• Watching the CRS laser since it's been installed, we've noticed some mode hopping occurring where there are these dramatic jumps between wavelengths (picture 1) or small just happening very frequently (picture 2)
  • This morning we added some thermal paste and some scrap metal on the CRS laser to try and help with the thermal regulation. 
• I looked back at the time series from when the NRS laser was plugged in and while there is still some mode hopping occurring, it doesn't have the same big hops, rather smaller ones which occur much less frequently (picture 3).
• While power cycling the TEC, we found that the mode hopping in the CRS laser reduces if the TEC is set to 10.896kΩ-10.899kΩ (rather than the recommended  10.72kΩ).  If the value is between 10.72kΩ and 10.896kΩ or above 10.899kΩ, the mode hopping worsens. In this range the mode hopping looks more like the NRS laser mode hopping (picture 4) with the occasional big jumps, but much less frequently than with other TEC settings.
  • Using 10.896kΩ the laser temperature is set to 24.42^o C, rather than 24.5^oC when the TEC is set to 10.72kΩ
• We'll keep an eye on the performance and the amount of noise hopping as 
• While it's good to have reduced the amount of mode hopping, it doesn't seem to improve the actual CRS performance, which is as expected given the NRS laser didn't improve the performance. At this point it seems like the excess noise isn't from the laser itself or the thermal regulation of the laser and is from something else.

Fil, Betsy

Today Fil and I did a quick repeat of T2200048 HAM7 ground loops check just before doors are going on.

Last checks were done:

Feb this year by Camilla/Sheila https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=89048

Feb 2022 Fil/me https://alog.ligo-wa.caltech.edu/aLOG/index.php?callRep=61738

Keita had done them prior, hence the document.

We basically found the same results as Camilla/Sheila namely:

• ISC_SQ_479 and ISC_SQ_480 have pins 13 and 23 connected 
• ISC_SQ_483, ISC_SQ_303 and ISC_SQ_481 have pin 13 and rack ground connected 

All the rest were "open".

In our PRMI locking today, Sheila had me compare some signals from today to a past PRMI time and pointed me to alog91238. We weren't sure however if these numbers made sense, so I found another PRMI time from November (specifically Nov 26th, GPS 1448216615, PRMI ASC converged) and re-did the comparison to today.

WP 13511
FRS 33242

The electronics for the IFO analog cameras were uninstalled. No impact to the PSL and building cameras (access sytem). Analog cameras were left installed, available for local monitoring. The single fibers used to connect from each end station to the corner station are now available/spares. The MSR Video Rack 7 is mostly empty.

F. Clara, J. Figueroa

Ryan C, Rahul

This unit will be shipped to CIT for ROC measurements on Zygo interferometer. This will then be return to LHO and stored in the desiccant cabinet as a spare ZM5 unit.

We removed the broken PZT and replaced it with a new one sent by Camille.

The strain gauge resistance  was measured to be around 700 ohms and 360ohm and the PZT capacitance was around 20 uF.

Details - s/n 02, mirror pre-load value = 65 in-lb.

Masayuki, Sheila

When we step the alignment sliders in pitch or yaw on PR2, we see 1 Hz ringing for 15-20 seconds.  

I copied the OPO TEC controller code and modified it to use for the JAC heater.  

The controller uses the H1:JAC-HEATER_DRV_VSET_OFFSET channel to add its control output to the heater.  The controller gain needs to be negative.

Atteched a screeshot of the new screens.

SQZ finished in HAM7 this morning, I've now unlocked, rebalanced the table and taken ISI close-out tfs. I believe it is a known issue with this chamber, but the resonances aren't as clean to resolve as they generally are for other tables, but todays measurements look very similar to my previous measurements. For the attached plots, refs 0-5 are the l2l gs13 tfs from February this year, 6-11 are from today. I think we are okey to close.

Sheila, Camilla, Ryan

After yesterday 91497 and today's checked we are finished with HAM7, it's been handed over to Jim for SEI checks. 

