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

Dew point measurement at HAM1 , approx. -41C

TITLE: 04/30 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, 2mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.12 μm/s
QUICK SUMMARY:

The planned work today includes:

• Mostly Laser Haz with PSL_IN @200mw for initial beam path alignment work
• Beam position measurement
• HAM1 - Beam Path alignments
• Install PM1, cable up, start troubleshooting, ground checks
• HEPI upgrade software part start
• VAC - HAM1 Top flange Gauge work table side - GM?
• EY wind fence work

PCal team took PS4 to EY again today for the first every April measurement of End Y! Previous Aprils'  measurements have apparently all been EndX.

Following T1500062V-18, Nothing really out of the ordinary except I put RX here instead of bolting to the side of the breadboard like I normally do, to see if that has any effect on the load balancing of the RX optical bread board or any impact to the overall measurement during the time when WS was in the RX side.
Beam spot

python3 generate_measurement_data.py --
WS "PS4" --date "2025-03-24"
Reading in config file from python file in scripts
../../../Common/O4PSparams.yaml
PS4 rho, kappa, u_rel on 2025-03-24 corrected to ES temperature 299.4 K :
-4.701550919294612 -0.0002694340454223 4.0632996079052654e-05
Copying the scripts into tD directory...
Connected to nds.ligo-wa.caltech.edu
martel run
reading data at start_time:  1429997850
reading data at start_time:  1429998230
reading data at start_time:  1429998550
reading data at start_time:  1429998990
reading data at start_time:  1429999330
reading data at start_time:  1429999640
reading data at start_time:  1430000100
reading data at start_time:  1430000600
reading data at start_time:  1430000920
Ratios: -0.5349326615859125 -0.5432025342228874
writing nds2 data to files
finishing writing
Background Values:
bg1 =        17.394679; Background of TX when WS is at TX
bg2 =        4.438216; Background of WS when WS is at TX
bg3 =        17.479506; Background of TX when WS is at RX
bg4 =        4.610581; Background of WS when WS is at RX
bg5 =        17.487987; Background of TX
bg6 =        -0.718008; Background of RX

The uncertainty reported below are Relative Standard Deviation in percent

Intermediate Ratios
RatioWS_TX_it      = -0.534933;
RatioWS_TX_ot      = -0.543203;
RatioWS_TX_ir      = -0.527567;
RatioWS_TX_or      = -0.535369;
RatioWS_TX_it_unc  = 0.055737;
RatioWS_TX_ot_unc  = 0.055881;
RatioWS_TX_ir_unc  = 0.056510;
RatioWS_TX_or_unc  = 0.055480;
Optical Efficiency
OE_Inner_beam                      = 0.985953;
OE_Outer_beam                      = 0.985408;
Weighted_Optical_Efficiency        = 0.985681;

OE_Inner_beam_unc                  = 0.042868;
OE_Outer_beam_unc                  = 0.044311;
Weighted_Optical_Efficiency_unc    = 0.061653;

Martel Voltage fit:
Gradient      = 1637.860873;
Intercept     = 0.156301;

 Power Imbalance = 0.984776;

Endstation Power sensors to WS ratios::
Ratio_WS_TX                        = -0.927527;
Ratio_WS_RX                        = -1.383600;

Ratio_WS_TX_unc                    = 0.045873;
Ratio_WS_RX_unc                    = 0.042755;

=============================================================
============= Values for Force Coefficients =================
=============================================================

Key Pcal Values :
GS           =      -5.135100; Gold Standard Value in (V/W)             
WS           =      -4.701551; Working Standard Value             

costheta     =      0.988362; Angle of incidence
c            =      299792458.000000; Speed of Light
             
End Station Values :
TXWS         =        -0.927527; Tx to WS Rel responsivity (V/V)
sigma_TXWS   =        0.000425; Uncertainity of Tx to WS Rel responsivity (V/V)
RXWS         =        -1.383600; Rx to WS Rel responsivity (V/V)
sigma_RXWS   =        0.000592; Uncertainity of Rx to WS Rel responsivity (V/V)

e            =        0.985681; Optical Efficiency
sigma_e      =        0.000608; Uncertainity in Optical Efficiency

