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ID Date Author Type Category Subject
16859   Mon May 16 19:14:17 2022 AnchalUpdateBHDCamera set on AS path and BHDBS output path

[Anchal, Paco, Yuta]

• We aligned AS path avoiding any clipping to the AP table where we setup a camera with a lens.
• To do this we had to move AS6 in North direction for ~1cm.
• The Injection table was imbalanced by this move to drop the IMC transmission to half.
• We did not balance the table again, we steered the input mirror to reach to 1000 counts (out of 1200 nominal) and then used WFS loop to get to the last bit.
• The input to the arm cavities did not change much, XARM was still flashing to 0.8 max height and YARM to 0.2. We recovered these easily using the cavity mirror pair.
• We aligned the LO beam to be spatially matched on BHDBS with AS path.
• The LO beam was steered to roughly overlap with the AS beam outputs on the BHDBS.
• However, the LO beam size is very large and diverges after LO4.
• According to 40m/15379, the 0.15m ROC of LO4 right after the beam waist is supposed to collimate the beam to a 522 um waist.
• We confirmed that LO4 is marked as a 0.15m ROC mirror on its edge and the HR coating is facing the incident beam.
• Conjecture (AG): The coating was applied to the flat side of the optic instead of the curved side.
• This would explain why the beam is continuing to diverge after reflecting from LO4, and diverging fast.
• We need to fix this issue before pumping down otherwise the mode matching would be too poor in BHDBS to have any meaningful results.
• The output of BHDBS was steered out and a GigE camera is set up to see this path.
• The camera is set to see the transmitted AS beam from BHD BS (and reflected LO beam).
• But the camera is unable to see any LO beam due to large divergence.
• The LO beam essentially disappears after ~30 cm from the BHDBS.

16860   Tue May 17 18:43:38 2022 AnchalUpdateBHDPlaced SRM in ITMY Chamber

[Anchal, Paco, Yuta]

### SRM Placement

• SRM was moved from its parked location to the nominal position in the ITMY chamber.
• This imbalanced the table a lot as all SOS towers ended up on the south side of the table.
• I needed additionally three SOS tower side walls to recover the balance of the table.
• I initially tried to use a level meter on my phone which claimed to have 0.1 degrees of accuracy. But it turned out to be a bad idea.
• Eventually, I used the spirit bubble level meter we have, along with the OSEM values of ITMY, AS1, and AS4.
• At the end, the table is balanced as it was before, all SOS are damping usually.

### SRM Sat Amp Box setup

• SRM Gold Box Sat Amp was found near the BS chamber.
• This box was moved to the ITMY chamber.
• The new flange on the East end was marked earlier for SRM. This flange on the vacuum side was connected with new in-vacuum blue ribbon cables.
• We had previously moved the cable post for SRM (40m/16849) behind AS2. This cable post is connected to the old in-vacuum cable.
• It would have changed the table balance to remove this cable post and connect new in-vacuum cables to it, so we decided to do this in the next vent when we put the BHD board on the table.
• For now, we connected the old in-vacuum cable to the new in-vacuum blue ribbon cables inside.
• Note, that the old in-vacuum cable has a gender flipping section which also mirrors the pin layout.
• We installed pin mirroring cables on the outside between the Sat Amp Box and the vacuum flange to revert back the additional mirroring.
• However it happened, now the Sat Amp Box is working, with all OSEMs and coils alive.
• One peculiarity we found was that the SRM face OSEMs have only about 250-300 um of range, which is roughly 3 times less than the other OSEMs in other SOSs.
• SRM side OSEM however behaves normally.
• After installment, at the free-hanging state, SRM LL OSEM is saturated (too bright) and other face OSEMs are close to total brightness state.
• We'll first put the alignment offsets to get the SRM perpendicular to the beam coming from SR2 and then center the OSEMs in this tiny range.
• The low OSEM range could be due to improper biasing from the Sat Amp Box. Hopefully, with new electronics, this issue would go away in future.
16861   Wed May 18 08:30:29 2022 PacoUpdateBHDSRM OpLev

[Paco]

The SRM Oplev injection and detection paths interfere heavily with the POY11. Due to the limited optical access, I suggest we try steering POYM1 YAW and adapting the RFPD path accordingly.

16862   Wed May 18 09:02:52 2022 AnchalUpdateBHDWFS1 PD centered

I centered WFS1 PD so that IMC WFS Servo does not go out of range.

16863   Wed May 18 17:23:15 2022 AnchalUpdateBHDPlaced PRM in BS Chamber

[Anchal, Paco, Yuta, JC]

### SRM Oplev setup

• We setup SRM oplev path for the aligned position of SRM.
• This was bit hard, because the return beam was following almost the same path as the input beam, and the return beam had become about 1 cm in diameter.
• We replaced one of the in-air steering mirror of SRM op-lev input beam with a 1 inch BS on a non-steeerable mount.
• The returning oplev beam is picked at transmission from this BS.
• Note: we are not sure if this BS is actually coated for IR or Visible. We couldn't find a visible BS in the lab. We should order a 2 in diameter visible BS to be placed in this position.
• Half of the input beam would be used for PRM Oplev input.
• The returning beam was focused with a 100mm focal length lens. Again, this lens is not verified to be for visible wavelength. We think it might have an AR coating for IR. We should get a visible lens for this position also.

### PRM Placement

• PRM placed in nominal position + 2 cm, East.
• Currently, PRM SOS tower is blocking BS oplev input beam, this needs to be adjusted.
• Installed PRMOL at nominal position + 2 cm East (to clear path from TT2)
• I balanced the table succesfully, first using spirit bubble level and then OSEM levels of BS, SR2, PR3 and LO2.
• Note, that we need to adjust OSEM positions in many of these SOS before pumping down.
• Input beam from TT2 is going through center of PRM but the reflction is not coming back from PR2, maybe it is missing PR2 or PR2 alignment needs to be adjusted.
16864   Thu May 19 08:51:40 2022 PacoUpdateBHDSRM OpLev

[Paco, Ian]

After agreement from Yuta/Anchal, I moved POYM1 yaw to clear the aforementioned path, and Ian restored the POY11 RFPD path. The demodulation phase might need to be corrected afterwards, before any lockign attempts.

 Quote: [Paco] The SRM Oplev injection and detection paths interfere heavily with the POY11. Due to the limited optical access, I suggest we try steering POYM1 YAW and adapting the RFPD path accordingly.

