J. Kissel, S. Dwyer, others

Just so others can see what we're seeing, here's the glitch at 2025-05-28 15:36 UTC that drove us to swap the F1/F2/F3/LF Triple Top coil driver on the H1SUSBS. 

Everything's wrapped in loops, so it's difficult to point fingers at any one component.
ISI is in FULLY_ISOLATED_NO_ST2_BOOST per normal for MICH lock acquisition
SUS has 
    - M1 OSEM PD to M1 OSEM Coil damping loops ON (L, T, V, R, P, Y)
    - M3 Oplev QPD to M2 OSEM Coil damping loops ON (P and Y)
The IFO was attempting to lock PRX.
This is unexpected, but apparently there's also some slow ISC loop that is really causing the majority of the alignment excursion.

Will keep investigating other times to see if this is a consistent issue. 
We've looked at a few other times where we suspect optical lever glitching, but the same ISC loops were not on.
Difficult to trend the configuration of the ISC loops at the moment, 'cause folks are trying lots of different configurations to get DRMI relocked.

We'll post if we find an answer.

We swapped the coil driver because the "glitch" showed up "most" in the F1 sensor, and we feared it was something like we've seen in the past -- SR3 top mass coil driver failures that took us a long time to find (see LHO:62038 and LHO:62123).

J. Freed

The reason we picked the ZFL-500HLN amp for SPI's Double Mixer was that it was an amp that met requirements from minicircuts

-frequency range contains 80MHz (our operating frequency)

-Operates at voltage supplied by Low Noise Power(15V, 17V, 24V etc.)

-Has a P1dB well above our output power of 10dBm (to remove non-linearity)

-No heat sinks (to fit in a 1U chassis.) (This requirement actually doesnt matter, the ones discussed here are still the best even compaired to amps with heat sinks)

-sma connections

-Low noise

-Low gain (we only need ~8dB of amplification)

The ZFL-500HLN was chosen because it fit all those requirements, with the cavieat of having to attuniate before amplification (adding noise). Though if I am correct and the Low noise power board 5V Vcc port is capable of supporting a 63mA load, another option would be the ZX60-P105LN+ instead due to the lower gain and lower noise. This would remove the need for an attinuator before amplification but its low input return loss means alot of power is reflected back towards our mixers (Also causeing noise). So it becomes a pick your poison of adding noise by attinuating before amplification vs by reflections back into our mixers. In practice, I believe both would operate about the same. Will add a comment if something changes

Double-MixerAmpComparison.png shows a quick comparison of the 2 amps

J. Kissel

As we begin to investigate transient issues with the Beam Splitter where its sensors are reporting intermittent glitching that is spoiling DRMI locking, the optical lever damping loops are always an open question for me. 

Here's the impulse response of the filters, shown both as a normal time-series, which shows that most of the action happens within the first 0.2 seconds. I also show a semilogx plot of the time series to show the early magnitude of the response.

Finally, I attach a screenshot of which filters are on.

Sheila, Camilla

As we've had trouble catching PRMI, and there is some signs of the BS oplev laser glitching, see attached. We turned up the laser current so that the Oplev NSUM counts increased from 16,000 to 20,000. BS Oplev laser is in the cooler behind the HWS table / TCSX rack.

TITLE: 05/28 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 5mph Gusts, 0mph 3min avg
    Primary useism: 0.13 μm/s
    Secondary useism: 0.10 μm/s
QUICK SUMMARY:

H1 currently in ready state.
Seimic system back to calm after a few earthquake.
I got ALS Locked after touching up Y arm.
I'm going to Try to get DRMI locked for the Comissioners, before they arrive. Im going to try once with out a Full Initial Alignment first and then run an initial alignment since the alog 84610 has it in bold, perhaps I should try it.
 

TITLE: 05/28 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: More progress this evening with H1 locking! We've been able to reach 'RESONANCE' and set the green references there, but DRMI/PRMI locking has continued to be a struggle where flashes will look good, but it will not lock for a long time for some reason. See other logs, mainly alog84610, for details.

