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Section: H1
Task: PSL
Just to confirm that there's nothing grossly wrong with the beam coming into PSL ISS 2nd loop array, I tried to minimize the jitter coupling from IM3 dither to PDSUM_INNER. If there is something terrible, we might have to change the IM2 and IM3 angle again, which will change the input alignment into the IFO, so it makes sense to say that IM2/IM3 are good now. That way, ISS alignment will be truly isolated from the IFO.
I moved two picos for ISS and ended up with the following coupling in RIN/m:
This looks to be consistent with October/2025 measurements in the lab: https://dcc.ligo.org/T2500077-v4, the screenshot of which is attached here as 2025October_T2500077.png. INNER (i.e. PD1/2/3/4) PIT is somewhat worse, INNER_YAW is at least a factor of 3 better. (OUTER_PIT is somewhat better and OUTER_YAW is a factor of 2 worse, but I haven't tried to make OUTER sensor better.)
I went away from the center of the QPD: PIT=-0.603 YAW=-0.295, which corresponds to -84um in PIT and -41um in YAW. This is to say that the displacement is not huge at all. Don't try to center.
The first pico (ch1 for HAM2) was moved from (X,Y)=(0,0) to (569,-476), the second (ch8) from (0,0) to (685, -541).
Though individual diode outputs are all different from O4 days because of different alignment, PDSUMINNER and PDSUMOUTER are the same as in O4 (compare ISSpath_align_20260817.png with ISS_INNER_and_OUTER_in_O4.png).
I didn't make a huge scan so I don't know how far the beam is from the edge of the diodes, but this already looks OK to me. If needed we can search for a better spot position further without changing IM2/3.
What was done:
DTT template and my detailed memo of what was done are available in /ligo/home/keita.kawabe/ISS2ndAnd3rdLoop/ISS2ndLoopAlignment
FAMIS 63911
PMC REFL has been rising very slightly, but otherwise, no major events of note.
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.
FAMIS 63910
Last Tuesday's interlock work and brief time in the enclosure are clearly seen on many trends, and essentially everything came back as expected. One item of note is the PMC, which relocked at a slightly higher temperature, which seems to have caused the transmitted power to be a bit lower while the reflected power is a bit higher.
The PSL is now back on after the CDS and interlock work over the last couple of days. We turned the PSL back on yesterday and locked the PMC at the end of the day so both could warm up overnight. This morning I tweaked beam alignment into both the PMC and RefCav. With the ISS ON, PMC Trans is ~104.8 W and PMC Refl is ~28.6 W, while the FSS RefCav TPD is ~0.527 V. PMC Trans and Refl have not quite returned to their pre-interlock work levels, but in the past we've seen that it can take up to 24 hours for this to occur. To that end, I have left the ISS OFF while the PMC continues to warm up, but it can be turned on whenever it is needed.
[Matt, Jason O, Maik F (remote)]
We wanted to see the run hours on the PSL systems at both sites to check on the health of everything (and as an easy kickoff on the FCA review of the detector itself....see slide 10 of G2610464). The chillers we swap out regularly to get refurbished so we have no concerns there, but the PSL laser diode lifetimes are the point of interest here.
LLO
LLO finished the O4 upgrade of the PSL circa November 2022.
LLO appear in very good shape. The run hours LLO have are:
AMP1: 30,427 hours
AMP2: 30,399 hours
From Maik "The diodes have the standard specifications of 20,000h but the vendor typically says that they will do more than 30,000h which you proved !"!
The diode currents for the laser diodes at LLO has not been changed from its initial set points at install.
Note: The laser diode current has to be changed as the laser diodes start to die to maintain the same output power from the diode itself and retain the thermal lens profile of the crystals inside the amplifier.
LHO
LHO finished their O4 upgrade of the PSL circa February 2022.
