This morning we continued to use the crane that Camilla and Ryan devised to try to get more reliable power budgeting measurements on the VIP.  Our previous measurements with the power meter held in a hand and hovering over the table consistently showed that we have something like 4% extra losses in HAM7, but they have not been repeatable enough for us to track down the location of the losses.  The crane set up helps us set the angle of the beam profiler head by using a clamp on the post, and also gives us much more steady measurements of power, so we were able to make some progress in identifying the location of losses.  However, we think that the power out of the OPO was drifting by 1-2% during these measurements, which makes the measurements less reliable for finding losses.  

We do think that we have about 0..8% loss at B:L2, where the difficult to align apperture stop is.  This apperture stop catches a rejected beam from B:P1 which is scattered light from the interferometer, so we need to keep it.  We looked for space to move it off the lens mount onto it's own separate mount, but the platform is very crowded with bases and dog clamps in this area, so that would not be an easy solution.  

For the naming of optics see:  D2000021

• (location A) after SFI1 return (before BM1): 1.251mW. (readjusted crane and centering of beam on power meter)
• (same location as A) Moving FC1 and watching SFI1 Return power. Starting P 225, Y -156 (We do not see obvious evidence of clipping in SFI1 on the return path in this data).  
  • 205 Pitch  1.247mW, STD dev 0.59uW
  • 225urad Pitch   1.247mW, STD dev 0.51uW
  • 245urad Pitch   1.247mW, STD dev 0.88uW
  • -156urad Yaw 1.246mW, STD 0.66uW
  • -136urad Yaw 1.246mW, STD 0.57uW
  • -176urad Yaw 1.243mW, STD 0.54uW
  • Starting 1.246mW, STD 0.5uW
• (location B) between SFI1 polarizer and rotator (on way to FC): mean 1.315mW std: 0.41uW.  Comparing this to above numbers it implies we have a loss of 4.9%, 5.2%, or 3.4% using number below, where we expect 2%
  • We decided to measure here instead of right out of the OPO because we were concerned that the slight angle of the beam coming out of the OPO might have been making it hard for us to put the power meter head perpendicular to the beam, and it was easier to get the angle right in this location.  In the end we got similar powers and loss estimates measuring here as measuring right out of the OPO.
• (same location as A) after A:P1 : 1.269mW STD dev 1.4uW; unlocked reloacked OPO retook to be 1.270mW STDdev 2.3uW;  1.270mW STDdev 1.7uW. Implies loss of 3.5% where we expect 2%
• (location C) after B:L1: 1.260mW std 2.1uW  1.259mW std 1.5uW 1.258mW 1.8uW 1.260mW 1.2uW Implies 0.8% loss from B:L2, probably clipping on apperture stop.
• (repeat of location B) back to between SFI1 polarizer and rotator (on way to FC) 1.330mW std 0.66uW 1.329mW std 0.67uW 1.329mW std 0.46uW  Power must have drifted up 1% since our first measurement here.
• after SFI1 before A:L2 : 1.327mW std 0.91uW  1.328mW .66uW 1.326mW 0.80uW 1.324mW std 1.1uW This implies very low loss from SFI1's rotator and 2nd polarizer, although it is possible that the rejected beam from A:P2 could also be on the power meter in this location, we could not identify that beam on a card. If the apparent loss of about 1% from each pass of SFI1 is really from misrotation the rejected beams would contain about 10uW, which we could search for more thourughly with the lights off using an IR card with a viewer.  
• after A:M3 1.321mW std 0.37uW; 1.321mW std 0.52uW; 1.320mW std 0.6uW; 1.320mW std  0.5uW Implies 0.5% loss probably at the aperture stop attached to A:L2.  
• back to after SFI1 before A:L2: 1.305 std 0.7 1.305 mW std 0.7uW 1.316mW Power is drifting enough to make these measurements confusing. 

The UPS for the EY Access system that powers the network switch a camera failed this afternoon. Power to the cameras and switch was bypassed for now.

Sheila, Ryan S, Camilla, Rahul

This morning Fil and Rahul go the ZM5 chassis working, 91431. Ryan checked the Strain gauge resistors didn't need adjusting after ZM4 preload adjustment 91416.  This afternoon we used the iris at ZM5 and irises on SQZT7 to realign ZM4 and ZM5 after this chassis swap and ZM4 offload. New ZM4 ans ZM5 settings: attached.

