bandwidth. The higher resolution bandwidth shows more harmonics with greater power on said harmonics. I do not know why this is, which is why I will be looking at phase noise when trying to improve harmonics.

The Agilent 4396B in network analyzer mode was used to take transfer functions of the double mixer phase delayer, IMG_1472.jpg shows the set up. The source power was 13dBm, the central frequency was 80MHz. The Span and Resolution Bandwidth were both 40kHz but changeing these values did not change much as the amplitude and phase was relativly flat around 80 MHz. A 10dB attinuator was added to the output to remove the overload message on port B that appered around 7dBm input power when I was incresing power to 13dBm.This is ok as I could calibrate the machine by replacing the phase delayer with a addaptor that let the signal go straight through. This calibration became my (0dBm 0deg) reference.  I took measuments of one port of the phase delayer at a time while terminating the other. 

This is slightly off from what was hoped for with (0dBm -90deg) difference. SPI has some 0.5dB attinuators as well as 1dB attinuators. Due to the attinuators not being their listed value at 80 MHz, Two 0.5dB attinuators on port 2 and one 1dB attinuator on port 1 seems to nearly correct the power differnece.

Continuing from here is characterizing the mixers, the summer, and RF couplers to gain inisight on reducing the harmonics.

FAMIS tasks 31304 and 31319, WP 12487

Procedure checklist for both stations completed.  No issues were identified at this time.

MX: Scroll pump hours: 226.8

       Turbo pump hours: 138

       Crash bearings: 100%

EX: Scroll pump hours: 7154.3

       Turbo pump hours: 1106

       Crash bearings: 100%

M. Todd, C. Compton, S. Dwyer, A. Brooks

As a continuation of the last alog, this is discussing how we can estimate thermal actuator contributions to the surface curvature to the test masses.

Summary:

The dataset used to estimate the ring-heater to surface curvature gain factor contained several ring heater settings and the corresponding HOM spacings at various "positions" in the span of time when that ring-heater power was used. For example, if the ring-heater power was changed and kept the same for 3 months, the HOM spacing data was examined at a random (long-lock time) portion of this 3-month period. This time, I tried to be a bit more systematic, such that we have a dataset with HOM spacing data at the beginning and end of each ring-heater power setting period. This can give us an idea if there are any drifts over time in the HOM spacing or coupling factors of the ring-heater power to surface curvature.

Each HOM spacing data-point is taken from a OMC spectrogram during a lock, and the errorbars associated with each are the spread of that HOM spacing peak.

Results:

The estimated ring-heater power to surface curvature gain is .7563 uD/W, which is very similar to the initial estimates done by Aiden; however, this is not the same value as the current one in TCS-SIM, indicating some adjustments may need to be made.

The blue dataset in the plot is data taken at the beginning of a ring-heater power setting period, while the yellow dataset is taken towards the end of the corresponding period. The estimated ring-heater power to surface curvature gain is the same for both datasets, however there is a relatively consistent downward drift over time by a few Hz in the HOM spacing. I'm not sure of the reason for this but it could be due difference in arm powers at each time.

Additionally, we expect the HOM spacing due to self-heating on top of the cold state to be around 5340 Hz, however TCS-SIM projects it to be around 5620 Hz.

Thus we estimate the change in HOM spacing due to self-heating alone to be around 175 Hz, where TCS-SIM projects it to be around 450 Hz.  This indicates the gain factor mapping absorbed power to surface curvature change may be to high, or our estimate of the absorbed power is too high. The latter can be estimated from the Hartmann wavefront sensors.

I took a look at the YAW angle for the HAM HEPIs associated with PR2 (incorrect by me) (HAM2), SR2 (HAM4), and SR3 (HAM5) based on this previous alog83705. I believe the IPS channel units are in nrad, so the largest yaw angle I see is on HAM2 with 1800 nrad or 1.80 urad, HAM2 and 4 are different by ~ 1.10 urad.

Wed Apr 30 10:11:57 2025 INFO: Fill completed in 11min 53secs

Gerardo confirmed a good fill curbside.

TJ was unable to run the 'guardutil archive-clone ...' command due to permission issues.  We looked at it, and the relevant error message was:

fatal: failed to copy file to 'IMC_LOCK/.git/objects/2f/826f205c25a6189503d831106e2dd97d7a39dc': Permission denied'

Tracing through paths, this was in /guardian/archive/IMC_LOCK/.git/....

The permissions + ownership of that file where 0600 (rw for the user), everything else was 0444 (r only for everyone) and owned by guardian:controls.  Changing the permissions to 0444 fixed things.

We did a search from the guardian machine for other files with that problem and found 24 files under /srv/guardian/archive, so we reset the permissions to clear up future problems.

Find command for searching: find . -type f -perm 600
Command for updating: find . -type f -perm 600 | xargs chmod 0444

I suspect this is a umask issue that someone had a umask of 077 set when they did an archive request.

Late entry

4-16 (Wednesday) activities:
- The previously received, poorly packaged Inficon gauge has been tested, and found functional. These tests continue, and also the HAM1 vacuum interlock gauge will be installed soon
- The BSC8 Annulus Ion Pump - after some aux cart pumping - is now able to hold the annulus pressure, at the mid- E-6 Torr region
- The rough pumpdown of the corner has started at 16:20, at the OMC turbo station, with a pair of ISP-1000 mobile pumping carts. In 4 hours, ~185 Torr was achieved, which means 1930 l/s effective pumping speed, which well corresponds with the 2000 l/s theoretical speed of the pumps
- The rough pumping still needs to be terminated in the end of the days, and so it was at 20:20
- All the turbo stations have been prepared for the HV pumping at the corner