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Section: H2
Task: PSL
Jennie W, Rahul, Keita
This is just a summary of our work over the last two days trying to repeat the alignment coupling measurements for the replacement ISS array unit (D1101059, unit S1202965). The reason we need to repeat these is because we have now uograded the washer and clamp plate in QPD assembly. See Keita's previous alog for details.
Thursday
First we changed input alignment to get roughly 4 V on each PD in the array, this is acheived by inserting the larger iris and using the two steering mirrors (M2 closest to the array, M1 further towards the laser) to change the input alignment of the auxiliary laser into the unit.
As we have tilted the QPD by adding the new components we need to re-align the QPD to centre the beam (which is split off from the main beam entering the unit by the beam splitter on the elevator assembly which sits at one corner of the ISS array unit).
Then we unscrewed the four screws holding the QPD down (see image) and tried to move the QPD to minimise the coupling from yaw motion if the input beam to pitch. We only managed to minimise pitch coupling and couldn't get it centred on qpd in yaw as the whole QPD unit moves a lot when not screwed down.
We screwed down the QPD but it was still off in yaw by a lot (see image).
As we were adjusting the input alignment mirror to check the coupling I managed to lost the input alignment to the array.
Friday
Today Keita brought the input alignment back by using the beam viewer to check the position on the diodes while changing M2. Then we saw about 3.5-4V on each of the PDs in the array. Next we only undid the two lower screws on the QPD (these hold the QPD unit itself clamped to the platform it sits on, the two upper screws hold in the connector to the back of the QPD and these were only slighly loosened). Keita moved around the unit till the QPD readout showed we were near centred and then we screwed down the unit. It moves alignment while being screwed down probably because of the angle of the QPD relative to the clamp.
For this alignment we used the QPD amplifier unit that gives a live visual readout of the centering.
We also have the option of using another amplifier that gives the QPD X, Y and SUM channels so we can read them on an oscilloscope but these had some weird saw tooth noise on them (see image from Thursday). Keita then discovered that we were using the wrong cable (too low a current rating) for this amplifier, we searched for the correct one but could not find it. We will get back to this on Monday.
Summary: We think we now have the QPD in a good place relative to the PD array as yaw and pitch are fairly decoupled, but maybe the angle of the QPD in rotation is still slightly off as the P and Y motion of the beam are still slightly off from the QPD quadrants. We need a new cable for the ON-TRAK amplifier.
We're assembling the first unit that incooporates all upgrades including the QPD tilt and here are minor problems we've stumbled upon. (No ISS array unit with an upgrade to tilt the QPD (E1400231) has been assembled before as far as I see and nobody seems to have cared to update all drawings.)
First picture is an example of the QPD before upgrade. QPD assembly (D1400139) and the cable connector assembly (D1300222) are mounted on the QPD platform by the QPD clamp plate (D1300963-v1, an older version) and a pair of split QPD connector clamps (d1300220). Two pieces of kapton insulation sheets are protecting the QPD assy from getting short-circuited to the platform.
After the upgrade, the QPD assy sits on top of a tilt washer (D1400146, called beveled C-bore washer) that tilts the QPD by 1.41deg in a plane that divides YAW and PIT plane by 45 degrees (2nd picture). The bottom kapton will go between the washer and the QPD platform plate.
Problem 1: Insulation between the QPD clamp and the QPD pins is a bit sketchy.
Titled QPD means that the bottom of the QPD assy is shifted significantly in YAW and PIT. A new asymmetric QPD clamp plate with tilted seating for the screws (D1300963-v2) has been manufactured to accommodate that. But we have no record of updated kapton insulators, so the center of the clamp bore doesn't agree with the kapton (3rd picture, note that the QPD rotation is incorrect in this picture, which had to be fixed when connecting the cable). Since the tilt washer is not captured by anything (it's just sandwiched between the clamp and the platform plate), it's not impossible to shift the QPD assy such that some of the QPD pins will be grounded to the clamp and thus to the QPD platform plate.
You must check that there's no electrical connection between the QPD assy and the platform each time you adjust the QPD position in the lab.
Problem 2: New QPD connector clamp posts are too long, old ones are too short.
