High power JAC test

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.

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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. 

 

ZM4 / ZM5 COILOUTF AntiLP filter updated

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.

ECR E2400048 modified preliminary coil driver test results

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/.

Rack - Height	SUS Stage OSEMs	S/N	OSEM Type	Date tested	OutImp (kOhm)	Data looking good?	Comments
ZM4, ZM5
SUS-C8, U12	ZM4	S2001194	BOSEM	2026-01-29	0p1	yes
SUS-C8, U11	ZM5	S2001198	BOSEM	2026-01-30	0p1	CH1-4 bad	first pole doesn't get close to 0 phase until we change 0.5 to above 20 Hz
Spares
--	SPARE	S2001202	--	2026-01-29	0p1	yes
--	SPARE	S2001204	--	2026-01-29	0p1	yes
--	SPARE	S2401019	--	2026-01-29	0p1	yes
--	SPARE	S2401020	--	2026-01-29	0p1	yes
--	SPARE	S2001197	--	2026-01-30	0p1	CH2 bad
--	SPARE	S1200609	--	2026-02-02	1p2	all go up above 1000Hz
--	SPARE	S1106046	--	2026-02-09	1p2	all go up above 1000Hz
--	SPARE	S2500410	--	2025-10-02	1p2	yes
--	SPARE	S2500412	--	2025-10-02	1p2	yes
--	SPARE	S2500413	--	2025-10-02	1p2	yes
Installed for BHD
SUS-M2, U42	OM0 M1 F1F2F3SD	S2001203	BOSEM	2026-01-30	0p1	CH1 bad
SUS-M2, U41	OM0 M1 LFRT	S2001201	BOSEM	2026-01-30	0p1	CH1,CH4 bad
SUS-M2, U40	OM0 M3	S2001181	AOSEM	2026-02-02	1p2	CH3 bad
SUS-M2, U38	OBS M1 F1F2F3SD	S2001200	BOSEM	2026-01-30	0p1	yes
SUS-M2, U37	OBS M1 LFRT	S2001199	BOSEM	2026-01-30	0p1	yes
SUS-M2, U35	AM1 M1	S2001179	BOSEM	2026-02-09	1p2	yes
SUS-M2, U34	AM2 M1	S2001178	BOSEM	2026-02-02	1p2	maybe? CH4 bad above 3000Hz
SUS-M2, U32	OMCAB M1 H1V1H2V2	S2001195	AOSEM	2026-01-30	0p1	yes
SUS-M2, U31	OMCAB M1 H3V3	S2001196	AOSEM	2026-01-30	0p1	yes
SUS-M2, U29	OMA1 M1	S2001177	BOSEM	2026-02-09	1p2	yes
SUS-M2, U27	OMB1 M1	S2001176	BOSEM	2026-02-09	1p2	yes
SUS-M2, U24	OMA2 M1	S1200608	BOSEM	2026-02-09	1p2	?? CH1-4 bad above 3000Hz
SUS-M2, U23	OMB2 M1	S1201155	BOSEM	2026-02-02	1p2	?? CH1-4 bad above 3000Hz
SUS-M2, U21	OMA3 M1	S1201162	BOSEM	2026-02-09	1p2	?? CH1-4 bad above 3000Hz
SUS-M2, U19	OMB3 M1	S1201165	BOSEM	2026-02-02	1p2	?? CH1-4 bad above 3000Hz

Balancing the JAC Wavefront Sensors

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:

A_I1	A_I2	A_I3	A_I4
10.32	8.39	10.9	11.35

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.

Spot position on MC2

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.

Wed DAY Ops Summary

TITLE: 08/05 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: Oli
SHIFT SUMMARY:

The main detector activities were JAC measurements, SQZ/ZM4, & input alignment.  A noisy fan for an EY SEI sent Fil & Tony out to swap the power supply (while out there we lost the SUS front end, so that needed to be restored afterword).  Other miscellanea of note:  SEI-ITMx has been at DAMPED since Tues morning (Tony noted); SUS-ITMy has been at MISALIGNED since Monday afternoon; & the TCS CO2 lasers are DOWN.