This morning Sheila and I checked more power budgets using craning over the OPOS. Sheila has the numbers but we convinced ourselves that the aperture at A:L2 is causing us to lose up to 2% power. But the aperture at B:L1 we are not clipping as we could not increase the power through it by moving FC1 (stepped ~20urad and then took the mean of 10s of data on the Thorlabs power meter).

TITLE: 08/06 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: Ryan S
SHIFT SUMMARY: Input alignment work in the morning, then the LVEA was transitioned to laser safe for some vacuum work on GV6. HAM7 crew got closer to closeout today.
LOG:

• 1450  VAC gauge PT180 tripped off.

Started going through the list of tests from G2601523 to find/reduce the CRS noise.

Dark test (i.e. turning off the CRS laser)

• Added offsets matching the raw PD inputs when the laser was on (1S: -1307, 1C: -374.22, 1M: -2813.2, 2S: -1243.43, 2C: -2309, 2M: -113.725) in order to make sure the atan function gave back real data.
• The laser was off and the offsets were added at 10:35 PST (1470072968.0) 
• Took about 1 hour of data for spectra
• From my understanding, it looks like the dark noise/ADC might be limiting at the higher frequencies (>5Hz), but doesn't really account for much below ~5Hz. (Spectra attached, purple and oragne is dark, blue+green reference)
• dtt template saved in /ligo/svncommon/SeiSVN/seismic/HAM-ISI/H1/HAM3/CRS/Templates/dtt/CRS_HoQI_Dark_spectra_26-8-06.xml

Unplug HoQIs to get ADC Noise

• Unplugged HoQI's from pre-amp, kept same offsets from dark test (above) at 11:46 PST (1470077241.5) 
• Similar results as with the laser turned off (Spectra attached, red and black line is unplugged)
• dtt template saved in /ligo/svncommon/SeiSVN/seismic/HAM-ISI/H1/HAM3/CRS/Templates/dtt/CRS_HoQI_Unplugged_spectra_26-8-06.xml

Next steps are to add some copper on top of the laser to see if that reduces the noise, and then looking at the impact of the motion of the out of vacuum fiber once the LVEA is safe. The HoQI's will be re-connected to the pre-amp and laser turned back on so Jim can take some more transfer functions.

Fil and Oli had already done this work yesterday, but Oli's result (posted in alog 91411) indicated that something was not right with ZM5 CD chassis. 

This morning Fil and I replaced it with the original chassis (was earlier used for ZM5 with 1.2kohm resistor) - however, Fil installed 100 Ohm resistors on this. 

Attached below are the screenshots for ZM5 L, P and Y dof. and they looks healthy - magnitude and peaks are in their place. 

ZM5 chassis installed today - D1100687, SN  S1200611 

Outgoing chassis - D1100687, S2001198

This has been wrong for forever, I fixed it at one point a long long time ago (alog 29798) but apparently didn't put it in SDF.

Anyway, FM4 of H1:PSL-ISS_SECONDLOOP_QPD_SEG filters named 0.4:40 was OFF, it should be ON all the time like in the attached screenshot.  When it's wrong the signal looks noisier than it actually is and is annoying even though it's not used for control and doesn't matter during observing.

I accepted the change in the SDF.

I changed the heater power from 0.8 to 2W, and the temperature increased up to ~25.4 degrees. The heater guardian setpoint was also changed to 25.41, and engaged at 9:07AM. 

TITLE: 08/06 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: 0mph Gusts, 0mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.08 μm/s 
QUICK SUMMARY: SEI_ITMX is in DAMPED as Corey noted yesterday. A few dust alarms went off early this morning, but they all seem to be coming down. AQI is still high. CDS all looks OK.

Summary

We performed a high-power test of JAC. The input power was ramped from 2 W to 62 W using the Guardian power up/down states, and JAC stayed locked through the entire ramp without any problem.

To quantify thermal effects on the mode matching, cavity scans of both the IMC and JAC were taken at 2 W and at 62 W. The main conclusion is that the thermally induced mode-matching change is negligible for both the IMC and JAC.

Other checks

JAC stayed locked through the entire ramp from 2W to 62W. The OLG was measured at 2W and 62W, the difference was about 3dB, and this increase is caused by the discrepancy of the power normalization value and actual power to the JAC REFL PD. 