Old posts for the QPD connector are 13/16" long, which is too short for the upgrade because of the tilt washer, see 4th picture where things are in a strange balance. It seems as if it's working OK, but you can wiggle the post a bit so the post slides laterally relative to the clamp and/or the platform, it settles to a different angle and suddnly things become loose. To avoid that, you tighten the screws so hard that they start bending (which may be already starting to happen in this picture).
Also, because the clamp positions are 45 degrees away from the direction of tilt, one clamp goes higher than the other.
To address these, somebody procured 1" and 15/16" posts years ago, but they're just too tall to the point where the clamps are loose. If anything, what we need are probably something like 27/32" and 7/8" (maybe 7/8" works for both).
We ended up using older 13/16" posts, but added washers. Two thin washers for the shorter clamp, two thin plus one thick for the taller one (5th picture). This works OK. Shorter screw is the original, longer screw was too long but it works.
Problem 3: It's easy to set the rotation of the QPD wrong.
When retrofitting the tilt washer and the newer QPD clamp plate, you must do the following.
I screwed up and put the QPD on the connector at a wrong angle. It's easy to catch the error because no quadrant responds to the laser, but it's better not to make a mistake in the first place. It will help if the QPD assy barrel is marked at the cathode-anode1 corner.
It seems that D1300222 and D1101059 must be updated. Systems people please have a look.
D1300222: A tilt washer (D1400146), a new QPD clamp (D1300963-v2) and two sheets of kapton insulation are missing. Spacers are longer than 13/16".
D1101059: Explicitly state that part #28 (D1300963, QPD clamp) must be D1300963-v2.
I installed the beam dumps (which are two plates of filter glass, probably from Schott?) for the array after cleaning them according to E2100057.
There are marks that look like water spots and/or some fog that couldn't be removed by repeated drag wiping with methanol (see picture).
After installation, I found that these plates are very loosely captured between two metal plates, see the video, this seems to be by design. I don't like it but the same design has been working in chamber for years.
Sheila measured the CARM gain during vent recovery at a thermalized time (84944), and it seemed low, so today we plugged in the SR785 and measured the CARM OLG at the start of lock.
Right at the beginning of lock, the UGF was 14.4 Hz, which is fine except that we will lose gain from thermalization. I bumped up the gain by 1 dB on each REFL A and B slider ("H1:LSC-REFL_SUM_{A,B}_IN2GAIN") and remeasured, and the UGF was about 14.3 Hz. Then, I increased the gain another 2 dB each on each slider and remeasured, 16 kHz. This is where we want to be, although I imagine it will decay more as we thermalize.
This means that in NLN, we want our CARM gain settings to be 15 dB on each slider, which I accepted in SDF. However, I have not yet put them in the guardian because I am trying to figure out where that actually should be adjusted.
I have attached the three measurements I took. The title of the first one is misleading since I used the wrong template, but the time stamps on all are accurate.
Second measurement, both gains up +1 dB
Third measurement, both gains up +2 dB more
Procedural notes for future me to measure the OLG and plot the measurement:
> cd ligo/gitcommon/psl_measurements/templates
> conda activate psl
> python ../code/SRmeasure.py carm_olg_template.yml
> python ../code/quick_tf_plot.py ../data/carm_olg/[filename]
I unplugged the SR785 before observing.
I see now, with Keita's help, that I changed the "wrong" gain sliders, because I should have adjusted the "H1:LSC-REFL_SERVO_IN{1,2}GAIN" sliders. However, jsut based on how things are connected, I don't think it is having an overall different effect right now. But, to do this properly, I am updating the guardian code on line 5882:
This is for FAMIS #26427.