LHO are in a bit more of a concerning shape than LLO. The run hours LHO have are:
Amp1: 38,512
Amp2: 38,365
More concerningly from LHO's point of view, LHO HAVE had to start adjusting their laser diode currents to maintain output form their laser diodes. From Jason "We’ve been able to keep output power good by increasing the injection currents, but our PMC reflected power has more than doubled since install (~12 W -> ~28 W). I can’t get it lower with injection current increases, further increases only increase PMC Refl; at this point we’d have to redo the mode matching to the PMC to restore our original power available to the IFO"
Summary
Both sites laser diodes are beyond the manufacturers specifications for runtime.
LHO have around a year of extra runtime on their laser diodes and the LHO diodes have started to degrade in terms of performance.
Each site does have a complete set of spare diode boxes that can be swapped in. LLO's have hours on them as they are part of the T&T lab setup, but LHO's should still be brand new (other than burn in time). However we do need to starting thinking/planning about refurbishing (or buying new), laser diodes for the PSL system. So at this point in time both sites should be fine for the IR1 run (however laser diodes typically degrade at a non-linear rate and so LHO will have to keep an eye on their performance and make a judgment call on if they think they need to swap theirs at some stage). However for O5 (or even the upgrades/commissioning before them), both sites are going to have to swap out to fresh laser diodes.
FAMIS 63909
Ignoring the past couple of hours when the laser went down due to interlock work and Jason and I went into the enclosure (alog91287), things are looking pretty good. The FSS RefCav transmission is drifting down and has generally been lower than we've seen it, so at some point before IR01 we'll go in and realign the FSS path. Next week I'll compare things after the PSL is recovered in the next couple of days.
J. Oberling, R. Short, T. Shaffer
This morning we swapped the temporary SPI shutter cable, for the shutter in the SPI pickoff path on the PSL table, with the permanent one. Once the old cable was removed we fed it out of the PSL enclosure wall penetration to TJ, who then fed the permanent cable into the PSL enclosure for us (thank you, TJ!). The cable was secured in the same was as the temporary cable was, see attached pictures. We tried to physically move the cable into the ALS beam path and were unable to do so; at rest the cable is ~2.5" from the ALS path and the closest we could get it was ~2", so the cable is well secured and unable to drift into the ALS path. This cable had been successfully tested with a spare shutter before installation, but due to the ongoing CDS upgrade we were unable to test it with the installed shutter; this will be done once everything is back up and running. This completes LHO WP 13464.
I took advantage of this morning's earthquake to tweak beam alignment into both the PMC and RefCav, as well as tweaking the amplifier injection currents to attempt to improve both PMC Trans and Refl.
With the ISS OFF, I started with the PMC. At the start PMC Trans was ~102.0 W while PMC Refl was ~29.5 W. After the alignment tweak PMC Trans improved slightly to ~102.9 W while PMC Refl improved to 28.8 W. I then tweaked the amplifier injection currents as shown below:
| Old Injection Current (A) | New Injection Current (A) | ||
| Amp 1 | PS1 | 8.8 | 8.9 |
| PS2 | 8.9 | 9.0 | |
| Amp 2 | PS3 | 9.4 | 9.5 |
| PS4 | 9.5 | 9.6 | |
At the new injection currents PMC Trans is now ~105.0 W and PMC Refl is ~28.5 W. At this point, to get better we will need a few days to redo mode matching into the PMC.
With the PMC done, I turned the ISS ON an adjusted the RefSignal until the diffracted power % was ~4.0%; this is a RefSignal of -1.97 V. I then tweaked beam alignment into the FSS RefCav. Starting TPD was 0.388 V and final TPD is 0.507 V. To improve this further we will need to do an on-table alignment of the FSS beam in the PSL enclosure.
J. Oberling, R. Short, P. Thomas
We have recovered the PSL after this morning's power outage. Once again, the PSL software did not autostart so Patrick was called in to get things up and running. The system calibrations were all correct this time EXCEPT for the operating hours; we trended these to the time of the power outage and updated them manually (the OPHRS A, or the total system uptime, are still incorrect as this field is not updateable and we lost it over multiple failures of the system to retain the calibration settings). I've attached a picture of the current settings screen.