Another very smoky day (AQI close to 180 at end of shift); fire-wise, only one small fire in Pasco noted in the afternoon.  Had alarms for the LAB1 Dust Alarm a few times during the shift.

LOG:

• 1430-1825Asphalt crack sealing along X-Arm's X1 (randy)
• 1441-1530 LVEA technical cleaning (kim.dawn)
• 1500 Working on Gate phone (richard)
• 1550-2004 JAC modematching + high power measurements w/ IMC unlocked (masayuki.khanh)
• 1627-1646 Checking on AED at the FCES (HAM Shack) [eric]
• 1642-1653 Pulling chassis for ZM4+5 (fil.camilla)
• 1655-1934 HAM7 (preceded by quick HAM3 check) SQZ work (sheila.camilla)
• 1724-1827 EX EY tech cleaning; X-arm crack filling, so switched to EY (kim)
• 1728-1843 Checking POP electronics and HAM3 electrical feedthru flange (keita)
• 1748 Let blue truck w/ long flatbed of metal framing thru gate (they tried gate code + gate call, but it did not work)
• 1801 MC2 misaligned for Keita's work....will realign for Masayuki when he returns to his measurements after SQZ work is done (will need to contact Keita).  
  • 1956 MC2 misaligned again (keita)
• 1856-1903 Reseting test measurement s in PCal lab (tony)
• 1913-1925 TCS chiller check (corey)
• 1943 EY fan noise check (fil)
• 1952 cleanroom work with scissor lift (randy)
• 2034-2135 swapping power supply (noisy-fan) for EY ISI (fil.tony)
  • 2056 SEI software WD trip
  • Lost the SUS ETMy front end (dave notified us & will restore after power supply work)
  • 2129 After WD trips, SEI ETMy back to FULLY ISOLATED
• 2050-2244 ZM4 in-chamber checks at HAM7 (rahul.camilla)
  • 2058 camilla joining
• 2216 Grabbing 2nd chassis [from CER work this morning] (fil)
• Camilla & Rahul chatted with Oli (eve) shift about ZM5 & Oli also connected in the Zoom session with Elenna/Louis for the evening.

ZM4 pre-load on the optics re-adjusted to 60 in-lb

Sheila, Camilla, Rahul

The SQZ to OMC mode matching measurement results (posted in alog 91385) had indicated that something is not right with the preload value on ZM4 (s/n 1)- which was recently adjusted from 75in-lb to 65in-lb. 

To confirm the preload value on ZM4 we went back to HAM7 and using two torque wrenches we tried to confirm the pre-load value. We increased the torque values in the increments of 20-40-60in-lbs. After 40in-lbs I felt the torque wrench kept going and stopped at 60in-lb - which meant it was indeed less than 60in-lb. Using the two torque wrench I then increased it to 65in-lb, which is when Sheila suggested that we keep it 60in-lb since it will be a better fit.

Hence, ZM4 preload was set to 60in-lb and double checked using the two torque wrench (with 10% error approximately since they didn't behave exactly the same). I should get an analog (gauge dial) torque wrench rather than this springy thing which doesn't work properly sometimes.

After setting the preload, I set the suspension free and re-connected the PSAMS cable and switched ON the chassis.

The transfer function measurements showed that the suspension was healthy (please ignore the magnitude, this maybe due to incorrect filter changes after changing the coil driver impedence from 1200ohms to 100ohms) after all the work was completed in chamber.

End Y Kepco Power Supplies

WP 13490

The following power supplies were replaced at EY.

July 28 2026
Kepco Power Supply in VDC-C2 Rack, Right Slot U5-7, SEI IO Chassis 24V
Old S1300281
New S1300294

August 5 2026
Kepco Power Supply in VDC-C2 Rack, Left Slot U9-11, +24V SEI-C1
Old S1300293
New S1300274

While working in the VDD rack, the power supply for both SUS IO chassis was powered off. Dave B. restarted models, alog 91413.

F. Clara, D. Barker, T. Sanchez

ZM4 / ZM5 COILOUTF filter module changes and SUS health checks - pass?

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.

 

 

h1susey and h1susauxey rebooted following DC power supply work

The EY +24VDC power supply which powers the two SUS IO Chassis went offline. The SWWD in turn tripped the SEI DAC drives.