Laser Status:
NPRO output power is 1.844W
AMP1 output power is 70.07W
AMP2 output power is 140.3W
NPRO watchdog is GREEN
AMP1 watchdog is GREEN
AMP2 watchdog is GREEN
PDWD watchdog is GREEN
PMC:
It has been locked 3 days, 0 hr 25 minutes
Reflected power = 23.23W
Transmitted power = 105.5W
PowerSum = 128.7W
FSS:
It has been locked for 0 days 0 hr and 5 min
TPD[V] = 0.8216V
ISS:
The diffracted power is around 4.0%
Last saturation event was 0 days 0 hours and 32 minutes ago
Possible Issues:
PMC reflected power is high
Now that we're at 60 W of input power, I double checked the ISS secondloop array pointing after the vent. We're missing slightly, seemingly pitched off the ISS QPD. The ndscope has Y1 dashed white lines at where the ISS PD values are now. The ISS secondloop PD values from March 12 are the actual traces. We're still locking, and so I leave ISS picoing undone for now. We'll have to leave the ISS secondloop open and pico back onto the array at some point. Based on the attached PSD, this could be responsible for our huge peak at 29 Hz in DARM.
This is for FAMIS #26419.
Laser Status:
NPRO output power is 1.863W
AMP1 output power is 70.07W
AMP2 output power is 140.4W
NPRO watchdog is GREEN
AMP1 watchdog is GREEN
AMP2 watchdog is GREEN
PDWD watchdog is GREEN
PMC:
It has been locked 11 days, 1 hr 18 minutes
Reflected power = 23.1W
Transmitted power = 105.5W
PowerSum = 128.6W
FSS:
It has been locked for 0 days 0 hr and 5 min
TPD[V] = 0.8038V
ISS:
The diffracted power is around 4.0%
Last saturation event was 0 days 0 hours and 55 minutes ago
Possible Issues:
PMC reflected power is high
This is for FAMIS #26416.
Laser Status:
NPRO output power is 1.842W
AMP1 output power is 70.19W
AMP2 output power is 140.3W
NPRO watchdog is GREEN
AMP1 watchdog is GREEN
AMP2 watchdog is GREEN
PDWD watchdog is GREEN
PMC:
It has been locked 4 days, 6 hr 50 minutes
Reflected power = 23.09W
Transmitted power = 105.5W
PowerSum = 128.6W
FSS:
It has been locked for 0 days 0 hr and 14 min
TPD[V] = 0.82V
ISS:
The diffracted power is around 3.9%
Last saturation event was 0 days 3 hours and 31 minutes ago
Possible Issues:
PMC reflected power is high
Betsy, Camilla, Keita, Jason This morning, we took a closer look at eh small PSL-ALS beam path hitting the 1 and only mirror in HAM1 before heading to IOT1. It looked a bit clipped/elongated and was coming out of the light pipe toward the -Y side and veering off course onto the table (when compared to the new layout map). Given work on the path on the PSL table (for SPI), Jason and Keita went in to the PSL and revisited how the beam launches at the periscope. They could see scatter somewhere in the light pipe so it was probably clipping in there. Using the top ALS periscope mirror, Jason was able to yaw the beam back to the designed position of the mirror in HAM1 (Keita on the phone with Jason in the box, relaying to Betsy who moved the mirror and beam dump on HAM1). Now the beam looks nicely round, more centered in the entry viewport window, and runs along the table per the map we are aligning to D1000313-v19. We pointed the steering mirror so the beam leaves the table to also match the map. Next up is the X-arm peek and tweaking of alignments to get onto the IOT1 periscope mirrors.
First attachment shows the beam right after the viewport, shot by Betsy's cellphone. The beam looked much worse to my eyes on the viewer card.
Anyway, Jason and I found that
3rd attachment shows ALS-L2 where the beam was offset by about half of the open aperture radius of the lens mount (the lens itself is 1").
We used ALS-M2 and ALS-M3 to recenter the beam on two reference irises. 4th attachment shows ALS-L2 after this adjustment where the beam is more centered. Not perfect but much better.
On the 5th picture the beam shows no sign of clipping but the beam is close to the -Y edge of the baffle hole for the viewport.
Next Jason moved the top periscope mirror to steer the beam to where it's supposed to be in HAM1. The beam looked more centered on the baffle (6th picture).
7th picture: The location of the steering mirror for this beam on HAM1, which was set according to the HAM1 layout drawing.
8th and 9th show the PSL-ALS beam right after it is reflected by the steering mirror, and right before it leaves HAM1. We might have to fine-adjust this.