The PMC relocked without issue, although it is running a little cooler than usual ( ~304.5 K vs ~306.0 K). We'll monitor this as the system thermalizes and change the PMC temperature if necessary. The FSS RefCav also locked without issue. We have left the ISS off while the system thermalizes, please do not turn it on until things have settled down (hopefully by the end of the day).
refcav temperature seems to be good as of now. I readjusted the fiber polarization controller and ALSX PLL relocked right away. ALSY PLL relocked after TJ restarted the laser.
This afternoon I recovered the PSL successfully after it had been down since yesterday morning when work on the site laser safety interlock began.
The recovery went as expected and without issue. I've relocked the PMC and FSS, but am leaving the ISS disabled until the amplifiers and PMC have had time to warm up and the output power levels out. Looks like we'll need some alignment touchup into the PMC and RefCav, but that will also wait until things are warmed up, likely sometime tomorrow. Power watchdogs have been enabled for the night.
J. Oberling, R. Short
With the PSL down for safety interlock work, Ryan and I have completed the annual PSL chiller swap. There were no issues with the swap, the backup chiller started right up and has been running for over 1 hour now. We let it run at a higher flow rate (~4.7 lpm) to push any accumulated air out of the line, and then returned it to our operating flow rate of ~2.8 lpm. While the system was down we also changed the system filter; there was some slight yellowing to the filter, but other than that it looked pretty good for being installed for ~15 months. We updated the chiller operating hours in the PSL control software to match the new chiller, 17004.0 hours at time of update. We will continue to monitor the chiller over the course of the day.
The SN of the now in-service PSL chiller is 119247. This closes LHO WP 13413.
I finally got around to doing some slight alignment tweaks this morning following the power outage and PSL recovery a bit over a week ago.
I started with the remotely-controlled picomotors upstream of the PMC to touch up its input alignment with the ISS off:
Some improvement here, but I couldn't quite get the transmitted power back up to the >104 W level it was before the outage. Perhaps amplifier pump diode currents need to be adjusted, or some more invasive alignment tweaks are needed. I then turned the ISS on and adjusted the RefSignal to bring the diffracted power percentage back up to 4% from around 3%, and proceeded with RefCav adjustments:
Again, good improvements, but the highest I've seen this signal get in recent memory is around 550 mV, so the FSS path may need a full tune-up sometime. Not completely surprising, as it's been a while since the last one.
Attaching a screenshot of the quad display after my adjustments for posterity.
We're checking the grounding of things in HAM2. IM4_TRANS QPD, ISS array QPD and all 8 ISS array PDs are fine.
IM4_TRANS and ISS array QPD:
Disconnected the DB25 cable from the transimpedance amp (ISC R4 slot 31) and measured the resistance between the pins and the chamber ground. (Ground potential for the chamber and the racks are significantly different, so we connected one cable directly to the chamber and measured the resistance between that cable and the pins.)
All pins are isolated from the chamber. pin13 is tied to the shielding.
ISS array PDs:
Disconnected two DB25 cables from the second loop chassis (D1600229) in the PSL rack and measured the resistance between the pins and the chamber ground. Same caveat about chamber VS rack ground.
All pins are isolated from the chamber. Pin 13 is not connected to the shielding. This is fine, as this is a special cable made to convert four pairs of coax cables (total 8 coax) into DB25. Shielding of 8 coax is connected to pin14 through pin21 which are tied to the ground inside the second loop chassis. Pin13 is also connected to the ground inside the chassis. See D1600321.
Fil is done with SUS, some issues were found and he'll work with Rahul to try to fix them. He will also test picomotor grounding later.
The HAM2 Suspensions were tested for ground loops. Verified all pins are isolated from chamber ground and pin13 is tied to the shielding. List of cables tested in SUS-R1 listed below. All suspensions pass ground loops checks.