Fil recovered the IO Chassis and we rebooted h1susey and h1susauxey frontends. All came back with no problems and I untripped the SWWD.

Note that h1omcpi, which receives a 16k IPC channel from h1susetmy, started showing a low receive error rate on its h1ioplsc0 64k receivers. Error rate of 1-6 errors per second, occuring every 5 seconds or so.

SQZ Power Measurements using Craning for on OPOS measurements.

Sheila, Ryan S, Camilla,

Our SQZ power measurements we've taken so far seem to be unreliable: 91360, 91197. So we made a crane to hold the power meter steady on the OPOS by temporarily removing the OPO SUS EQ stop, see photo of crane before power meter was added. In brackets is the order the measurements were taken. 

We seem to get loss both at SFI1 and B:L1 aperture.

• (1) Out of OPO before A:DC1: 1.30mW
  • 2% loss through SFI1 first pass, expect 1%
• (4) After ZM1 1.275mW
  • 2% loss through SFI1 second pass, expect 1%
• (2)After SFI1 before B:M1: 1.25mW
  • 0.8% loss through B:L1 aperture, expect 0%
• (3) After  B:L1 1.24mW
  • 2.5% loss through SFI1 and B:BS1, expect 2%
• (5) After ZM4 1.21mW
  • Total from OPO to after ZM4 6.9%, expect 4%.

The power then jumped and we took the following set of measurements, but they don't make as much sense so we think the power was drifting. 

• After SFI1, before A:L2 1.34mW
• After A:L2 about 1.34mW
  • No loss at A:L2 aperture. 
• Repeating out of OPO 1.4mW
  • 4.5% loss though SFI1 first pass the second time, seems too high.
• Repeating after ZM4 1.278mW
  • Total 8.7% loss, expect 4%

Yesterday when Ryan and I set up the crane, we measured out of the OPO (1.37mW) and on the SQZT7 HD path after the lens (1.26mW)  which is an 8% loss, consistent with today's first measurement. 

*Total loss calculated as [1 - (Power after / Power before)]

TCS Chiller Water Level Top-Off (Bi-Weekly, FAMIS #81868)

Addressed TCS Chillers (Wed [aug5] 1213-1225pm local time) & CLOSED FAMIS #81868.

For measurements below, measuring from "top" of the red floaty ball.

• TCSx Chiller:  Had level of 29.7 cm.  Added 50mL for 30.0cm.
• TCSy Chiller:  Had level of 10.3 cm.  Added 30mL for 10.5cm.  
• There was no water in the small cup under the slow leak.

ASC POP_A and B seem to be connected to the wrong feedthrough

Since POP_A and POP_B QPDs didn't show any signal whatsoever when I scanned the beam going into PR2 (alog 91397), I got suspicious about the electronics.

I first went to the field rack (ISC R4), disconnected the cable (CAB_H1: IO-245) that is supposed to go to HAM3 (and to the POP QPDs) from the front panel of the transimpedance amplifier, connected a breakout board to the cable and checked the diode connection from pin 16 (common cathode for QPD1) to pin 1,2,14, 15 (anode for four segments of QPD1) as well as from pin 19 (common cathode for QPD2) to pin 4,5,17 and 18 (anodes for QPD2) using a DVM. There was no connection. 

I moved to the D3 flange of HAM3. The IO-245 cable was connected to D3-F7 and that was correct according to T2400150 as well as the redline version of D1002874.

I disconnected the cable from D3-F7, attached the breakout board to D3-F7 and checked the diode connection. Again, no connection.

I moved the breakout board to D3-F6, which is nominally to be used for "LO1 M1 RTSDxxxx" and I was able to see eight diodes between right pins. pin 16 (cathode) to pin 1, 2, 14 and 15 (all anode) showed about 0.4V only when the current goes from anode to cathode, nothing in reverse direction. Same thing for pin 19 to pin 4, 5, 17 and 18.

We don't have LO1 inside HAM3 (if LO1 means a new suspension for BHD or something) for now, so I'm 100% confident that the POP QPD cable is somehow plugged into D3-F6 instead of D3-F7 inside.