As Keita notes, before yawing the top periscope mirror he and I checked the 2 ALS alignment irises that sit under the periscope between mirrors IO_ALS_M3 and IO_ALS_M4 (the bottom ALS periscope mirror). The beam was off on both alignment irises to the -Y side, suggesting a beam shift had occured sometime between the end of the PSL laser upgrade in Jan 2022 and now (the last time I recall looking at this alignment was at the end of the laser upgrade); using an IR viewer Keita looked at the beam on IO_ALS_L2 (the 2nd ALS mode matching lens) and the beam was off-center on the lens as well. The beam looked decently well aligned (not perfect) along the IO_ALS_M1 to IO_ALS_M2 path, but beyond that it was well off. It's unclear what casued this shift. There was the recent SPI pickoff install last month that potentially could have bumped IO_ALS_M2, since they were working in that area, but I don't think that alone would be enough to cause the shift we saw. The beam needed to be walked in the +Y direction using both IO_ALS_M2 and IO_ALS_M3 to re-center on the alignment irises, but bumping only a single mirror would more than likely have caused an angular shift in the beam and be easily corrected using only the mirror that was bumped. This defintely was not the case, as we needed both IO_ALS_M2 and IO_ALS_M3 to walk the beam back to the irises. So as of right now I cannot say what caused this misalignment, it's entirely possible the ALS beam has been misaligned for a while.
As noted above, we used IO_ALS_M2 and IO_ALS_M3 to re-center the ALS beam on the alignment irises, and at this point the beam was no longer clipping when traversing the ALS light pipe. Back on the HAM1 table, the mirror that directs the ALS beam onto ISCT1 was still too far in the -Y direction for comfort (getting a little to close to the future home of the JAC and its associated optics). I then went into the enclosure and yawed IO_ALS_M5 (the top ALS periscope mirror) until the mirror in HAM1 was in its as-designed location. I've attached a picture I took of how the ALS beam now looks when entering the ALS light pipe; it's now a little closer to the +Y edge of the light pipe. Before adjustment the outside edge of the beam was very roughly 1" or so away from the light pipe edge (did not get a picture of this), now it's very roughly 1/2" or so away from the edge.
Closes FAMIS 26397, last checked in alog 84018
Laser Status:
NPRO output power is 1.841W
AMP1 output power is 70.43W
AMP2 output power is 140.4W
NPRO watchdog is GREEN
AMP1 watchdog is GREEN
AMP2 watchdog is GREEN
PDWD watchdog is GREEN
PMC:
It has been locked 2 days, 23 hr 11 minutes
Reflected power = 23.28W
Transmitted power = 105.5W
PowerSum = 128.8W
FSS:
It has been locked for 1 days 20 hr and 35 min
TPD[V] = 0.8003V
ISS:
The diffracted power is around 3.7%
Last saturation event was 1 days 20 hours and 35 minutes ago
Possible Issues:
PMC reflected power is high
WP 12463: This will close this FRS: https://services1.ligo-la.caltech.edu/FRS/show_bug.cgi?id=5861
We changed PSLFSS and PSLPMC model and related MEDM screens and confirmed that the PMC and FSS relocked right away before RyanS started his work in the PSL room. Guardian was modified to accomodate this. Safe SDF for PMC and FSS were updated.
(FYI, the motivation for this ancient ticket was to kill the habit of using arbitrary number for ON/OFF status, which was really bad in all PSL models. Depending on who wrote what, sometimes 1 means ON, sometimes -1, some other times -30000, and these status were cdsEpicsInput which are floating point. Now they're cdsEpicsBinIn, which is binary, ON is 1, OFF is 0.)
I pulled pslfss and pslpmc model from svn to close the FRS above. We'll have to keep some local modifications unique to LHO at least until the end of the run. Due to local changes, the models will not be committed to SVN upstream.
Changed models: ${userapps}/release/psl/common/models/pslfss.mdl, ${userapps}/release/psl/common/models/pslpmc.adl, ${userapps}/release/psl/h1/models/h1pslfss.mdl.
See the first two screen shots.
Local modifications 1: Adding back CALI filters.
These filters are not used any more from this point on. However, removing these from DAQ means that we cannot trend the data of these back without using NDS2 and specifying epoch, which is not a great thing to do in the middle of the run.