During the following test JAC lost lock a few times (deliberately and otherwise); in every case the trigger PD responded correctly and the shutter closed as designed. The ASC loops were also closed during the power increase and worked without issue.

IMC scan

The analysis follows the method already posted in alog 88984. For the 62 W scan the readout was switched to POP_B : MC2_TRANS starts to saturate at high power, and a saturation-induced tail dragging is visible in its response, which would contaminate the analysis. (Actually, POP_B has also the contamination, but I concluded that we can ignore that effect, since we can't see any 2nd order peak in the scan as discussed below.)

The IMC mode matching is at a very good level to begin with, and the thermal lensing improve the mode matching: the second-order mode content are 0.22% for 2W and <0.3% (62 W). As the attached scan plots show, there is no observable second-order peak in 62W plot, so the upper limit of 0.3% was estimated by the noise floor. Note taht the first-order modes are caused by intentional misalignment. 

JAC scan

To estimate the thermal change for JAC, we also scan the JAC PZT. Scan parameters: PZT driver swept 51–311 V (triangle, 10 s period), 300 s at 2 W and 60 s at 62 W, reading channels JAC-PZT_DRIVER_VOLTS  / JAC-TRANS_A_LF.

The mode mismatch is 1.1% for 2W and 1.0% for 62W. Again, no significant thermal change. Since the mismatch is visible at the >1% level, moving the PSL mode-matching lens could probably improve it somewhat; whether we do this is left for later.

As a byproduct, the 43 MHz modulation index was extracted from the scan with a matched filter on the lower sideband (62 W, 12.7–13.5σ): m ≈ 0.009, consistent with the expected 0.01. 

Earlier I took ZM4/ZM5 transfer function measurements with the new coil driver chassis but with the old AntiLP coil driver conpensation filters still installed in COILOUTF. I now went and took another set of transfer functions on ZM4 with the new set of coil driver compensation filters (since ZM5 is broke(91425), and it does look like these are giving us the response we want (L,P,Y). There is still a small discrepancy between the magnitudes, but it's about half as much as what it was before. I'll process these new measurements tomorrow.

I've also installed these filters and loaded them in for ZM5 for when we swap out a new modified coil driver tomorrow.

Here are preliminary pass/fail test results for the modified HAM-A chassis. In 84454 we found out we hadn't done the modifications yet that had been outlined in E2400048.

First I have the results for the newly installed ZM4 and ZM5 coil driver chassis, then the spares, which don't have final results since they aren't assigned to AOSEMs or BOSEMs yet, then the results for the BHD electronics, which aren't being used but have already been installed in the Mechanical Room Mezzanine.

When only one channel is listed as bad, they could actually have an issue or it could just be an error while taking the measurement for that chanel. When multiple channels are bad, that seems more like a chassis problem.

Scripts used to run all of these are in /ligo/svncommon/SusSVN/sus/trunk/electronicstesting/lho_electronics_testing/coildriver/ECR_E2400048/Scripts/, and final results for those who have them are found in /ligo/svncommon/SusSVN/sus/trunk/electronicstesting/lho_electronics_testing/coildriver/ECR_E2400048/Results/.

Masayuki Nakano, Khanh Vu

This afternoon we worked on balancing the wavefront sensors for JAC. As shown in the plots below, the coupling of the length signal into the pitch and yaw channels of both WFS A and WFS B is significantly reduced after the adjustment, indicating that the balancing was successful.

To measure the length coupling, we injected a 0.1 excitation into the JAC length loop error point at 8 Hz. The 8 Hz peak appeared in both the pitch and yaw channels of WFS A and WFS B, indicating an imbalance among the four quadrants of the wavefront sensors. To reduce this coupling, we modified the WFS input matrices, which convert the four sensor segment signals into pitch and yaw signals. Instead of using equal weights of 1 for every segment, we adjusted each weight based on the measured imbalance.

We first monitored the signals from all four segments of each wavefront sensor and calculated new matrix values. For each sensor, we summed the four segment signals and divided by four to obtain the average signal that each segment should ideally receive. We then calculated the fractional deviation of each segment from this average and used it to determine a correction factor. The new matrix entry for each segment is given by:

New weight = 1 − (Average − Segment)/Average​

For example, the measured signals for channel I of WFS A were:

The sum of the four segments is 40.96, giving an average of 10.24. Segment A_I1 is 0.08 above the average, corresponding to a fractional deviation of approximately 0.008 (0.8%). Its new matrix weight therefore becomes approximately 0.992. Since this segment receives slightly more signal than the average, its weight is reduced accordingly. The same calculation was applied to all four segments of both WFS A and WFS B, and the updated matrices were loaded into the system.