16865   Thu May 19 18:56:08 2022 yutaUpdateBHDCurrent OSEM sensor values with all the suspensions aligned

Current OSEM sensor values with all the suspensions aligned are attached.
For 'BS','ITMX','ETMX','ITMY','ETMY','PRM','SRM','LO1','LO2', the ones out of the range [200,800] are marked, and for 'PR2','PR3','SR2','AS1','AS4', the ones out of the range [6000,24000] are marked.

16866   Thu May 19 19:05:59 2022 AnchalUpdateBHDBS Chamber all work finished, BHD path setup

[Anchal, Paco, Yuta]

### BS Oplev Path

• The changed position of PRM (40m/16863) meant that BS oplev path is getting clipped by the PRM SOS tower.
• We had to move BSOL ~ 16 cm North and ~ 1.7 cm East.
• This means that the BS Oplev input beam is now coming behind TT2 instead of infront of it.
• We also had to align the beam such that input and returning beam are colinear.
• This meant we, had to change the mount of the upstream beamsplitter in the in-air table so that we can use that for separating the return beam.
• Again, we should order 2 inc visible BS for this path.
• Half of the return beam is making its way all the way back to the laser head. I'm not sure if that can be an issue for our oplev loops.
• We kept the SRM Oplev path same using irises on the table.

### PRM Oplev

• Again, due to changed position of PRM and BS Oplev, it became very hard to setup oplev for PRM.
• We found a special position which allows us to catch returning beam through the center of the window.
• But this returning beam is not prompt reflection from PRM, it is reflection of the HR surface.
• We are hitting about ~5 mm from the edge of PRMOL mirror (because we cannot move the mirror anymore south to avoid clipping BS and SRM input oplev beams)
• We put in a 1.1m focal length lens in the input beam to narrow the beam on PRMOL so that it doesn't clip
• We did not put any lens for the return beam. The sensitivity of this oplev might be low due to slighlty bigger beam on the QPD than others (SRM, BS). We can revisit and insert a lens later if required.

### Interferometer alignment and PRM alignment

• The work on BS table did not change the table balance much. We got back the alignment pretty much instantly.
• We were able to maximize the arm transmissions.
• Then we used a beam card with hole to check for reflection from PRM and used PRM (mostly pitch correction) to get the return beam back in same way.
• This recovered REFL beam on the camera. We used REFLDC signal to align PRM better and maximized it.
• We centered BS, SRM and PRM oplevs after this point.

### LO beam mode correction and spatial overlap

• We tried changing the distance between LO3 and LO4 to get a better output LO beam.
• We also tried to swap the LO4 mirror with the spare mirror but we had the same result.
• Eventually, we decided to move LO3 back to East and LO4 to the west edge of the table. This made the beam sizes comparable.
• Future exercise: We think that LO1 or LO2 might be significantly off-spec in their ROCs which might cause this issue.
• We should rerun the calculations with the ROC values of LO1 and LO2 written in the datasheets and figure out the correct LO3-LO4 length required.
• We can make this change in the next vent if required.
• After the beam sizes were looking approximately similar but more iterations of changing length and realigning are required.

• Push/pull too bright/dark OSEMs in the SOSs (40m/16865).
• Finish LO beam mode correction and spatial overlap.
• Center all oplevs, note all beam positions on camera, and note down all DC PD values at proper alignment.
16867   Fri May 20 12:42:23 2022 TegaUpdateVACDoor installation on the end stations

[JC, Tega, Chub]

Today we installed the 200 lbs doors on the end station chambers.

16868   Fri May 20 20:03:48 2022 PacoUpdateBHDITMY chamber work finished - LO and AS overlapped

[Paco, Anchal, Yuta]

Today, in short we:

• Recovered alignment of arm cavities, PRC (only ITMX aligned), and then altogether with SRM and PRM aligned to maximize all DCPD levels (AS, POP, REFL, TRX, TRY), but SRC was not flashing and the SRM yaw alignment slider was around its max value, so after recording beam positions on cameras Anchal went into the BS chamber and helped steer the SRC alignment using a combination of SRM, SR2 and AS1. After this every beam was nominally aligned except for LO and AS, which remained to be mode matched.
• Mode matched LO3-LO4 by hand --  -- from the ITMY chamber, the final separation between these two mirrors grew by almost 3 inches with respect to the design (!!!) but the LO and AS beams came out nicely. The canonical path used for the steering was LO path, and then we overlapped the beams with the help of a gige basler camera and a couple of DCPDs (Thorlabs).
• Yuta and Paco started running final checks in preparation for Monday (pumpdown). We aligned the IFO, but noted that using Restore/Misalign sometimes results in hysteresis.. so it is not very reliable for fine alignment modes. Then we optimized DC levels, centered all oplevs, and tweaked Green input alignment on XARM and YARM. The XARM was maximized, but in YARM we could still not get high TEM-00 flashing ...
• Unfortunately, we discovered a slight clipping of the GTRY beam through PR3 which could mean the current alignment (pointing) is not hitting PR3 center optimally.
• Attached are the screenshot of current aligned state after the work tonight, with oplevs centered, and the OSEM sensor values.

16869   Mon May 23 13:16:59 2022 PacoUpdateBHDEnd of vent - checks

[Paco, Yuta]

Prep for closing and pump down.

• Aligned IFO to maximize DC levels.
• YARM (flashing peak 0.05 with PRM misaligned), XARM (flashing peak 0.06 with PRM misaligned), PRC (PRY flashing -30 @ POPDC, offset -70 and REFL DC 270), SRC (SRY flashing -30 @ POPDC, offset -70), BHD.
• GTRY clipping
• We tried moving the alignment of PR3, PR2, ETMY, ITMY to reduce clipping and retain IR flashing. We found it kind of difficult, so we only used the unclipped GTRY temporarily to improve the input YAUX injection after which the YAUX locked. We then restored the clipping in favor of the IR beam alignment.
• PR3 position
• PR3 seems to be +1 inch away towards East, nominally placed along North-South, and offset in YAW.
• Aligned OPLEVs to center at around Mon May 23 13:20:32 2022
• Snapshot of all cameras in the control room around Mon May 23 13:24:51 2022

[Chub, JC, Jordan, Yuta, Yehonathan, Paco]

Closed in the following order:

• IMC chamber
• OMC chamber
• BS chamber
• ITMY chamber
• ITMX chamber

[Yuta, Paco]

After closing the heavy doors, we tried to have GTRY less clipped using PR2, PR3, ITMY and ETMY. During this adventure, we also aligned GRY injection beam by hand. Rotating a waveplate for GRY injection made GRY locking stably at GTRY of ~0.3.