Martel Voltage fit :
Martel_gradient         =        1637.860873; Martel to output channel (C/V)
Martel_intercept   =        0.156301; Intercept of fit of     Martel to output (C/V)

Power Loss Apportion :
beta          =        0.998844; Ratio between input and output (Beta)  
E_T          =        0.992240; TX Optical efficiency
sigma_E_T          =        0.000306; Uncertainity in TX Optical efficiency
E_R          =        0.993389; RX Optical Efficiency
sigma_E_R          =        0.000306; Uncertainity in RX Optical efficiency

Force Coefficients :
FC_TxPD          =        9.160033e-13; TxPD Force Coefficient
FC_RxPD          =        6.229843e-13; RxPD Force Coefficient
sigma_FC_TxPD          =        5.093831e-16; TxPD Force Coefficient
sigma_FC_RxPD          =        3.305931e-16; RxPD Force Coefficient
data written to ../../measurements/LHO_EndY/tD20250429/

This adventure was brought to you by, Francisco L & Tony S.
 

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.

Summary: This work aims to understand the shape of the DARM sensing function as affected by mode mismatches and input power. It seems that the mismatches affect the detuning of the SRCL DOF, that is it affects the locking point, but not the shape of the DARM sensing funciton. However, the input power, which causes radiation pressure, has a bigger effect on it. If I do not include QUADsuspension option, then I get a flat response function regardless of the mismatch or the input power. 

For the past week I have been studying the effect of SCRL DOF detuning (or sometimes I refer to it as offset) on the DARM readout using FINESSE.
In FINESSE, that is done by changing SRCL.DC, and looking at the transfer function from DARM.AC.i to AS.DC.o

The reason being to understand the measurement of the sensing function taken and show here. 
My system include up to maxtem=4, QUADsuspensions,     InitialLock > DARM_RF_to_DC.

Before we start doing that, let’s understand the error signal of SRCL DOF. This is read at POP45_I channel. The ideal tuning of this loop is SRCL.DC=90, that is the case where the carrier beam is anti-resonant in the SRC, while the sidebands are.  At that detuning, the error signal is 0. However, since we do not have a perfect model, there is some mode mismatch between SRC and the arm cavities. This will inject some higher order modes carrier and sidebands into the SRC and that changes the locking point. Using the default cold state LHO model, the detuning at which the error signal is 0 is SRCL.DC=-90.4643
This is shown in the plot below (Error_signals_vs_detuning.pdf)

Let’s look at this offset as the mode mismatch changes. I adjust ITMlenses focal lengths and measure the mismatch between SRX and XARM cavities, and SRY and YARM cavities. I also have an amplitude detector to measure the power in the HG20/02 modes at the AS port, which might be partially resonant in the SRC due to its low finesse. (Detuning_vs_SRC_ARMS_mismatch.pdf) 

On the x-axis is the SRY to YARM mismatch percentage, and on the y-axis is the SRX to XARM mismatch percentage. I’m not sure why there is such a big difference of mismatches in the default cold state model, but the qualitative behavior is what we need here. 
The colors represent SRCL.DC offset while the numbers on each cell represent the power in the 2nd high order mode in W. 
We notice that as the SRY to YARM mismatch gets closer in magnitude to SRX to XARM mismatch the offset decreases and goes towards 90, and the power in the 2nd HOM also gets smaller, which suggests that the presence of these modes affects the offset, as we would expect(see also This old technical note)
I believe the reason that the HOM gets smaller as the mismatches get closer together can be imagined similar to what the Michelson interferometer does to the fundamental mode for HG20/02 modes that are at the same phase, they cancel each other out at the AS port. 