I connected the in-air QPD cable to D3-F6. I'll be testing if the QPD channels respond to flashlight/illuminator/laser pointer.

Summary of JAC ASC Loops Closing

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.

Input alignment work

Keita, Louis, Elenna

Today, we proceeded to look for the input alignment, given all the changes that occurred in HAM2 during the ISS install, 90545. Although we have been able to lock PRX, we have not yet seen any beam on ASC-POP_A or B QPDs (they capture the forward POP beam).

To start, we locked the JAC and IMC, and aligned PRM. We could see the usual beam on the ISCT1 REFL camera. We noted that the beam position on IM4 trans QPD was far from center, about 0.26 in pitch and 0.66 in yaw. The IM4 trans NSUM was about 1.825 W, which is similar to a pre-vent value of 1.842. At this time the IM3 sliders were P: 40.3 and Y: 655.6. We confirmed that the IM sliders were where we expected them to be set due to the vent work.

I moved IM3 sliders to center the beam on IM4 trans QPD, so new slider values were P: 103.3 and Y:472.6. Then, following Keita's direction, I proceeded to measure a transfer function of IM1 P and Y and IM3 P and Y to the IM4 trans NSUM as a way to quantify possible clipping in the input path. IM1 coupling should indicate clipping somewhere along the IFI, which includes some baffles. IM3 coupling should indicate clipping on the baffle between IM3 and 4.

The first four screenshots show those results, which I obtained by driving a 30 ct excitation from the test bank of each suspension dof at 8 Hz. IM1 P, IM1 Y, IM3 P, IM3 Y

Next, Keita turned off the IMC ASC and moved JM3 to bring the beam to a position on MC2 trans that recreated the beam position he found during the vent. He set a yaw offset of -0.64 on MC2 trans and then re-engaged the IMC ASC. After the ASC converged, I recentered the beam on IM4 trans using IM3 again. We confirmed that the NSUM on IM4 trans returned to 1.825. I reran the same coupling test above and we saw that for all four dofs, the coupling to IM4 trans NSUM increased. This is evident in both increased coherence and coupling value at 8 Hz.  IM1 P, IM1 Y, IM3 P, IM3 Y

Then, Keita flipped the sign of the yaw offset to +0.64, since there is some confusion about which way the sign goes on that QPD. I recentered the beam again on IM4 trans, confirmed the NSUM came back to 1.825 , and reran the coupling measurement. The results show that for all four dofs, the coupling is decreased to below the starting value, shown in both the coherence and coupling value. IM1 P, IM1 Y, IM3 P, IM3 Y

It's possible that we are confused about the sign on MC2 trans, so that the first offset Keita tried actually went to the wrong position.

Another confusing point is that we see coupling in both pitch and yaw, and beam movement in both pitch and yaw. However, the beam translation we did was yaw only, to relieve yaw clipping.

Since we had found what we believe was a better beam position in HAM2, we checked the REFL alignment. With PRM aligned in this alignment, the beam is on the edge of the ISCT1 refl camera, so not great. There was also very little beam on the REFL WFS, and trying to run the REFL WFS centering servos rails RM2. We are now concerned about the REFL path and possible clipping on the REFL baffle in HAM2 as well.

To finish, Keita turned off the MC2 trans offset, and I reverted the IM3 sliders to the start position. However, the final screenshot here shows the final IM3 position we found where we think we had very little clipping in the input alignment.

None of theae alignments helped us find the beam on ASC POP A, but that's not surprising since we didn't make any IM4 moves. As we finished, Keita set up a long raster of IM3 and IM4 to look for a beam on those QPDs.

 

DAS system, tap testing to calibrate distances along fiber

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. 

I have attached some screenshots which show what the referenced path looks like for the x-arm. Further, it demonstrates how the optical metres of the fibre are now referenced to a certain co-ordinate. With this, we can now correlate any events that we detect to a physical location. In this software, a straight line is drawn between two referenced points. 
In picture 1, the whole arm is shown. 
In picture 2, it is zoomed in on the area around the corner station, showing the limitations in our technique as it is relatively rough considering we know the fibre is curving at this point. 
In picture 3, we see how hovering over the waterfall plot will produce a red point in the refenced fibre showing the location of this channel.