16870   Tue May 24 10:37:09 2022 TegaUpdateVACadded FRG channels to slow channel ini file

[Vacuum gauge sensors]

Paco informed me that the FRG sensor EPICS channels are not available on dataviewer, so I added them to slow channels ini file (/opt/rtcds/caltech/c1/chans/daq/C0EDCU.ini). I also commented out the old CC1, CC2, CC3 and CC4 gauges. A service restart is required for them to become available but this cannot be done right now because it would adversely affect the progress of the upgrade work. So this would be done at a later date.

 Quote: git repo - https://git.ligo.org/40m/vac Finally incorporated the FRGs into the main modbusIOC service and everything seems to be working fine. I have also removed the old sensors (CC1,CC2,CC3,CC4,PTP1,IG1) from the serial client list and their corresponding EPICS channels. Furthermore, the interlock service python script has been updated so that all occurrence of old sensors (turns out to be only CC1) were replaced by their corresponding new FRG sensor (FRG1) and a redundnacy was also enacted for P1a where the interlock condition is replicated with P1a being replaced with FRG1 because they both sense the main volume pressure.

16871   Tue May 24 11:04:53 2022 JCUpdateVACBeginning Pumpdown

[JC, Jordan, Paco, Chub]

We began with the pumpdown this morning. We started with the annulus volume and proceeded by using the following:

1. Isolate the RGA Volume by closing of valves VM3 and V7.

2. Opened valves VASE, VASV, VABSSCT, VABS, VABSSCO, VAEV, and VAEE, in that order.

3. Open VA6 to allow P3, FRG3, and PAN to equalize.

4. Turn on RP1 and RP3, rough out annulus volume, once <1 torr turn on TP3. Close V6. Open V5 to pump the annulus volume with TP3.

5. Re route pumping from RP1 and RP3 to the main volume by opening V3 and slowly opening RV1.

6. After ~3.5 hours the pressure in the arms was <500mtorr on both FRG1 and P1a. Turn on TP1 and wait to reach full speed 560 Hz

7. Open V1 with RV2 barely open. The pressure diff between P1a and P2/FRG2 needs to be below 1 torr. This took a couple attempts with the manual valve in different positions. The interlocks were tripped for this reason. Repeat step 7 until the manual gate valve was in a position that throttled pumping enough to maintain the <1 torr differential.

8. Slowly open the manual gate valve over the course of ~ 1 hour. Once the manual gate valve fully opened, pressure in the arms was <1mtorr.

9. V7 was closed, leaving only TP2 to back TP1, while TP3 was used to continue pumping the annuli. Left in that configuration overnight (see attached)

We did have to replace gauge PAN becuase it was reading a signal error. In addition, we found the cable is a bit sketchy and has a sharp bend. The signal comes in and out when the cable is fiddled with.

16872   Tue May 24 15:21:13 2022 AnchalUpdateBHDFreeswing tests of new SOS started

I modified the script freeSwing.py to use damping loop output switches to free the optic instead of watchdog or coil output filters. This ensures that the free swing test is being done at the nominal position of the optic. I started tests for LO1, LO2, As2, As4, PR2, PR3, and SR2 in a tmux session names freeSwing on rossa.

Note: LO2 face OSEMs are hardly sensitive to any motion right now due to excessive pitch offset required for LO beam. We should relieve this offset to LO1 and rerun this test later.

16873   Wed May 25 16:38:27 2022 yutaUpdateSUSSuspensions quick health check

[JC, Yuta]

We did a quick health check of suspesions after the pump down.

Summary:
- ITMX LRSEN is too bright (~761) and not responding to any optic motions (we knew this before the pump down)
- ITMY ULCOIL is not working
- LO1 LLCOIL is not working
- Damping loops need to be retuned, especially for ETMY (too much damping), SRM, PR3 and AS4 (damping too weak)
- MC1 sensor outputs are minus instead of plus
- LO2 OSEMs got stuck during the pump down, but now it is free after some kicks. OSEM sensorr values almost came back (see attached)

What we did:
1. Kicked optics with C1:SUS-{optic}_{UL,LL,UR,LR,SD}COIL_OFFSET one by one with offsets of +/- 10000 (or 100000), and checked if C1:SUS-{optic}_{UL,LL,UR,LR,SD}SEN_OUT16 move in both directions.

2. Check if the optic damps nicely.

3. Attached photo of the note is the result.

16876   Thu May 26 15:55:10 2022 TommyUpdateElectronicsRFSoC Power Spectrum

Finished building power spectrum analyzer for the RFSoC. There are two things that I would like to address down the road. First is that there is an oscillation between positive and negative voltages at the ADC sampling frequency. This creates an undesirable frequency component at the sampling rate. I have not yet figured out the cause of this positive to negative oscillation and have simply removed half of the samples in order to recover the frequency. Therefore, I would like to figure out the root of this oscillation and remove it. Also, we have a decimation factor of 2 as default by the board which we would like to remove but have been unable to do so.

Example: 8 MHz Square Wave from SRL signal generator.

16878   Fri May 27 12:15:30 2022 JCUpdateElectronicsCRT TV / Monitor 6

[Yehonathan, Paco, Yuta, JC]

As we were cleaning up this morning, we heard a high pitch sound that turned into a buzz. After searching for where the sound came from, we noticed the CRT TV went out. We swapped this out with a moniter and used a BNC to VGA adapter to display the cameras.

16879   Fri May 27 15:53:17 2022 TommyUpdateElectronicsRFSoC MTS Work

With some help from the forums, we printed the status of the DAC MTS sync and were able to determined that our board's vivado design does not have MTS enabled on each tile. To fix this, we will need to construct a new Vivado desgin for the board. We were also warned to "make sure to generate correctly a PL_clock and a PL_sysref with your on board clock synthesizers and to capture them in the logic according to the requirements in PG269" of the RF Manual. From this we should be able to sync the DAC and ADC tiles as desired.

 Quote: We followed the manual's guide for setting up MTS to sync on external signal. In the xrfdc package, we update the RFdc class to have RunMTS, SysRefEnable, and SysRefDisable functions as prescribed on page 180 of the manual. Then, we attempted to run the new functions in the notebook and read the DAC signal outputs on an oscilloscope. The DACs were not synced. We were also unable to get FIFOlatency readings.