The comparison of the pitch and yaw signals for channel I of WFS A and WFS B is shown below. The 8 Hz length coupling is reduced in all cases compared to the original matrices, demonstrating that the new balancing improves the wavefront sensor performance.

Keita, Louis, Elenna

Today Louis and I set out to measure the beam spot position on MC2 using A2L. We spent some time doing wrong things to make this measurement, until Keita came along and helped us figure out the correct way to do this.

Here is our correct method:

• set up an excitation on the MC2 M3 Dither for either P or Y
• We chose 8 Hz, starting with a 10 ct excitation and working up to 100 ct depending on the dof and the A2L gain value
• Measure the coupling from MC2 M3 dither to IMC L at 8 Hz, and adjust the MC2 M3 Drivealign A2L gain

We did all of these measurements with IMC ASC engaged, and no offset on MC2 trans QPD, so the beam "should" be centered on MC2.

For both pitch and yaw, we were able to observe a flip in the sign of the MC2 M3 dither/ IMC L transfer function. Because I set up the measurement in that funny way, this actually meant we needed to maximize the transfer function instead of minimize, which is a little confused (I figured this out after having saved several references, sorry). Luckily, we were able to see the sign flip as further proof we were moving through a minimum value.

The results indicate that a P2L gain of -0.85 and a Y2L gain of +0.5 minimized the coupling.

I found this alog I wrote which references several other alogs about measuring the beam position using the A2L gains, 76754. I wrote it about PR2, but MC2 and PR2 are the same suspensions, so the results should be the same.

For a Y2L of 0.5, the alpha factor is 0.0239 (unclear if this should be positive or negative), which means d = 39.28 mm * 0.0239 = 0.94 mm; we are miscentered in yaw by less than 1 mm in some direction.

For a P2L of -0.85, the alpha factor is -0.0405, d = 39.28 mm * -0.0405 = -1.6 mm. Keita and I had a debate about what this could mean. I claim that the P2L gain that matches a centered beam could be different than zero depending on where the suspension wires are attached to the mirror (this is true for the QUADs), but he does not think that should be the case if we are measuring at 8 Hz, above the suspension resonances. Therefore, my claim is that we don't know exactly how miscentered we are in pitch until we figure out how to account for that offset. Keita claims that does not matter. We will reconvene tomorrow to discuss further.

Either way, it it could indicate that MC2 trans QPD is not exactly level with the center of MC2 mirror.

Overall, being less than 1 mm miscentered in yaw is not so bad, and within our tolerances for beam centering while working in chamber.

I attached screenshots of my dtt templates during these injections, labeled by the A2L gains.

Camilla asked me to take some health check transfer functions on ZM4 and ZM5 since they recently had their coil drivers swapped for modified 100 Ohm output impedance drivers (91407). SQZ team had had to lower the COILOUTF filter bank gains from +/-1 to +/-0.08 due to saturations that they had been seeing after the driver swap.

I moved the COILOUTF gains into FM10 and called them drivercomp (accepted as ON in SDF). I then took health check transfer functions for ZM4 and ZM5 with their previous COILOUTF AntiLP filters on (which I believed to be the wrong filters). ZM4 looked good and was at a similar magnitude as before, but ZM5 is now lower in magnitude - 8% of what it used to be, which does line up exactly with the coil driver and gain change, but we would expect for both ZM4 and ZM5 to have reacted to these changes the same.