Finally, let us look at the DARM sensing function, which is our goal of this investigation. 
We would expect the sensing function to be flat starting around ~7Hz and keep like that until it starts rolling off at ~ 200 Hz. 
Now, here is the surprise, I plotted the response function in the default case where there is mismatch between SRC and the arm cavities, and then I changed ITMXlens focal lengths to get almost perfect mode matching, and it turns out that they are not that different, as seen below (Comparison_with_different_MM.pdf)

What seems to be affecting the response function is not the mode matching (even though it affects the locking point), but the input power value. If I reduce the input power to 1W instead of 60W that is used in the comparison plot, I get the following response function (yes, I checked the error signal zero point is still at 90.464 (1W_DARM_readout_vs_detuning.pdf)

And so, from this investigation, it seems that the input power affects the response function more than the mode matching, while the mode matching affects the locking point. 

Next, I reset the model and I started changing the reflectivity of the SRM, narrowing the linewidth and increasing the finesse of the cavity. As the finesse increases, the detuning goes towards 90 degrees. This could be from reducing the effect of the HOM on the fundamental mode in SRCL.  (SRM_reflectivity.pdf)

Sheila, Keita, Elenna, Camilla, Jason, TJ  WP# 12491.

With MC2 misaligned, TJ transitioned to laser hazard and opened the PSL IR light pipe.

Keita checked that the MC REFL path on IOT2L was aligned-ish. We had a beam on the LSC REFL DC and on WFS A. Not much on WFS B. Sheila moved the input PSL PZT to improve pointing onto WFS A.

We were getting flashes on MC2 trans so went to the control room where Sheila zero’ed H1:IMC-WFS gain (was 0.04) and continued to move PSL PZT to maximize MC2 trans flashes (could also see flashes on IM4 trans).

Once these flashes were maximized, Sheila tried to lock with the guardian (which automatically sets gains and thresholds based on input power). Locked but didn’t look great. Sheila and Keita edited the IMC_power_adjust_fuc() of ISC_libary.py so nothing is done when the PSL input power < 1W. IMC then locked great.

During the IMC locking, we had some troubleshooting here as we kept getting “PMC unlocked” notification taking IMC_LOCK to FAULT. Jason explained this could get it getting to the end of its range and while it swaps to the other side of its lock might trigger the notification, even though we could not see it on ndscope. We also had the FSS unlock and the autolocker not able to relook. Jason took PSL FSS common and fast gains to zero, let it settle then brought common and then Fast gains slowly back. This happened a once more where we also had to turn off /on the auto-locker to make it settled.

On IOT2L, everything  (camera and diode) in the IMC trans path was fine, left as is. In the IMC REFL path, the beam was not centered on the high power beam dump (maybe wasn't originally) so we moved IO_MCR_M3. We then checked we were on the plateau of the the LSC diode with IO_MCR_BS1 and checked we weren’t near the edge of the TRIG diode.  We moved the IO_MCR_BD6 beam dump so it was centered on the beam. We moved IO_MCR_BS2 and BS3 to center the beams on WFS A and B.  Sheila moved IO_MCR_M12 up to get MC TRANS on the GiGe camera. Everything on IOT2L is now aligned. 

Checked in-vac and in-air powers are correct-ish by comparing them to 2W IMC locked/ unlocked. Sheila and Elenna locked IMC with WFS centering servos back on and offloaded the WFS. 

As Ibrahim checked yesterday 84153, the IMs are a little different but Elenna checked the beam centering on IM4 trans is close to when we were locked: P was 0.24 now 0.2, Yaw was -0.08 now -0.13. 

Keita restored SR2, SR3, BS, ITMX to a time 31 days ago when IFO was locked and could see the beam on the AS AIR camera. 

We have left the IMC offline and PSL IR light pipe closed. 