16882   Tue May 31 14:44:02 2022 JCUpdateElectronicsCRT TV / Monitor 6

[Paco, JC]

Paco and I fixed the ethernet cable which was hanging. We stopped models c1x07 and c1su2, realigned the cable to follow the shelf from top, and returned to turn on the computers.

Note: There was not a long enough ethernet cable, so we used a female to female adapter and attached 2 ethernet cables.

 Quote: [Yehonathan, Paco, Yuta, JC] As we were cleaning up this morning, we heard a high pitch sound that turned into a buzz. After searching for where the sound came from, we noticed the CRT TV went out. We swapped this out with a moniter and used a BNC to VGA adapter to display the cameras.

16883   Tue May 31 17:30:01 2022 YehonathanUpdateBHDGreen shutters fixed

[Paco, Yehonathan]

We fixed the slow control over the green beam shutters.

At the Y arm the wrong BNC was connected to the shutter driver. We connected the correct BNC to the driver and switched the remote mode. The green Y shutter now works but in reverese, meaning that sending 1 to C1:AUX-GREEN_Y_Shutter closes the shutter and vice versa. This needs to be fixed.

At the X end the problem was a bit more complicated. Previously, the shutter was controlled by c1auxey. We figured that c1auxex has a lot of spare bio channels. We found an Acromag BNC front panel (with wires already soldered to the BNCs) lying around in the lab and installed it on the c1auxex Acromag chassie. We then connected the topmost BNC to channel 0 on XT1111A in the chassie. The BNC was connected to the green shutter driver on the X end.

EPIC channel was added to the c1auxex db file while it was commented out on the psl shutters db file. Modbus was restarted on c1auxex and c1psl. c1psl had to be burt restored to regain MC lock. Now the green X shutter works properly.

16884   Wed Jun 1 11:56:28 2022 yutaUpdateALSShutter driver for GRY replaced

[JC, Yuta]

We replaced a shutter driver for GRY since it stopped working this morning.
We replaced it with a free driver which was sitting on the ITMY table.
The reverse polarity issue of C1:AUX-GREEN_Y_Shutter was fixed by switching one of the switches of the driver from N.O. to N.C.

Also, "Toggle" button was added to IFO_ALIGN.adl so that we can toggle shutters easily to find TEM00. It runs /home/controls/Git/40m/scripts/ALS/ShutterToggler.py.

 Quote: The green Y shutter now works but in reverese, meaning that sending 1 to C1:AUX-GREEN_Y_Shutter closes the shutter and vice versa. This needs to be fixed.

16888   Fri Jun 3 15:22:51 2022 yutaUpdateLSCBoth arms locked with POY/POX, IR beam centered on TMs with ASS

[JC, Paco, Yuta]

We locked both Y and X arms with POY11 and POX11.
RFM fix (40m/16887) enabled us to use triggering using C1:LSC-TRY/X_OUT.
IR beam is now centered on TMs using ASS (for Yarm, ASS loops cannot be closed fully, so did it manually).

What we did:
- Aligned both arms so that the beams are roughly centered at TMs using cameras.
- Yarm lock was easy, but Xarm lock required gain tuning. Somehow, Xarm required x3 higher gain as follows, although the amplitude of POX11_I_ERR seems to be almost the same as POY11_I_ERR. I suspect it is something to do with power normalization matrix (TRX flashing is almost a double of TRY flashing).

C1:LSC-YARM_GAIN = 0.01
C1:LSC-XARM_GAIN = 0.03

- Run ASS for Yarm. ASS loops cannot be closed fully using default feedback parameters. I guess this is because ITMY ULCOIL is not working (40m/16873). ASS demodulated signals were manually zero-ed by manually aligning ETMY, ITMY and PR3 (and some TT1 and TT2), except for demodulated signals related to ITMY. Beam on ITMY was centered just by using our eyes.
- Run ASS for Xarm. It seemed to work well.
- After this, TRX and TRY were as follows and beam positions on TMs were as attached.

C1:LSC-TRX_OUT ~0.95
C1:LSC-TRY_OUT ~ 0.58

(TRX is somehow lower than what we had yesterday... 40m/16886; TRX and TRY photodiode alignment was checked, but seems to be OK.)

- Centered TMs and BS oplevs.

Next:
- POX and POY demodulation phases are not fully optimized. Needs re-tuning.
- Tweak GRX and GRY injection (restore GRY PZTs?)
- Install ETMXT camera (if it is easy)
- MICH locking
- RTS model for BHD needs to be updated

16889   Fri Jun 3 17:42:50 2022 yutaUpdateLSCMICH locks with AS55_Q

AS path at AP table as re-aligned and confirmed that MICH can be locked with AS55 Q.

What we did:
- Aligned AS55 and AS110 paths at AP table. AS55 was not receiving enough light. AS110 was not receiving light at all.
- Changed AS55 I and Q whitening gain from 3dB to 42dB.
- Zero-ed the RF offsets manually. C1:LSC-AS55_Q_IN1 is having too large offset. When PSL shutter was closed, it reads 13950! Needs investigation.
- Locked MICH with PRM mis-aligned with configurations attached.

Other Issues:
- C1:IOO-MC_TRANS_SUM is now stuck at 14009. MC auto locker doesn't work correctly. FIX ME!

16890   Sun Jun 5 19:46:40 2022 PacoUpdateLSCFixed IMC Trans sum issue

[Paco]

Fixed the issue below:

 Quote: Other Issues:  - C1:IOO-MC_TRANS_SUM is now stuck at 14009. MC auto locker doesn't work correctly. FIX ME!

by noting that the C1:IOO-MC_TRANS_SUMFILT_OUT was being held to 14009 counts for some reason. Disabling hold quickly let the IMC autolocker act back.

WFS were also turned ON, and there were a couple other control outputs being held on that loop... Strange!

16891   Mon Jun 6 09:37:16 2022 JCUpdateSUSInMatCalc

[Paco, JC]

Paco and I attempted to calculate the input matrices from May 24, 2022, but the OSEM data was all saturated and not very useful. Therefore, we decided to manually investigate the appropriate coil offsets for all BHD SUS. Before, the default offset kick was 30000 counts, but we found that LO1, AS1, AS4, and PR2 cannot take more than 5000 counts. As for LO2, SR2, and PR3 cannot take more than 2000 counts before saturating. Note that all these kick test were taken by kicking OSEM UL on all BHD Optics.