See the first and second screen shot (red in the left panel).
Local modifications 2: Move NPRO_TEMP_OUT out of the common model and into the H1 model.
Dave originally added NPRO_TEMP_OUT channel to DAQ at 256Hz locally to the common FSS model in May 2023. However, he moved it to h1pslfss.
Local modifications 3: Don't change binary to DAC count and convert it back to binary
There was such a block in the common PMC model in the SVN (1st screen shot, right panel, green), which was eliminated in the local common model for the sake of simplicity.
Local modifications 4 (cosmetic): Define a constant representing DAC count that will produce +10V in the model.
Blue in the first two screen shots.
Dave thinks that this needs to be in the top level of local models (not in the common model) right before the signal goes to DAC in the future. That way, when we upgrade the DAC we can just change the constant.
Manually changed: ${userapps}/release/psl/common/medm/PSL_PMC.adl as the file on SVN still uses the old logic.
Pulled from SVN: ${userapps}/release/psl/common/medm/PSL_FSS.adl and ${userapps}/release/psl/common/medm/FSS/MAN.adl (and other things in FSS directory).
In isc_library.py,
L200 if ezca['PSL-PMC_LOCK_ON'] != -30000:
was changed to
L200 if ezca['PSL-PMC_LOCK_ON'] == 0:
In LASER_POWER.py,
L157 elif self.timer['wait_for_busy'] and ezca['PSL-ROTATIONSTAGE_STATE_BUSY'] == 0 and ezca['PSL-PMC_LOCK_ON'] == -30000:
L161 elif self.timer['wait_for_busy'] and ezca['PSL-ROTATIONSTAGE_STATE_BUSY'] == 1 and ezca['PSL-PMC_LOCK_ON'] == -30000:
were changed to
L157 elif self.timer['wait_for_busy'] and ezca['PSL-ROTATIONSTAGE_STATE_BUSY'] == 0 and ezca['PSL-PMC_LOCK_ON'] == 1:
L161 elif self.timer['wait_for_busy'] and ezca['PSL-ROTATIONSTAGE_STATE_BUSY'] == 1 and ezca['PSL-PMC_LOCK_ON'] == 1:
See screen shots 3 and 4. (You can see that the old setpoints were float and the new setpoints are binary.)
It's not shown in the last screen shot but I accepted H1:PSL-FSS_AUTOLOCK_ON in the afternoon after RyanS locked the FSS again.
H1:PSL-PMC_LOCK_ON, H1:PSL-PMC_TF_IN_ON, H1:PSL-PMC_RAMP_ONI, H1:PSL-PMC_ALIGNRAMP_ON, H1:PSL-PMC_BOOST, H1:PSL-PMC_BLANKING, H1:PSL-FSS_AUTOLOCK_ON, H1:PSL-FSS_TEST1_ON, H1:PSL-FSS_TEMP_LOOP_ON_REQUEST
For these channels, 0 (zero) means OFF, and non-zero means ON. This doesn't change. It's just that many numbers like -1 and 1 and -30000 used to be used as "non-zero" depending on who wrote what, but from this point "non-zero" can only mean 1.
However, due to the change from float to integer, if you trend these channels, non-zero value for the data older than 10AM-ish Pacific on Apr/22/2025 is not displayed correctly. Fortunately zero is still zero (Jonathan confirmed), so if you trend the data to see if something was ON, check that the channel was not zero, i.e. H1:PMC-TF_IN_ON != 0 rather than H1:PMC-TF_IN_ON == -30000.
H1:PSL-FSS_TEST2_ON
Semantics of this signal changed. It used to be that ON=0 (zero) and OFF=1 to compensate the inverted logic in the hardware, but now ON=1, OFF=0 as the logic inversion is in the model.
The same caveat about float to integer applies. If you want to trend this channel, check H1:PSL-FSS_TEST2_ON ~=0 rather than H1:PSL-FSS_TEST2_ON == 1, and then you have to be aware that H1:PSL-FSS_TEST2_ON ~=0 means OFF for data older than 10AM-ish Pacific on Apr/22/2025, but the same thing means ON for newer data.