First round of testing produced issues with three cables:
PR3 Middle Cable SUS-HAM2_037 had pin 13 shorted to chamber GND (80 ohms)
PRM/PR3 Cable SUS_HAM2_011 had pin 13 shorted to chamber GND (80 ohms)
PRM Bottom Cable SUS _HAM2_032 Pin 13 and shield not connected
Second round of testing did not show an issue with PR3. PRM issue was a loose pin 13, pin fixed. For the PRM/PR3 short, pin 13 and shield were cut on the connector.
List of cables tested:
MC1 Top Cable SUS_HAM2_001
MC1/MC3 Top Cable SUS_HAM2_002
MC3 Top Cable SUS_HAM2_003
PRM Top Cable SUS_HAM2_010
PRM/PR3 Cable SUS_HAM2_011
PR3 Cable SUS_HAM2_012
MC1 Middle Cable SUS_HAM2_019
MC1 Bottom Cable SUS_HAM2_020
MC3 Middle Cable SUS_HAM2_025
MC3 Bottom Cable SUS_HAM2_026
PRM Middle Cable SUS_HAM2_031
PRM Bottom Cable SUS_HAM2_032
PR3 Middle Cable SUS_HAM2_037
PR3 Bottom Cable SUS_HAM2_038
IM1 Cable SUS_HAM2_168
IM2 Cable SUS_HAM2_181
IM3 Cable SUS_HAM2_184
IM4 Cable SUS_HAM2_169
PICOMOTOR Cable IO_243
R. Short, J. Oberling, J. Kissel
This afternoon we installed the shutter in the SPI pickoff path on the PSL table. We installed it in between the 2 SPI lenses. The cable was tied down with some dog clamps and cable ties, and we checked to make sure it was well clear of all known beams (it doesn't really look like it in the picture, but the shutter cable is ~3 inches away from the ALS beam and cannot drift into its path). Once we ran the cable outside the enclosure, Jeff plugged it into the driver and we ran several on/off tests, with the shutter successfully actuating as expected, every time. I'll update the as-built PSL table layout to include the shutter.
Adding pictures of the current location of the shutter controller outside the enclosure. Final picture is of the controller as it was left; unplugged with the shutter closed.
J. Oberling, P. Thomas, R. Short
TLDR - Following the power outage(s) over the weekend, we've successfully restored the PSL.
Monday morning, Jason started by turning back on the benchtop power supply behind the PSL racks in the LVEA which powers CB2 and then restarted the Beckhoff computer in the diode room (we've seen in the past that the Beckhoff computer needs everything to be powered on before it boots so that it can "see" everything). However, even though the EPICS IOC auto-started when the computer came up, the PLC did not, so we were unable to bring the system up at first. I was able to find and launch the correct PLC (which, for our future reference is in the "Projekt_LIGO_240124" folder), but we noticed after the GUI came up that we were missing the amplifier PD WD, one of the newest additions to the software. Thinking we had an old version of the software somehow, we called in Patrick, who reminded me that instead of just starting TwinCAT in run mode, I should have also logged in and started the PLC to pull in all the updates to the code. This brought the Beckhoff computer back to full functionality, and we were able to bring the laser up without issue after clearing the site laser interlock (which wouldn't clear until the Beckhoff computer was functional). As usual, our calibration settings and operating hours for the NPRO, amps, and chiller were lost with the computer reboot, so we found the last saved screenshot of the settings table we took after the last outage (alog88368) and used it repopulate the table. The operating hours were all fixed also since we could trend back what they were before the outage. A new screenshot of the settings table is attached.
Relocking the PMC went without issue, and it's now been coming up to temperature since Monday with the transmitted and reflected powers slowly settling out. I can tell by the camera spots and the lower transmitted power that some alignment is needed into the PMC, which we can do eventually. The PMC relocked at a temperature a couple degrees cooler than before, which we've seen before, so this slightly different operating point isn't too surprising.
Trending the enclosure temperatures shows that the environmental controls seem to have come back no different than before the outage.
FAMIS 63900
No major events of note this week.