Sheila aligned the IFO in single bounce off ITMY to the OMC:

• Locked SRY (with ALIGN_IFO GRD)
• AS centering offloaded (using ALIGN_IFO GRD)
• Aligned SRM, Sheila had to move SRM a lot to get beam on AS_AIR camera
• Fine adjusted alignment of SRM to get SRY to lock
• Used SRY  locked in ALGIN IFO GRD but the WWFS centering failed:
• SRC1 Pitch seems to have a sign flip or similar and is;nt working. Sheila closed SRC1 YAW and SRC2 Pitch and Yaw and is by hand moving SRM Pitch to zero SRC1 Pitch error signal. This did help the buildups. Maybe the sign flip was just as we started too far away.
• Offloaded alignment by manual-ing to ALIGN IFO OFFLOAD_SRC_ALGINMENT and offloading DC centering by manual-ing to OFFLOAD_AS_CENTERING
• Now are happy with output arm.

Check SQZ alignment with this SRM/OMs alignment:

• Misaligned SR2 and SR3 and injected SQZ beam.
• Ran our modified SQZ ASC 90742 using ZM4 and ZM5 (which now have a lot more range 91431), this was able to center in AS_A,B. Not too far from OMC A and B.  See attached.
• We offloaded the SQZ ASC using SQZ_MANAGER state OFFLOAD_SQZ_ASC

Backscatter test, repeating 88609:

• Misaligned SRM to get single bounce IFO beam to the OMC
• Locked OMC
• Increased input power to 50W
• Turned on ISS with IMC_LOCK grd ISS_ON
• Ran /sqz/h1/Templates/dtt/OMC_single_bounce_scatter_check_August13.xml
• The background noise looked worse than in January 88609 so, we tested with and without the ISS, the ISS was helping, we also have an earthquake passing through. 
• We put an 1 Hz excitation of 1000 counts amplitude on ZM5 TEST,
• Could not see a scattering shelf as in December, see attached, this is expected as in the January vent this should have been fixed. 
• Plot attached, no scatter shelf visible, the large peaks we expect are from the ISS array not being well aligned.

We have completed all HAM7 close out tasks as in E2600157. Only thing left is that we may repeat 88609 backscatter tests tomorrow before SEI closeout tasks. Rahul and Ryan C completed SUS closeout measurements 91500.

• Out of OPO (before A:DC1): 1.304mW with standard deviation 0.4uW
• On SQZT7 HD path: 1.215mW std 0.5uW
• Out of OPO: 1.284mW std 65 uW
• On SQZT7 HD path: 1.215mW std 0.5uW

This is an update I've been meaning to put in for a while, but Sheila reminded me of it this morning. The IMC_LOCK Guardian will now jump to 'FAULT' if it sees JAC is unlocked and wait there, much like it does if the PSL isn't ready.

To do this, I moved the 'JAC_LOCKED()' function from the JAC_LOCK node into ISC_library.py so that both the JAC and IMC nodes can use it and it would only need to be changed in one place, and I used the function in a decorator in the IMC_LOCK node (again, much like the PSL check). All changes loaded and committed to svn.

TITLE: 08/13 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: CALM
    Wind: 5mph Gusts, 3mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.08 μm/s 
QUICK SUMMARY:

HAM7 will be a focus today with quick SQZ backscatter measurements (Rahul gave the thumbs up for SUS yesterday) and then longer SEI suite of health checks by Jim before potential close-out for sealing up HAM7 (which means lots of activities in the East Bay with Forklift/crane/other noisy activities).

IFO work with continue with Masayuki.  CRS work continues. 

On the Reservation System, I don't see "LVEA Local" laser Hazard, but yesterday we had local laser hazard for HAM7. 

Smoky day continue (although you can faintly see Rattlesnake).  This morning has shown a slow trend down in AQI to 148 (orange) from a peak of 165(red) overnight...yesterday at 10am we were at 11AQI (green).