The PSL picomotor controls have been moved from the ISC Driver to the PSL Driver installed in the PSL-R2 Rack (alog 63613, alog 62830). The new DB25 cable is routed from behind the PSL field rack into the enclosure. The old controls cable was pulled out of the enclosure and will be reused for HAM1/JAC. Ryan Short is testing picomotors are operational through MEDM.
F. Clara, R. McCarthy, R. Short
I moved the picomotor breakout box (D1101691-v1) from its previous location on top of the water pipes between the PSL table and the north wall of the enclosure (first picture) to underneath the center of the table (second picture) to accommodate the new DB25 cable coming from the west wall out to the PSL racks. New cable was routed through the floor cable manager and DB9 cables up to the table were coiled under the table to account for extra length. Cable routing from the breakout box up to and on the PSL table are unchanged.
I also tested all eight picomotors (four for the two mirrors for PMC steering, four for the two mirrors for RefCav steering) and all are working well and as expected.
J. Kissel scribing for S. Koehlenbeck, J. Freed, and R. Short ECR E2400083 IIET 30642 WP 12453 Just writing a separate explicit aLOG for this for ease of reference in the future. Before, during and after the SPI install we measured power along respective paths, (1) The p-pol in-coming power into the whole ALS / SQZ / SPI pick-off path, (2) The "ALS COMM" path: p-pol power in transmission of the ALS-PBS01 with the newly modified ALS-HWP2 position to get more power total power in the paths (3) and (4), (3) The "SPI pick-off" path: The ~s-pol power in reflection of SPI-BS1, (4) The "ALS/SQZ Fiber Distribution" path: ~s-pol power in transmission of SPI-BS1, (see discussion in LHO:83978 as to why we're not so confident the reflection from ALS-PBS01 is entirely s-pol, which is why I say "~s-pol" here.) The BEFORE vs. AFTER power in these paths is as follows: Path Measured Between Raw Power [mW] PMC TRANS [W] Date/Time Measured Scaled Power [mW] Fractional Power [%] (1) ALS-L1 and ALS-HWP2 2060 103.2 2025-04-15 21:39 UTC 2095.9 --- % BEFORE (2) ALS-M2 and ALS-L2 1970 102.8 2025-04-15 22:17 UTC 2012.2 96% (4) ALS-M9 and ALS-FC2 48.7 103.0 2025-04-15 21:48 UTC 49.646 2% % AFTER (2) ALS-M2 and ALS-L2 1790 103.3 2025-04-17 21:13 UTC 1817.7 87% (3) SPI-L1 and SPI-L2 186 103.5 2025-04-16 22:43 UTC 188.7 9% (4) ALS-M9 and ALS-FC2 50.5 103.5 2025-04-16 22:43 UTC 51.232 2% where I've scaled all the raw power measurements by the rough nominal PMC TRANS power during recent observing times, 105 [W], i.e. (Scaled Power [mW]) = (Raw power) * (105 [W] / PMC TRANS [W]) and (Fractional Power [%]) = 100 * {Scaled Power [mW]; paths (2)-(4)} / {Scaled Power [mW]; path 1} As Ryan mentions in LHO:83989, for the purposes of safe long term storage, after all was said and done, we rotated SPI-HWP1 such that only 20 [mW] would go toward the SPI-FC1 fiber collimator, and it's dumped upstream just after SPI-L1. These AFTER power levels are what we anticipate running the rest of O4 in, with the SPI pick-off path safely out of commission. 2W Measurements Head: Ophir 10A-V2-SH SN122042 Readout: Ophir 20C-SH SN171175 Accuracy: +/-3% 200 mW Measurements: Head: Thorlabs S401C Readout: Thorlabs PM100-D Accuracy: +/- 7% The attached picture summarizes all this info. The picture was take midday 2025-04-17, so you see the Ophir power meter in the middle of the ALS COMM