We started the freeSwing.py script on tmux freeSwing session for tomorrow at 1:00 am for only the 5000 count offset SUS.

16892   Mon Jun 6 13:35:11 2022 PacoUpdateLSCFirst calibrated spectra of MICH at AS55 Q

[Paco, Yuta]

On the topic of high AS55_Q RFPD offset, it seems it stems from a small residual offset on top of the 42 dB whitening filter gain (previously 3 dB). We verified this by looking in the past using dtt and seeing an offset of ~ 100 counts, which are consistent with the hotfix. We reverted the whitening filter gain to +24 dB, in order to accomodate the 10% power difference from AS2. We decided to move forward, and try locking MICH using AS55_Q_ERR. The IQ mixing angle was changed to -167 deg from -122 deg to minimize the signal in AS55_I_ERR. We have also added comb60 filters for AS55. The LSC_MICH filter gain was adjusted to -6 (used to be -13 in the configuration script) to get a MICH_OLTF UGF of 90 Hz (which is the previously measured value as of 2021 July), see Attachment #1 for the MICH OLTF estimate.

We then calibrate MICH using the fringe amplitude, so that  $4 \pi I_{0} / \lambda = 1.299 \times 10^9 {\rm cts / m}$, where $I_{0}$ is the amplitude of the error point (C1:LSC-AS55_Q_ERR_DQ) in our case ~ 110 +- 2 counts. The calibrated error point spectral density is shown in Attachment #2. Calibration is done into meters in terms of difference between BS to ITMX length and BS to ITMY length.

16894   Mon Jun 6 21:01:22 2022 yutaUpdateIMCMC1 OSEM sensor sign flipped, MC1/2/3 free swinging overnight for inmat diagonalization

[Tomislav Andric, Rana, Yuta]

We put -1 to MC1 OSEM sensor gains and re-tuned MC1 damping.
We also kicked MC1, MC2, MC3 tonight for input matrix diagonalization.

MC1 damping investigations:
We put -1 to MC1 OSEM sensor gains so that UL/UR/LR/LL/SDSEN_OUT will be positive like other optics.
OSEM damping filter gains were adjusted.
We have also checked if having +1 for all UL/UR/LR/LL/SDCOIL_GAIN is correct or not. It has been like this at least for the past year.
It should be -1 for UR and LL to account for magnets, but if we did put -1 or them, kick in C1:SUS-MC1_PIT_OFFSET mostly gave yaw kick and kick in C1:SUS-MC1_YAW_OFFSET mostly give pitch kick.
So, we reverted them to be +1.

Input matrix diagonalization:
We also kicked MC1, MC2, MC3 tonight input matrix diagonalization.
Kick was done manually at the following times local.
- MC1 20:08 June 6th, 2022
- MC2 20:24 June 6th, 2022
- MC3 20:21 June 6th, 2022
We will leave watchdogs shutdown to free swing overnight (damping loops are "on").
This will help get better angular sensor from OSEMs to calibrate WFS signals.

Next:
- Investigate why MC1 coils gains have +1 for all
- Calculate input matrix. Make sure SUSPOS/PIT/YAW/SIDE_IN will be in the units of um or urad.

Suggestions:
- Add filter ramp time of 1sec for all by default
- Make null stream channel from input matrix for diagnostics

16895   Mon Jun 6 22:08:55 2022 KojiUpdateIMCMC1 OSEM sensor sign flipped, MC1/2/3 free swinging overnight for inmat diagonalization

Note that MC1 has a new style sat amp because the old one collapsed. The sign flip might have been the result of the replacement

16896   Tue Jun 7 17:26:21 2022 yutaUpdateSUSITMY ULCOIL mystery not solved

[Paco, Yuta]

We investigated the ITMY ULCOIL issue (40m/16873).
ULSEN is sensing the optic motion but ULCOIL cannot move the optic.
We confirmed that the coil input is there upto satellite amplifier output.
We also checked that ULCOIL have 3.3 mH and 16 Ohms, which are consistent with other coils.
Mystery remains...
We need to investigate ITMY ULCOIL in the next vent.

What we did:
- Checked again that C1:SUS-ITMY_ULCOIL_OFFSET does not kick ITMY using OSEM sensor signals and oplev signals. ULSEN moves when ITMY is kicked by other coils.
- Checked that kick gives voltage changes at coil driver and satellite amplifier output. We unplugged J1 DB25 cable from the feedthru flange and checked the signals sent to coil with oscilloscope.
- Measured inductance (using BK PRECISION LCR meter) and resistance (using Fluke) of coils for ITMY. Below is the result. UL coil seems to be consistent with other coils. (It seems like BK PRECISION one wil give wrong resistance if the dial is set to the resistance value which is too low compared with the one you want to measure. If you want to measure 16Ω, set the dial to larger than 20Ω, not 2Ω)

Feedthru connector: ITMY1 Pin 3-15 / R = 16.3Ω / L = 3.32 mH (UL) Pin 7-19 / R = 16.4Ω / L = 3.30 mH (UR) Pin11-23 / R = 16.2Ω / L = 3.31 mH (LL)

Feedthru connector: ITMY2 Pin 3-15 / N/A Pin 7-19 / R = 16.3Ω / L = 3.30 mH (SD) Pin11-23 / R = 16.4Ω / L = 3.33 mH (LR)

Discussions:
- UL is the only short OSEM in ITMY OSEMs.
- ITMY have dumbells for magnets.
- If UL magnet is off, ULSEN would not work. Something not magnetic is working for shadow sensing for UL? Dumbells?
- ULSEN just sensing some coupling from other OSEMs?

16897   Tue Jun 7 18:32:46 2022 DeekshaUpdateElectronicsNoise Budgeting ADC (of redpitaya)

Made plots on i/p noise of redpitaya . Need to reconsider sampling frequency (to improve plot at lower freq)

16898   Tue Jun 7 19:13:12 2022 yutaUpdateSUSAgreement on suspension damping loop polarity conventions

Anchal, Paco and I agreed to follow the polarity conventions below for suspension damping loops.
Some of the polarity/gains were changed to homogenize all the suspensions to the convention.
All the suspensions are homogenized except for MC1 (which have all - in sensor inputs and all - in coil outputs) and AS1 (SDCOIL_GAIN have the same sign as LL).