As Elenna mentions in her log, first thing in the morning a FULL initial alignment should be run! [Tagging OpsInfo]

LOG:

Ryan S., Sheila, Elenna

First thing Wednesday morning: run full initial alignment with green cameras

Ryan and I were able to lock the IFO on DRMI after many hours struggling down rabbit holes. In short: we were able to finally lock DRMI after reverting the ITMX and ITMY alignment to the alignment on Friday, and running manual initial alignment.

Sheila came online while we were in DRMI checking various things, and together we made it to CARM on Resonance. The alignment was very good (mostly hand tuned except for MICH ASC and DHARD). Sheila and I did our usual check of the PRG following alog 62110 and confirmed that everything looks great.

From there, Ryan and I ran the green camera offset scripts, watched them converge, and set the camera values. These are all SDFed- Ryan will add screenshots. To reiterate: run full initial alignment!

Sheila will add comments about checking and fixing the REFL phases.

While Sheila was adjusting the REFL phases so we could go to CARM on analog, I tried setting up the POP X centering using PM1 (so we could do DRMI on POP). I confirmed that moving PM1 moves the beam on POPX in reasonable ways. I had to flip the DC centering sign to positive when I engaged the loop, DC6, so the centering would converge. I was trying to check the UGF of the DC6 pitch loop by adding an offset to the loop, and accidentally added a massive offset, which tripped a lockloss since the beam went crazy on POPX and therefore LSC POP and that's a lockloss trigger diode.

I also had to turn on the PM1 signal output from the ASC model, which I then SDFed. After lockloss, the PM1 locking output doesn't get cleared, so Sheila will add that to the list of suspensions to clear after lockloss.

Georgia, Jenne, Elenna

All new offsets SDFed. I lazily accepted all the offsets without screenshots (ASC, ASCIMC, LSC, ALSEX, ALSEY, ISCEX, ISCEY, OMC). Running the script seems to have helped with our DRMI locking problems.

M. Todd, C. Cahillane

Revisiting the dataset from the March 10th, 2025  intensity noise injections that I did, Craig and I re-did a CARM pole estimate as followed in alog 65093.

Results: we estimate the CARM pole to be 0.67 +/- 0.005 Hz.

Using the Transmitted ARM RIN channels transfer function from intensity noise, we can fit a 1/f line to the low-frequency portion to estimate the CARM pole.

The plots below show some slight variation between the different channels, but all consistently around 0.67 Hz CARM pole. I have yet to examine exactly what this means for our loss estimates.

Code:

The code used to make the below plots is found:

List of Figures:

1. All together plot pdf with all transfer functions and CARM pole fits in one document
2. ISS RIN to TRX - A RIN and CARM pole fit
3. ISS RIN to TRX - B RIN and CARM pole fit
4. ISS RIN to TRY - A RIN and CARM pole fit
5. ISS RIN to TRY - B RIN and CARM pole fit

Jennie W, Sheila, Jenne D, Tony S,

Summary: PRCL loop seems to be behaving ok. Not sure why we can't lock DRMI.

We were having trouble staying locked in DRMI today so we did some open loop transfer function (OLTF) measurements of the PRCL, PRX and PRY length loops as a cross-check.

Below I include photos of the PRCL OLTF measurement where you can see there is no coherence below 20 Hz and there is a small bump in the measurement between 20 and 30 Hz.

This seemed strange so we measured PRX (state in ALIGN_IFO guardian) and PRY

Steps to lock PRY:

• I misaligned ITMX and aligned ITMY suspensions.
• Jenne D rand the PREP_FOR_PRX state in ALIG_IFO guardian
• then ran altered steps from AQUIRE_PRX state from the guardian terminal to lock us in PRY.

From the OLTF for PRX (brown trace) and PRY (red trace) we can't see any strange behaviour between 20 and 30 Hz in either state.

Finally I compared the PRCL OLTF to a measurement Ryan did a year ago, and from this (red trace) it looks as if that gain bump between 20 and 30 Hz and the rest of the TF shaping is nominal.