Settings
- ISI locked and tripped
- SUS in HEALTH_CHECK
- DAMP OFF
- COILOUTF FM6: zpk([0.9;211.883],[9.99;20.99]) (old, wrong?? compensation)
- COILOUTF FM10: gain(0.08)

ZM4
Data
/ligo/svncommon/SusSVN/sus/trunk/HXDS/H1/ZM4/SAGM1/Data/2026-08-05_1900_H1SUSZM4_M1_WhiteNoise_{L,P,Y}_0p02to50Hz.xml
r13101
Results
/ligo/svncommon/SusSVN/sus/trunk/HXDS/H1/ZM4/SAGM1/Results/2026-08-05_1900_H1SUSZM4_M1_ALL_TFs.pdf
r13102

ZM5
Data
/ligo/svncommon/SusSVN/sus/trunk/HXDS/H1/ZM5/SAGM1/Data/2026-08-05_1940_H1SUSZM5_M1_WhiteNoise_{L,P,Y}_0p02to50Hz.xml
r13103
Results
/ligo/svncommon/SusSVN/sus/trunk/HXDS/H1/ZM5/SAGM1/Results/2026-08-05_1940_H1SUSZM5_M1_ALL_TFs.pdf
r13104

Coil driver thoughts

These are actually our first two supensions with the HAM-A 100 Ohm output impedance coil drivers here at LHO (we have had a few with 1.2k Ohm output impedance). We discovered that we hadn't made of the modifications requested in IIET:30349 in 84454. I am pretty sure that the AntiLP filter modules in the COILOUTF filter banks should now go from zpk([0.9;211.883],[9.99;20.99]) to zpk([0.5;3174],[52.32;50.77]) (T2100410), but we don't have any other 100 Ohm CDs here to compare that to, and looking at LLO's filter banks for suspensions they claim have this modification for 100 Ohms, yet they still have the old compensation filters installed.

I did try to install the AntiLP filter that I believed to be the correct one, but doing that with the COILOUTF gains at +/-1 was definitelty not working. When there's some free time I'd like to try reinstalling the zpk([0.5;3174],[52.32;50.77]) filters but with the gain at the 0.08 that it was changed to? I don't see why we would need to do this since the 1.2k Ohm Coil Driver suspensions don't have this factor, but maybe I'm missing something that is specific to the 100 Ohm output impedance drivers.

Keita Kawabe, Jennie Wright, Masayuki Nakano, Khanh Vu

Below is a summary of how we closed the JAC ASC loops, including our measurements of the sensing and input matrices, the open-loop gain measurements, our work on the IOT1 table, and the final closing of the loops.

We attempted to measure the sensing matrix three times. During the first attempt, we observed strong cross-coupling between the pitch and yaw channels. However, we did not account for this coupling correctly because we inverted the full 4x4 sensing matrix, including the pitch-yaw cross terms, and then extracted the relevant values from the inverted matrix.

The second attempt was more successful. We removed the cross terms and reduced the 4x4 matrix, which would require 16 inputs, into two separate 2x2 matrices for pitch and yaw, requiring only eight inputs in total. We then inverted the two smaller matrices separately. There was also some confusion about the matrix labeling, but Masayuki noticed that the input and output ordering changes when the sensing matrix is inverted, so the rows and columns needed to be labeled accordingly. This proved to be correct. However, the newly calculated matrices were still not good enough because the PZT and JM1 responses in yaw were too similar. This was problematic because we wanted their signals on the two wavefront sensors to be well separated.

Therefore, we went to the IOT1 table to check the alignment. Masayuki made an important observation that the beam was being clipped at the shutter, with approximately half of the beam blocked on the left side. This explained why we were having more trouble with yaw than pitch, since the clipping affected yaw much more strongly.

After aligning the shutter, we measured the sensing matrix for a third time. The result was much better: the PZT and JM1 yaw response vectors were separated by approximately 45 degrees in the WFS basis, while the pitch response vectors were separated by approximately 124 degrees. Although these values are not at the ideal 90-degree separation, we determined that they were good enough and entered the new input matrices.

We then performed open-loop gain measurements and confirmed that all of the loops were behaving properly. Finally, we closed the loops and slowly increased the WFS gains from 0.1 to 1. All four loops closed successfully and worked well.

Jenne, Wanda, Shoshana, Gizem

We started very early this morning to beat the heat, and performed 'tap tests' at various points along the length of the arms to identify positions along the length of the fiber (according to DAS) with GPS positions (according to Wanda's phone).

Spreadsheet attachment is information about where along the fiber Shoshana and Gizem identified our tapping in the data, and associated time stamps.  I've also copied the spreadsheet data to a google sheet, so that we can add to it.  

We tried to do more dense taps on the 'inside of the vertex' side of the arms, where the fiber actually is.  This required some walking out in the sand along the arms, so we had sun hats and knee-high boots and plenty of water.   We also did a few taps along the road during our drive back, to get some more coarse information along the length of the arms.  At the Xend station, there were too many tumbleweeds for us to walk along the inside-vertex side of the arm, so there at EX we did our more dense taps along the road side, with the exception of the EX vault location. 