Summary

PRMI locked!!
The MICH loop was reworked, the PRCL gain was raised, and the REFLAIR demodulation phases were tuned. The guardian has been updated to the new nominal.

Loop adjustment

After aligning BS and PRM using PRX and MICH, I first tried to lock with ISC_DRMI as it was, changing nothing. It never caught after about 20 minutes of waiting in total, split between yesterday and today.

So I went back to the MICH loop. With PRM misaligned and MICH locked, I measured the open loop gain. The UGF was at 5 Hz and the phase margin sat around 20 deg across 5–10 Hz. So, I decided to modify the MICH loop and push UGF up to 10 Hz with reasonable phase margine.

The largest phase eater was the ELP35 in FM2 of BS_M3_LOCK. I loaded an ELP200 into FM3, which was free, and used it in place of the ELP35 in FM2. That loosened the phase roll-off enough to give about 40 deg of margin at 10 Hz.

Back to PRMI. MICH1 and MICH2 also carried several low-pass filters, so I switched all of them off, and it locked within a few minutes. Once locked, all of the low-passes could be switched back on without losing lock.
Repeating this, it locked within a few minutes every time.

With the lock holding I measured the MICH and PRCL loop gains. MICH showed gain bump above 10 Hz, and the PRCL UGF turned out to be only 20 Hz. Doubling the PRCL loop gain brought its UGF up to 55 Hz, and the MICH gain bump went away. This was the most stable state I found, and the time to reacquire came down to 1–2 minutes, so I took it as the nominal and edited the guardian at this point.

Servo change summary

Filter changes

Guardian edits

REFLAIR demodulation phase

Last, I tuned the REFLAIR demodulation phases. A 50 Hz excitation of amplitude 3 was injected into PRCL1 ERR, and the phases were adjusted to minimise the peak in RF9_Q and RF45_Q. The I peak heights did not change much.

OLG

A final open loop gain measurement gave:

Both open loop TFs are attached.

Summary

We have calibrated the two JAC steering actuators the PZT (IO_MB_M4) and the JM1, in μrad per drive count at DC. The scale comes from the second harmonic of the cavity transmission under a dithered drive, which is insensitive to DC misalignment and so needs no external angle reference. 

Method

By expanding the injected field in the cavity's own eigenmode basis, we can describe the misaligned as,

Ein(t) = E0 + δ(t) E1

with E0 the cavity's TEM00 mode and E1 the TEM10 (pitch) or TEM01 (yaw) mode, orthonormal. As long as the misalignment is small enough comparing to the beam size, the single complex coefficient δ carries the whole misalignment on that axis: its real part is a transverse displacement in units of the waist size, its imaginary part an angle in units of the divergence angle. Only the TEM00 is resonant, so the transmitted power follows the fraction of the input that sits in E0, i.e. 1 − |δ|2 for |δ|2 « 1.

Dithering a steering actuator makes δ oscillate about whatever value it already had:

δ(t) = δofs + δa cos(2πft)

where δofs is the static misalignment already present, and δa is the dither we deliberately applied, which is exactly the quantity we want in order to calibrate the actuator. TRANS signal (1 − |δ|2) can devided into three components with its frequecies:

The static offset drops out of the second harmonic algebraically. 2f therefore delivers |δa| with no reference to the alignment state we happened to be sitting at, and with no external angle standard. The DC and f terms, the two one would reach for first, are both contaminated by it.

This is the whole point of the method, and it is directly visible in the plot. adding a static offset grows the 1f line by +528 % while the 2f line moves by +8 %, its own measurement noise.