*SEN_GAIN to be +1
INMATRIX to be the following, and calibrated so that SUSPOS/SIDE_IN will be um and SUSPIT/YAW_IN1 will be urad (calibration to be done later)
+ + + + *
+ + - - *
+ - - + *
* * * * +
SUS*_GAINS to be +

TO_COIL gains to be the following
+1 +1 +1  *
+1 +1 -1  *
+1 -1 +1  *
+1 -1 -1  *
*  *  * +4
*COIL_GAIN to be the following or flipped one so that SUS*_GAINS will be +
+
-
+
-
+

To do this, the following changes were made

For BS, ITMX, ITMY, PRM, SRM, ETMX, ETMY, MC1, MC2 and MC3 ("old" suspensions), TO_COIL_5_4_GAIN (for side) is changed from +1 to +4 and SUSSIDE_GAINs are divided by 4 accordingly.
For ETMX, the sign of SUSSIDE_GAIN is flipped to +, and SDCOIL_GAIN to be -1 (it was +1).
For MC1, *SEN_GAINs are - (not following the convension; see 40m/16894). The sign of INMATRIX_4_5 (for side) is flipped to +, SUSPOS/PIT/YAW_GAIN are flipped to +, and *COIL_GAIN are flipped to - (not following the convension). IMC WFS output matrix components for MC1 were also flipped.

16899   Tue Jun 7 19:40:45 2022 AnchalUpdateSUSITMY changed output matrix to disable use of UL coil

Since UL coil actuation is lost, we modified the output matrix of ITMY to use only UR, LR and LL face coils for POS, PIT and YAW actuation. The output matrix was changed to following:

 POS PIT YAW SIDE UL 0 0 0 0 UR 1 1 0 0 LL 1 0 1 0 LR 0 -1 -1 0 SIDE 0 0 0 1

After this change, the damping was still working as good as before. I took PIT to POS/PIT/YAW and YAW to POS/PIT/YAW coupling measurements by exciting C1:SUS-ITMY_ASCPIT[YAW]_EXC and seeing effect at C1:SUS-ITMY_SUS[POS/PIT/YAW]_IN1 when the damping loops were off. Attached are the results. We were able to reduce PIT to YAW and YAW to PIT coupling by 10 dB by this simple change in output matrix. More coil balancing or off-diagonal termsmight help more and should be attempted if required. The coupling to POS did not change much.

Note that attachment 1 shows transfer functions from excitation point to the DOF sensing inputs while attachment two looks at ratio of C1:SUS-ITMY_SUS[POS/PIT]_IN1 to C1:SUS-ITMY_SUSYAW_IN1 which is the actual quantity of interest. I didn't repeat the PIT measurement due to lack of time.

Also note that all such measurements are being recorded in our new measurements git repo. We'll populate this repo with diaggui template+data files as we do measurements.

16900   Wed Jun 8 16:03:12 2022 KojiUpdateVACPower Outage 220608: Vacuum Recovery

=== Observation ===

• TP1/2/3 failed. AUX RP did not survive the power outage (of course)

=== Initial Recovery of TP2/TP3 ===

• Stopped TP1/2/3
• Restored RP AUX at the wall breaker module
• Restarted TP2/3

=== Rough pumping down ===

• Found RP1/RP3 left connected (unusual)
• Turned on RP1 and RP3
• Opened V6 and V7 for roughing of the pump spool. Now 0.3 torr for P2/P3/PA* (annuli) - ready to open V4 and V5 to backup TP1 by TP2 and TP3. Waiting for TP2/3 to be accelerated

=== Towards main volume pumping ===

• TP2 accelerated and opened V4 (This caused V6 to close). RP1 and RP3 stopped.
• TP3 hasitated to spin up. Stopped for now.
• TP1 needed to be reset to clear the displacement errors. Once the errors were cleared, TP1 was restarted (acclerating).
• TP1 at normal speed. Opened V1 (main volume pumping started)

• Disconnected RP1/RP3 line.

• TP3 was restarted and is now stable at 55k RPM (indicated as soft spin / low speed). Pushed "Stand By On" and "then "Stand By OFF". This makes the TP3 back to "NORMAL". Switched to "Stand By On".
• TP2 was also switched to "Stand By On".

Now the main volume and the annuli are pumped down TP1 and TP2/TP3 with RP AUX backing.

The attachment is the pressure glitch for the main volume.

16901   Wed Jun 8 16:33:26 2022 KojiUpdateGeneralPower Outage 220608: HVAC restored

I found the HVACs for the ends were off. They were turned back on.

16902   Wed Jun 8 16:57:46 2022 KojiUpdateIOOPower Outage 220608: IMC restored

The IMC alignment was restored and the IMC is nicely locking.

Once the vacuum level recovered P<1e-4 torr, the PSL shutter was able to be opened.

The IMC was still flashing, so the lock to TEM00 was possible.

Once it was locked, the MC2 alignment was tweaked and the autolocker and the WFS kicked in to help the locking/alignment.

The transmission is ~13k and seems reasonable considering the low PMC transmission of the PMC (0.672)

16903   Wed Jun 8 18:16:20 2022 yutaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

To see if the ULCOIL channel of the ITMY coil driver is working or not, I swapped ITMY coil driver and ITMX coil driver by swapping DB15 cable (see Attachment #2).

With this swap, I confirmed that ITMX can be kicked with C1:SUS-ITMY_ULCOIL_OFFSET, but ITMY cannot be kicked with C1:SUS-ITMX_ULCOIL_OFFSET (see Attachment #1).

This means that the issue is not the in-air electronics.
Mystery remains again...
We need to investigate ITMY ULCOIL in the next vent.

I revereted the swap and confirmed that damping loops work fine again.

16904   Thu Jun 9 23:08:39 2022 ranaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

what was the result of the inductance measurement? should be ~3.3 mH as measured from the flannge or cable that goes to the flange from sat amp.

16905   Fri Jun 10 13:02:14 2022 yutaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

ITMY ULCOIL was measured to have ~3.3 mH as measured from the flange. RTFE 40m/16896 .

 Quote: what was the result of the inductance measurement? should be ~3.3 mH as measured from the flannge or cable that goes to the flange from sat amp.