For completeness I include the measurement I did of MICH while PRMI was locked.

Sheila, Jennie W, Elenna,

We need to set up two DC centering loops for the PM1 suspension using the new in-vac POP_X PD.

Sheila copied over the H1:ASC-DC1_P and Y filters to the H1:ASC-DC6_P and Y filter banks after checking the shaping of these loops, and that the input and output matrices for both DOFs direct POP X  DC input -> DC6 -> PM1. We loaded the coefficients in H1:ASC model.

Elenna put in gains to match those used by DC1 and turned on the corresponding filters in the DC 6 filter banks. The inputs are off for now and we can test these later.

The chiller systems at the mid stations were started this morning for the season. 

Oli, Edgard, Jeff, Brian

This post is meant to give a clearer explanation of the work in [LHO:84296] and its many comments. We are trying to find a new set of gains for the M1_OSEMINF filter banks for SR3 to calibrate the OSEMs to be in agreement with the HAM5 GS13s.

To do so, we drive the HAM5 ISI in { X , Y , Z } and record the response of the relevant OSEMs between 5 to 15 Hz.  At these frequencies, the M1 stage of the suspension should start to become inertial, and the M1_DAMP / SUSPOINT response of each individual OSEM should asymptote to -1, because the OSEMs would be measuring their support point on the cage [barring internal dynamics of the cage itself].

To increase the accuracy of the calibration, we use the MATLAB model of the HLTS and use the full extent of the 5-15 Hz data instead of only the asymptotic behavior.

I post here the code used to generate these results. The code requires the new Common/MatlabTools/ExportedModels folder from the SusSVN [LHO:84458]. The detailed results of the calibrations mentioned is shown below.

_____

• We took a series of transfer functions driving HAM5_ISO_{ X , Y , Z } to measure SR3_M1_DAMP_{L,T,V,R,P,Y}. The templates for this measurement are saved in the sus SVN under [HLTS/SR3/H1/Common/Data/]
  • We can see a lot of cross-coupling in some of these transfer functions. For example, the first attachment shows SUSPOINT V to M1 R cross-coupling that ends up being consistent with sensor miscalibration. This miscalibration is also seen in the large V-to-R and R-to-V couplings in the M1 to M1 transfer functions that Oli took in [LHO:83939].
• From the measurements, we reconstruct the following transfer functions:
  • SUSPOINT V to SR3_M1 T1, T2, and T3. Which are the OSEMs related to the V, R, and P degrees of freedom of SR3.
  • SUSPOINT L to SR3_M1 LF, and RT. Related to the L and Y degrees of freedom.
  • SUSPOINT T to SR3_M1 SD. Related to the T degree of freedom
• These transfer functions are shown in the second attachment. Two interesting things to note:
  • None of them asymptote to -1. In amplitude, they hover around 0.75 or so.
  • The Vertical sensors are backwards. This is not important for what we're doing, we will calibrate by using the absolute value.
• We can get the scaling factors needed to make them asymptote to one by fitting the individual OSEM transfer functions to the model.  We fit by using linear regression between 5 and 15 Hz. The scaling factors calculated from the figures in the second attachment are:
  • T1 needs to be multiplied by:   2.4539
  • T2 needs to be multiplied by:   1.4819
  • T3 needs to be multiplied by:   1.4125
  • LF needs to be multiplied by:   1.3206
  • RT needs to be multiplied by:   1.3705
  • SD needs to be multiplied by:   1.3806
• Therefore, after we multiply the OSEMINF gains that were in place at the time of measurement by these scaling factors, the new OSEMINF gains should be:   
  • T1: 3.627
  • T2: 1.396
  • T3: 1.345
  • LF: 1.719
  • RT: 1.490
  • SD:1.781
• The T1 gain is egregiously high, which makes all of us a bit nervous. Oli has been in the process of checking if these numbers actually make sense. These results will be posted in another log... This one is already too long.