In the attached photos, you can see some examples of our tap test method.  Gerardo provided us with a scrap piece of steel that we used as a strike plate.  We also borrowed a sledgehammer from the mechanical / vacuum parts lab.  For most of the Yarm, we only did 3 heavy strikes and Gizem and Shoshana chose the strongest signal from that as our time.  Once we were on the road-side of Yarm, and then for all of Xarm, we added some light tapping that seems to have helped identify which distance bin (called a "channel" in DAS terminology) we were closest to.  The photos are also labeled with X/Yarm, and position number, which corresponds to the position numbers in the google sheet - I tried to capture features in the photo to help identify where exactly the strike plate was.

Wanda has added to the google sheet the GPS locations that she identified while we were at each tap point.

The last photo shows our used (but can be used again in the future!) strike plate. 

Travis, Gerardo, Jordan

During the closing of GV6 back in May, we noticed that there was some blow-by in the pneumatic system when trying to hard close the valve, see alog 90093. 

We were able to hard close the valve eventually but as preventative maintenance we wanted to replace the air cylinder seals, similar to GV7.

Prior to disassembly we measured the locations of the reed switches from the top surface of the bottom plate to the bottom surface of the reed switches:

Bottom Switch: 1 1/8"

Top Switch: 49 1/4"

We then disassembled the air cylinder and replaced the seals following procedure/notes collected during the GV7 repair. During cleaning of the old grease on the piston head, we noticed there were two burrs on the top of the piston, we did not notice any damage to the inside of the cylinder, but as a precaution we used a small flat file to remove the burrs. We also chased the threads on the four threaded rods with a die to aid with reinstallation. After cleaning and inspection of the cylinder tube, we found no issues or damage so we decided to continue to use that cylinder and keep the new one as a spare.

No other issues encountered, we removed the old seals, cleaned the grooves, added copious amounts of the supplied grease to the o-rings, seals and the inside of the air cylinder, and then re-assembled the cylinder tube. Pictures posted below and a final procedure is in progress and will be posted to the DCC.

We did not get a chance to cycle the valve after the seal replacement, so we will continue tomorrow with cycling the valve.

(Jordan, Travis, Gerardo)
We removed and replaced the AIP for BSC6, no real complications while doing the work.  However the joint at the AIP and the isolation valve has a tiny gap towards the bottom, we started pumping down on the system and it appears to be a solid union, we will go and visit tomorrow and see how the pressure is doing.  On a side note we did find a flex metal hose that has a leak, it has been removed from circulation.

Summary

Whatever happened to IM1, Rahul did make it better again. Reasons for improvement is unknown but we proceeded with the alignment and we're mostly done.

There is a mystery scattering or maybe clipping somewhere close to the IFI output but not on the output baffle nor DKDP baffle. It could be a scatter from the CWP surface, or a ghost beam somewhere, or something else. It will take a LONG time to diagnose this, and quite likely this existed for a long time. I'm tempted to leave it at this time. But I'll try to take some more pictures.

There's also something weird about the 1st pico mirror PIT actuator for ISS array.

We'd still like to take pictures/measurements here and there on Tuesday.

Done: ASC REFL centering

Following the morning work (alog 90525), REFL ASC censors were centered using RM1 and RM2. About ~30% of DAC range was used for RM2 (RMs_happy_again.png). FYI, using flash peak, [P,Y]=[-0.003, 0.015] for REFL_A and [-0.020, 0.001] for REFL_B. (Doesn't matter how close these are to zero as far as they're within +-0.1 or so and the SUM is decent, but it feels better to be able to get close to zero.)

Done: ISS array centering

Then we looked at the ISS array and the QPD was not centered. A quick adjustment of the second pico that is closer to the array was all it needed (keita_ISS_happy1.png). [P, Y]=[-0.03, 0.05].

Done: IFO REFL baffle (HA13) adjustment

We looked at the IFO REFL baffle (HA13) in front of the HAM2-HAM3 septum window and it was too high even though it was not clipping, so we lowered it by a couple mm. Before: lower edge height = 105.5mm; upper edge = 206.8mm. After: lower edge = 103.6mm; upper edge = 204.5mm.