TITLE: 04/29 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: We had a few earthquakes roll through in the morning, 6.8 from south of New Zealand and a 4.8 from Puerto Rico. The LVEA is now in LAZER HAZARD.
LOG:                                                                                                                                                                                                                                                            

Some of the work today includes:

• EY wind fence work Ongoing
• HAM1 cable work ?
• Ground checks of LSC/ASC diode boxes now fully cabled Done alog84174
• HAM1 - RM finish SUS troubleshooting - get suspended with good TFs Ongoing alog84178
• VAC - HAM1 septum plate removal Done alog84175
• PCAL EndY DONE
• HAM4/5 cable trays with craning Done?
• When all SUS, SEI, PSL seem in good order, transition to Laser Haz and perform 200mW lockout power into HAMs Ongoing
• Model work, DAQ restart No Restart alog84177
• Clean room moves, BSC8 DONE
• IOT2L realignment alog84187

Continued from LHO alog 84128.

RM1 (Tip Tilt suspension)

Last week Daniel and I replaced the original TT bosem cable (with a new 25in long, D2100049 S/N 2200358) since the original cable was having issues with grounding. However, Betsy informed us that the new cable might have pin 1 missing (and should be sent back to CIT for repair). I inspected the cable in-chamber and found pin1 missing.

Hence, I replaced the 25in long D2100049 S/N 2200358 (missing pin 1) with 54in long D2100049 s/n S2100426 cable. However, the ground loop issues has now returned (shorting with the chamber itself) and it looks like the culprit is not the cable but the bosem itself (despite having kapton tape for shielding, clearly its not enough). I am still considering to slide a kapton sheet underneath RM1.

Also, I measured the Open light counts of all four bosems for RM1 and they are listed below,

RM2 (Tip Tilt suspension)

Kissel, Betsy, Rahul

Here, Jeff suspects that the bosem magnet polarity is incorrect (i.e is not as per E1400316) which was recorded in his LHO alog from 2018. To verify Jeff's claim we went back into the chamber to check the polarity of RM2 magnets. However we faced two problems over here. At first I looked into the Tip Tilt assembly drawing and then the Tip Tilt PEEK flags in Triples lab to locate the magnet inside the flag. It turns out that the magnet is buried deep inside the PEEK flag, such that my polarity tester cannot detect its presence. Hence, I took another strong magnet to check if its pulling or repelling it - which worked fine. The second problem we faced was that the PEEK flag are a very tight fit inside the TT mirror holder (in-chamber) and despite our best efforts (both Betsy and I tried unscrewing it) we couldn't remove it for checking. Hence, we were unsuccessful in measuring the magnet polarity and after some discussion we decided to move ahead and reset RM2 (digitally) to how it was before this vent. Jeff will file an FRS ticket regarding this issue.

The Open light counts for RM2 is given below,

I have accepted the SDFs for both RM1 and RM2 and three screenshots are attached below.

Today, Dave and I did the final bit of WP 12467.  We connected a monitor and keyboard and configured the networking on h1hpipumpctrlcs, which is the new hpi beckhoff controller for the corner station.  Filiberto had done the physical link to the CDS switch earlier.  We were able to share the monitor with the old control computer as the new and old systems had different video connectors, but there is a new keyboard for the new computer.  If anyone needs to work on it, we need to get a usb mouse out there as well.

Now that it is on the network Patrick can remotely access and start programming the new controller.

At this point there is nothing hooked up for it to control.

Gerardo, Camilla, WP 12491

Also fixed the LSC POP helicoil so all diodes are now cabled, details in 84174

Edgard, Oli.

Follow up to the work summarized in 84012 and 84041.

TL;DR: Oli tested the estimator on Friday and found the ISI state affects the stability of the scheme, plus a gain error in my fits from 84041. The two issues were corrected and the intended estimator drives look normal (promising, even) now. The official test will happen later, depending on HAM1 suspension work.

____

Oli tested the OSEM estimator damping on SR3 on Friday and immediately found two issues to debug:

1) [See first attachment] The ISI state for the first test that Oli ran was DAMPED. Since the estimator was created with the ISI in ISOLATED (and it is intended to be used in that state), the system went unstable. This issue is exacerbated by point 2) below. This means that we need to properly manage the interaction of the estimator with guardian and any watchdogs to ensure the estimator is never engaged if the ISI trips.