16906   Fri Jun 10 13:52:22 2022 JCUpdateOPLEV TablesITMX, ITMY, and Vertex Table Beam Paths

I have at taken photos and added arrows which signify the beam paths for ITMX, ITMY, and Vertex Oplev tables.

16907   Fri Jun 10 15:02:04 2022 yutaUpdateSUSServo gain sign flipped for MC1 WFS relief

The servo gain for MC1 in /opt/rtcds/caltech/c1/Git/40m/scripts/MC/WFS/reliefWFS was flipped to account for COIL_GAIN flip done in 40m/16898.
The reliefWFS script now works fine.

ezcaservo -r 'C1:SUS-MC2_ASCPIT_OUT16' -g ${g} -t${ts} C1:SUS-MC2_PIT_COMM &
ezcaservo -r 'C1:SUS-MC2_ASCYAW_OUT16' -g ${g} -t${ts} C1:SUS-MC2_YAW_COMM &
ezcaservo -r 'C1:SUS-MC1_ASCPIT_OUT16' -g -${g} -t${ts} C1:SUS-MC1_PIT_COMM &
ezcaservo -r 'C1:SUS-MC1_ASCYAW_OUT16' -g -${g} -t${ts} C1:SUS-MC1_YAW_COMM &
ezcaservo -r 'C1:SUS-MC3_ASCPIT_OUT16' -g ${g} -t${ts} C1:SUS-MC3_PIT_COMM &
ezcaservo -r 'C1:SUS-MC3_ASCYAW_OUT16' -g ${g} -t${ts} C1:SUS-MC3_YAW_COMM &

16908   Fri Jun 10 15:04:23 2022 ranaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

Its good that the inductance test passed. This means that the coil is OK. How does the inspection photo look? This is the one you guys took of the ITM OSEM that shows the position of the magnet w.r.t. the coil. Also, how does the free swinging spectra look? Either one of these might indicate a broken magnet, or a sticky EQ stop.

16909   Fri Jun 10 20:11:46 2022 yutaUpdateASCYarm ASS re-tuning in progress

[Anchal, Yuta]

We tried to re-tune Yarm ASS today. It cannot be fully closed as of now. I think we need to play with signs.

Motivation:
- We want to make sure Yarm ASS work with current ITMY coil matrix (40m/16899).
- ASS makes the beam positions on test masses to be the same every day.

What we did:
- Adjusted A2L paths of C1:ASS-YARM_OUT_MTRX based on cavity geometry. For the paths to maximize the transmission using TT1 and TT2, we just assumed they are correctly calculated by someone in the past.
- Adjusted OSC_CLKGAINs so that ITMY and ETMY will be shaken in the same amplitude in terms of radians. The ratio of the excitation was determined to take into account for the oscillator frequency difference between DOFs.
- Checked the time constant of A2L paths by turning on A2L paths only, and checked that of max-transmission paths by turining on them only.
- Adjusted DEMOD_SIG_GAINs so that their time constants will be roughly the same, with C1:ASS-YARM_SEN_MTRX fully identity matrix and all servo GAINs to be +1.
- Re-tuned DEMOD_PHASEs to minimize Q signal. C1:ASS-YARM_ITM_PIT_L_DEMOD_PHASE and C1:ASS-YARM_ITM_YAW_T_DEMOD_PHASE were re-tuned within +/- 5 deg.
- These changes are recorded in /opt/rtcds/caltech/c1/Git/40m/scripts/ASS/ASS_DITHER_ON.snap now.

Result:
- A2L loops seems to be working, but max-transmission paths seems to diverge at some point. I think we need to play with the signs/gains of max-transmission paths for C1:ASS-YARM_OUT_MTRX.
- Attached is the current configuration we achieved so far.

16910   Fri Jun 10 21:10:01 2022 yutaUpdateSUSITMY ULCOIL mystery: Coil driver swap test

We checked the photos we have, but we didn't have the photos which show ULCOIL situation clearly.

Free swing of ITMY (and others) will be done this weekend to see the OSEM spectra and resonant frequencies.

16911   Mon Jun 13 20:26:09 2022 yutaUpdateASCYarm ASS re-tuning in progress -part 2-

[Anchal, Yuta]

We are still in the progress of re-commissioning Yarm ASS.
Today, we tried to adjust output matrix by measuring the sensing matrix at DC.
Turning on yaw loops kind of works, but pitch does not. It seems like there is too much coupling in pitch to yaw.
We might need to adjust the coil output matrix of ITMY and ETMY to go further, and/or try measuring the sensing matrix including pitch - yaw coupling.

What we did:
- Confirmed that turning on TT1 and TT2 loops (max-transmission loops) work fine. When we intentionally misalign TT1/2, the ASS loops correct it. So, we moved on to measure the sensing matrix of A2L paths, instead of using theoretical matrix caluclated from cavity geometry we used last week (40m/16909).
- Instead of +/-1's, we put +/-2's in the ITMY coil output matrix to balance the actuation between ETMY and ITMY to take into account that ITMY is now using only two coils for actuating pitch and yaw (40m/16899).
- Measured the change in C1:ASS-YARM_(E|I)TM_(PIT|YAW)_L_DEMOD_I_OUT16 error signals when offset was added to C1:SUS-(E|I)TMY_ASC(PIT|YAW)_OFFSET. We assumed pitch-yaw coupling is small enough here. Below was the result.

                            ETM PIT error  ITM PIT error ETM PIT OFFSET of +100cnts: -3.0cnts       -2.99cnts ITM PIT OFFSET of +100cnts: -11.94cnts      -5.38cnts

                            ETM PIT error  ITM PIT error ETM YAW OFFSET of +100cnts: -3.42cnts      -16.93cnts
ITM YAW OFFSET of +10 cnts: +1.41cnts      +0.543cnts

- Inverted the matrix to get A2L part of C1:ASS-YARM_OUT_MTRX. Attachment #1 is the current configuration so far.
- With this, we could close all yaw loops when pitch loops were not on. But vise versa didn't work.
- Anyway, we aligned the IFO by centering the beams on test masses by our eyes and centered all the oplevs (Attachment #2).

Next:
- Do coil balancing to reduce pitch-yaw coupling
- Measure sensing matrix also for pitch-yaw coupling
- Xarm ASS is also not working now. We need to do similar steps also for Xarm

16912   Tue Jun 14 08:41:36 2022 JCUpdateOPLEV TablesBS Oplev Table Sketch

[JC]

Lately, I have been working on a 3d sketch of the BS OPLEV Table on SolidWorks. This is my progress so far, a few of the components I will have to sketch myself, such as the HeNe laser and photodiodes. This will just be a general layout of the HeNe laser, optics, and photodiodes.