Measurement

I proceeded 4+1 measurement in total with the JAC locked. For each measurement, one actuator axis was dithered at 11 Hz, with the excitation injected on the channels below and the drive read back on the corresponding _OUT. I excited JM1/PZT PIT/YAW per one measurement, and the other one is the PZT_PIT excitation with static offset (30 cnts) to demonstrate that the 2f peak is not affected by the offset. Transmission was read on H1:JAC-TRANS_A_LF_OUT.

|δa| is calculated from peak heights of the transmission at 22 Hz, converted to a mirror tilt using the local beam radius at each actuator from the current JAC reflected-path layout model (alog91472 comment), and calibrated into DC responce using each actuator's frequency response as measured (described below).

Results

The 11 Hz column is what the dither actually produced; the DC column is that value divided by the actuator's own response at 11 Hz, and is the number to use for a DC gain. 

Appendix

Actuator frequency response

The frequency response itself comes from a separate set of four broadband actuator-to-wavefront-sensor records (300 s each, one actuator per record, see atatched plots), from which the JM1 suspension resonance and the PZT drive pole are fitted. Only the shape of those transfer functions is used; their absolute scale plays no role in the calibration.

The fitted frequency responses are:

• JM1 — complex pole pair, f0 = 2.00 Hz, Q = 7.7 (PIT) and 1.80 Hz, Q = 5.4 (YAW)
• PZT — single real pole at fp = 1.24 Hz (PIT) and 1.30 Hz (YAW)

AOI compensation

Both actuators sit at a design AOI of 45°, and the rows above include the geometric correction that follows. A tilt whose rotation axis lies in the mirror surface and in the plane of incidence steers the beam by only 2θ cos(AOI), against the full 2θ for the axis perpendicular to that plane. At the PZT the suppressed axis is YAW in the cavity-referred channel naming (the HAM1 periscope exchanges the transverse planes downstream of it); JM1 sits after that periscope, so for it the suppressed axis is PIT. The assignments follow from each mirror's orientation, and the correction uses the design 45° rather than a value fitted to the measured ratio.

Cross-checks

• JM1 against its own OSEM signal. I compared the numbers above with the OSEM output with a rough single DC-step reading. The difference between the calibration factor are: 1.17× (PIT), 1.02× (YAW). 
• PZT against its design value. The design chain is APZT = 500 μrad/V (T1500342) driven through an 18-bit DAC (±10 V differential, i.e. 20 V over 2¹⁷ counts) and a differential-to-single-ended board (D1100457 v2, unity gain, read off its schematic), giving 0.076 μrad/cnt. No further driver gain applies on top, since the T1500342 figure is referenced at the controller's control input. Our result sits at 1.09× (PIT) and 1.04× (YAW) of this designed value.

R. Kumar, S. Dwyer, C. Compton, R. Short

Following the work done yesterday adjusting the preload on the ZM4 PSAMs (alog91471), Rahul and I set about adjusting it further today to get our calculated projected beam size on SRM close to where we want it. Using the same procedure as yesterday, I turned off the ZM4/5 PSAM drive chassis, Rahul went into HAM7, locked down ZM4, torqued the preload about 1/8" of a turn (it's hard to quantify a torque spec in this manner), then finally unlocked the suspension. I moved the ZM4 pitch alignment slider about -1400 counts to realign the beam on SQZT7 to our alignment irises as a result of this torque adjustment. I then proceeded to take a couple of beam profiles on the table with the M^2 device to see where we landed. This plot [initial] shows the difference between before and after this adjustment in terms of the projected beam at SRM with a few different PSAM settings on ZM4 and ZM5. The four points I took here informed us that we could stand to torque ZM4 a bit further to hopefully line up with the center of the plot.

Rahul went back into HAM7 and torqued another 1/8" and I took another couple of profiles after (I did not need to move ZM4's alignment sliders after this adjustment). I took a total of nine profile points here, all of which can be seen compared to other measurements today on this plot [full]. Since there are points in the bullseye, we decided to stop here and that this is where the ZM4 preloading will stay. This plot [final] shows just the beam profiles taken at our final preloading position.

Tomorrow we will move on to final closeout checks in HAM7.