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

Dew point measurement at HAM1 , approx. -42C

The turbo on the YBM tripped as a result of the power glitch reported last night see alog 84217, leading to a slight pressure rise in the corner.

I closed the main gate valve at that turbo and restarted the scroll pump/backing turbo and main turbo. Once the turbo reached full speed and the intake pressure was lower than the main volume pressure I verified trip setpoints and re-opened the gate valve..

This was the only turbo station that tripped. Output tube/XBM & HAM6 turbos were all nominal.

Another site power glitch, caught by GC OSB UPS but not CDS MSR UPS. Seen by CS MAINSMON.

My house lights flickered around this time.

UPS email:

Date : 04/30/2025
Time : 21:39:31
Code : 0x0109

Warning - UPS: On battery power in response to an input power problem.

Jonathan, Dave:

I have added the new third framewriter (FW2) to DAQSTAT.

H1:DAQ-FW2_STATUS is now viewable in the DAQ section of the CDS Overview (see attached).

TITLE: 05/01 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: MAINTENANCE
    Wind: 4mph Gusts, 3mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.12 μm/s
QUICK SUMMARY:

Vent work today includes:

• EY wind fence
• HAM1 beam profiling
• PM1 installation
• HEPI upgrade software
• HAM4/5 cable tray work
• Ground checks of LSC/ASC diode boxes now fully cabled

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.

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.

Calibration is currently regenerating the O4b uncertainty budgets.

Due to a missed change to the ETMX UIM suspension filters, which was found in LHO alog 82804, and then fixed only on Feb 27, 2025 (see LHO alog 83088), we need to add a correction TF to be included in the uncertainty budgets.

I attach a graph of that correction TF (corrected model / original model) and the text file needed for that correction.

We will be using correction TF in all our uncertainty budgets for O4b, and up to Feb 27, 2025 around 20:00 UTC, or GPS 1424721618 for O4c.

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