16913   Tue Jun 14 18:45:43 2022 AnchalUpdateSUSLO2 lower magnets are stuck in coil, won't come off

[Anchal, Yuta]

In the weekend, I ran a free swing test on all optics. During this test, LO2 magnets got stuck to the coil because LO2 PIT alignment was very high, making its lower OSEMs almost fully dark and upper OSEMs almost fully bright. Today we realized that LO2 is actually stuck and is not coming off even when we dither PIT alignment. We tried several ways but could not get this off.

Do we have any other method to get magnets off in vaccum?

It will be pretty bad if we try anything related to BHD with LO beam reflecting off a stuck mirror. Does anyone have any suggestions other than venting and fixing the issue?

16914   Tue Jun 14 19:34:06 2022 yutaUpdateSUSResonant frequency identification from the free swing test

[JC, Anchal, Yuta]

We are working on resonant frequency idendification from the free swing test done last weekend.
Table below is the resonant frequencies identified, and attached are the plots of peak identification for some of our new suspensions.
To identify the resonant frequencies, the kicks were done in each degrees of freedom so that we can assume, for example, SUSPOS will be mostly excited when kicked in POS and the heighest peak is at the POS resonant frequency.
For PR3, AS1 and ETMY, the resonant frequency idendification needs to be done in the order of POS, PIT, YAW, SIDE and identified frequencies need to be removed when finding a peak.
Other than that, the identification was done without any prior assumptions on the suspensions.
For ITMY, ETMY, PR2, PR3, AS1, AS4, yaw has lower resonant frequencies than pitch, as opposed to other suspensions.
For LO1, POS and PIT frequencies might be swapped because LLCOIL is not working (40m/16898) and POS/PIT kicks both might be excited SUSPOS/PIT.
LO1 coil output matrix was temporarily modified so that we use only two coils for POS/PIT/YAW excitation (Attachment #7), as we did for ITMY (40m/16899).

The scripts for the free swinging test and analysis live in /Git/40m/scripts/SUS/InMatCalc

     POS    PIT    YAW    SIDE
BS   0.990  0.748  0.794  0.959
ITMY 0.987  0.739  0.634  0.948 fPIT > fYAW
ETMY 0.979  0.816  0.649  0.954 fPIT > fYAW
ITMX 0.978  0.586  0.758  0.959
ETMX 0.962  0.725  0.847  1.000
PRM  0.939  0.541  0.742  0.990
PR3  1.019  0.885  0.751  0.989 fPIT > fYAW
PR2  0.996  0.816  0.724  0.999 fPIT > fYAW
SRM  0.969  0.533  0.815  0.985
SR2  0.978  0.720  0.776  0.997
LO1  0.926  1.011  0.669  0.993 POS AND PIT MIGHT BE SWAPPED
LO2  0.964  0.998  0.995  0.990 WRONG DUE TO STUCK (40m/16913)
AS1  1.028  0.832  0.668  0.988 fPIT > fYAW
AS4  1.015  0.800  0.659  0.991 fPIT > fYAW
MC1  0.967  0.678  0.797  0.995
MC2  0.968  0.748  0.815  0.990
MC3  0.978  0.770  0.841  0.969

16915   Tue Jun 14 20:57:15 2022 AnchalUpdateASCYarm ASS working now

I finally got YARM AS to work today. It is hard to describe what worked, I did a lot of monkey business and some dirty offset measurements to create the ASS output matrix that gave results. Note that I still had to leave out ITMY PIT L error signal, but transmission was maximizing without it. The beam does not center fully on ITMY in Pit direction right now, but we'll mvoe on from this problem for now. Future people are welcome to try to make it work for this last remaining error signal as well.

commit

16916   Wed Jun 15 07:26:35 2022 JCUpdateVACBeginning Pumpdown

[Jordan, JC]

Jordan and I went in to retore the Vacuum System back to it's original state before the power loss on June 8, 2022. The process went smoothly as we first closed V7 and opened VM3 (in that order).

The RP1/3 line did not have the KF blank installed. That was added and the RP flex line was capped off.

 Quote: [JC, Jordan, Paco, Chub] We began with the pumpdown this morning. We started with the annulus volume and proceeded by using the following: 1. Isolate the RGA Volume by closing of valves VM3 and V7. 2. Opened valves VASE, VASV, VABSSCT, VABS, VABSSCO, VAEV, and VAEE, in that order. 3. Open VA6 to allow P3, FRG3, and PAN to equalize. 4. Turn on RP1 and RP3, rough out annulus volume, once <1 torr turn on TP3. Close V6. Open V5 to pump the annulus volume with TP3. 5. Re route pumping from RP1 and RP3 to the main volume by opening V3 and slowly opening RV1. 6. After ~3.5 hours the pressure in the arms was <500mtorr on both FRG1 and P1a. Turn on TP1 and wait to reach full speed 560 Hz 7. Open V1 with RV2 barely open. The pressure diff between P1a and P2/FRG2 needs to be below 1 torr. This took a couple attempts with the manual valve in different positions. The interlocks were tripped for this reason. Repeat step 7 until the manual gate valve was in a position that throttled pumping enough to maintain the <1 torr differential. 8. Slowly open the manual gate valve over the course of ~ 1 hour. Once the manual gate valve fully opened, pressure in the arms was <1mtorr. 9. V7 was closed, leaving only TP2 to back TP1, while TP3 was used to continue pumping the annuli. Left in that configuration overnight (see attached)   We did have to replace gauge PAN becuase it was reading a signal error. In addition, we found the cable is a bit sketchy and has a sharp bend. The signal comes in and out when the cable is fiddled with.

16917   Wed Jun 15 15:03:41 2022 KojiUpdatePSLPMC input beam aligned

The commissioners complained about the PMC alignment. The PMC input beam was aligned. It made the transmission improved from 0.72 to 0.74.

FYI: Which steering mirrors do we use for the PMC beam alignment?
The mounts are indicated with the red arrows in Attachment 2.
You have to move these two in common and differential for each pitch and yaw.
The first steering (the right one in the picture) has the beam going through the immediate back of the mount.
So touching the yaw knob of this mount needs some care so that you don't block the PMC refl beam.

ELOG V3.1.3-