2) [See second attachment] There was a miscalibration of the fits I originally imported to the front-end. This resulted in large drives when using the estimator path. In the second figure, there are three conditions for the yaw damping of SR3:
           ( t < -6 min )          OSEM damping with gain of -0.1.
    ( -6 min<  t  < -2 min)   OSEM damping with a gain of -0.5, split between the usual damping path and the estimator path.
     ( -2 min < t < 0 min)     OSEM + Estimator damping.

The top left corner plot shows the observed motion from every path. It can be seen that M1_YAW_DAMP_EST_IN1 (the input to the estimator damping filters) is orders of magnitude larger than M1_DAMP_IN1 (the imput to the regular OSEM damping filters).

The issue was that I fit and exported the transfer functions in SI units, [m/m] for the suspoint to M1, and [m/N] for M1 to M1. I didn't export the calibration factors to convert to [um/nm] and [um/drive_cts], respectively.

____

I fixed this issue on Friday. Updated the files in /sus/trunk/HLTS/Common/FilterDesign/Estimator/  to add a calibration filter module to the two estimator paths (a factor of 0.001 for suspoint to M1, and 1.5404 for M1 to M1). The changes are current as of revision 12288 of the sus svn.

The third attachment shows the intended drives from the estimator and OSEM-only paths. They look similar enough that we believe the miscalibration issue has been resolved. For now we stand by until there is a chance to test the scheme again.

Oli, Camilla.

Following work done in 84115 to repopulate HAM1 with some optical components, today Oli and I placed the SLED in position and placed all the diodes, most (not LSC POP A ) are cabled. Photos taken from -Y side and +Y side attached.

Apart from LSC POP A, they are all cabled up according to the cables in D1000313 BOM googlesheet. LSC POP A has a heli-coil that needs replacing before we can install the RF cable so neither cable are currently installed. ASC REFL A and B are in the incorrect position to allow for beam profiling before moving the the final position. LSC REFL A and B may need to be moved slightly but we need more of the correct size dog clamps to allow that. 

I keep forgetting to reset the dust monitor alarm levels after IOC restarts so I wrote a little script to check all of the dust monitor alarms levels and reset them if needed based on E1600132. It does not reset the LVEA ones, it just notifies, as these ones alarm levels are sometimes modified.

The scripts is called check_dm_alarms_lvls.py and lives at /ligo/cds/userscripts/. I've also updated the wiki with this info.

Some changes to the RM1/RM2/PM1:

• Zeroed the alignment offsets of RM1 abd RM2.
• Changed the signs of the coil outputs for RM1 and RM2. This should account for the sign change of the OSEM voltages.
  For reasons unknown the coils between RM1 and RM2 have opposite signs.
• Went through the PM1 model and made sure all the settings and filters are identical to RM1/2.
• The ISC/LSC input on these models is a constant. This constant was 1 and it was changed to 0. (Requires a model boot to become active.)

All other things equal the local damping loops should have the correct sign now. Thic change will also require a sign change in the ASC centering servos.

Fil Marc Daniel

We noticed that the photodiode pins of the in-air cable that connects to RM1 and RM2 were flipped. This will flip cathode and anode which will only matter if there is a bias applied.

Going thru the schematics it seems that with 1:1 wiring the PD anode and cathode are flipped compared to what is shown in Sat Amp D080276. I assume somebody noticed this and flipped the corresponding pins of the in-air cable to correct for it back in 2013.  The polarity of the PD doesn't really matter, if there is no bias. We checked the RM sat amps and they have no bias.

If the Sat Amp PDs are connected as shown om D080276, the OSEM values will be negative. Indeed, the RMs had negative OSEM values as expected. However, all ZMs have positive values, since nobody bothered to flip the pins. We propose to no longer flip the PD pins for the RMs and work with positive OSEM values in the future.