This baffle was already moved by a couple mm in +Y direction last week (because the beam was closer to +Y edge). See  IFOREFL_baffle_before_relocation.jpg and IFOREFL_baffle_after_relocation.jpg though it might be difficult to see the difference from this picture.

IFO REFL beam looked like IFOREFL_HA13_baffle_after.mov after the height adjustment.

Mystery flashes seen inside IFI output baffle aperture

We proceeded to check the IFI output baffle and I was bothered to find that something that looked like clipping was visible close to the left edge of the baffle using the IR camera. See IFI_OUT_clipped_720p.mov, this is a view from +Y door. But this was less frequent than the flashing itself. In a retrospect, this was probably the reflection from the PRM when the beam was swinging to the left of the video, but anyway we did various things:   

• We got suspicious about PRM somehow misaligned, checked it on the retroreflection check iris but it was fine in YAW (it was off in PIT so changed PIT offset from -1185 to -1115, not sure if it was PRM that changed or something else, but the important thing was that it wasn't off in YAW and that this is not something that I worry about now that we have a decent headroom for RM2 DAC).
• We closed the HAM3 door cover (which did quiet down the beam motion a lot) as well as the HAM2 -Y door cover. I used IR viewer and thought that nothing changed at the time. The bright thing didn't disappear after blocking the beam between PRM and IM4, again using the IR viewer, I thought.
• However, revieweing videos shot later, I haven't found anything to the left of the output baffle after the beam motion was reduced by closing unnecessary open door covers. But that revealed the next issue.

See IFI_out_another_view.mov, this is after the beam quieted down enough and after PRM PIT was changed. The bright thing at the left side of the baffle hole is not visible any more, but you can still see bright-ish scattering of some sort inside the baffle aperture which was there even when Rahul blocked the beam between PRM and IM4. IFI_out_another_view.jpg shows the same thing but with more useful exposure. This is concerning.

DKDP baffle behind the IFI output cwp baffle looked OK (IFI_DKDP_baffle.mp4). BTW, as was reported before, it looked to us that the IFI output baffle has an offset in -X+Y direction relative to DKDP. In the video, the beam on DKDP is slightly biased to the right on average because we tried to split the difference between two baffles.

We moved IM1 in YAW by +-200urad while observing the IFI output by IR viewer to see if there is a better beam position on IFI output. It seemed to me that actually we don't have much space here.

Look at IFI.png to see how the beam is routed through DKDP, output CWP and then passes by the parking beam dump pick-off.   

• If we give negative 200urad for IM1 YAW, the forward-going beam starts to interfere with the parking beam dump pick-off once in a while and the frosted barrel of that pick-off becomes bright. This is despite that the beam looks perfectly fine when IM1 is at the now-nominal position (see parkingBD_pickoff.mov, negative 200urad IM1 rotation would mean that the beam will be like 1mm to the right in this video).
• If we give positive 200urad for IM1 YAW, I thought that +X side of the IFI output cwp baffle starts to get brighter once in a while (my theory is that this is the same thing as shown in IFI_OUT_clipped_720p.mov where the edge of the baffle clips the back-propagating beam when the beam moves too much).

We'll be better once we're in vacuum because things will be quieter and the MC alignment will be better, so no beam motion and no HOM transmission, but I have to say that the clearance here looks to be unnecessarily narrow. I will NOT touch IFI itself so the only option for mitigation will be to move the parking BD pickoff, but it will be tedious to align that pickoff to steer the beam into the beam dump on top of HAM2. Given the limited time available I'll leave it as is.

We don't know what this scattering is, maybe it's the AR reflection of CWP or DKDP hitting something, maybe it's the surface scatter of CWP. I'll try to take the video from the back of the IFI output beamdump/CWP using a big inspection mirror.

Done: IM4 TRANS centering.

Rahul used pico mirror to roughly center IM4 TRANS while I was monitoring individual segments. IM4TRANS_ROUGHLY_BALANCED.png

Done: IM4 baffle (HA12) moved

As planned. The beam originally was offset in +X direction (IM4_HA12_before.jpeg shows the original location, IM4_baffle_HA12_before.mov shows the beam position), IM4 baffle was moved a bit in -X direction (IM4_HA12_after.jpg, IM4_baffle_HA12_after.mov).

Done but not really: Picturing the picos, one concern for the first ISS pico actuator.