J. Kissel scribe for S. Koehlenbeck, J. Freed, R. Short, and guest star J. Oberling ECR E2400083 IIET 30642 WP 12453 Toward the end of day two of install (LHO:83961), the team set the power at the input of the ALS-FC2 by rotating ALS-HWP2, to be 50.5 [mW] (with PMC TRANS at 103.5 [W]). The reported power for the on-table ThorLabs SM1PD1A, however, measured consistently lower at "31 [mW]," lower than the goal for this PD, a reported power of "45 [mw]" (LHO:83927), when the power of the beam between ALS-M9 and ALS-FC2 was physically measured at 48.7 [mW] (with PMC TRANS at 103.0). We think lower reported power on the PD is related to (1) The slight translation of the what-used-to-be ALS-L5 to ALS-M9 beam, because of the thickness of the SPI-BS1 that was inserted into that path, and (2) a change in the amount of s- and p- polarization in reflection of the ALS-PBS01 after rotating ALS-HWP2 to increase the power in the ALS/SQZ/SPI path, because the polarization state of the reflection of a PBS can be power dependent. To support (2), we measured the polarization today between ALS-M9 and ALS-FC2 with a temporary PBS and power meter. On 2025-04-17 at 19:02 UTC with PMC power at 103.7 [W], we measure s-pol = 49.7 [mW] p-pol = 1.8 [mW] (total = 49.7 + 1.8 = 51.5 [mW]) Regrettably, we did not measure this polarization state prior to changing anything. However, because we've *measured* equal total power at ALS-FC2 before vs. after, we're confident that at least the total power going into ALS-FC2 is the same. As such, we called in Jason to help couple the beam into ALS-FC2 using ALS-M9 and what alignment screws are on ALS-FC2 itself. Attached is the trend of that process, where we used the SPI distribution chassis PD in two forms: H1:ALS-C_FIBR_INTERNAL_DC_POWER never calibrated version, used to be 0.1 [cts] H1:ALS-C_FIBR_INTERNAL_DC_POWERMON version we'd been using, calibrated into [mW] In the end, we landed with the values of these channels at H1:ALS-C_FIBR_INTERNAL_DC_POWER 0.1 [cts] H1:ALS-C_FIBR_INTERNAL_DC_POWERMON 31.4 [mW] which matches our goals from LHO:83927. The team also adjusted the position of the SM1PD1A in transmission of ALS-M9 to account for (1). However, even after moving the PD out of maximum and back, they were not able to find any position where the PD readout exceeded H1:ALS-C_FIBR_EXTERNAL_DC_POWERMON 31.0 [mW] This why we expect that something more like (2) is going on. Though we looked through - E1300483 (doesn't list ALS-M9), - E1900246 (calls the optic ALS-M6, which is not for 1064 nm in E1300483), - E0900325 (isn't new enough to have this mirror), - Peter King's purchase orders circa 2019 (Req 122638553 for the fiber collimator parts, and Req 122583017 for the SM1PD1A parts) we couldn't find anything that was clearly and obviously the ALS-M9 optic, so we can't validate or reconstruction the reflectivity in each polarization to model the factor of 31 [mW] / 45 [mW] = 0.7x (or 30% drop) reported value change. In any event, this EXTERNAL PD channel will need to be recalibrated to better reflect the real power in this path. Also, when we re-start up anything that uses the output of the ALS / SQZ fiber distribution, it may need to be adjusted to account for the polarization change described in (2)
S. Koehlenbeck, J. Freed, R. Short, J. Kissel
The mode matching of the PSL pick-off beam to the SPI fiber collimator has been implemented using two lenses. The target beam has a mode radius of 550 µm at a position 63.5 cm downstream from the SPI beamsplitter (SPI-BS).
The lens configuration that produced the closest match to the target mode used:
L1: Focal length = 100 mm
L2: Focal length = 60 mm
Attached is a beam profile fit performed using JaMMT on data acquired with a WinCamD of the beam after SPI-L2. The measured beam radii at various distances from the SPI-BS are as follows:
| Distance (cm) | Horizontal Radius (µm) | Vertical Radius (µm) |
|---|---|---|
| 70.734 | 476 | 542 |
| 91.054 | 470 | 543.5 |
| 116.454 | 558.5 | 616.5 |
Both lenses are oriented such that their planar sides face the small beam waist between the two lenses. The arrows on the lens mounts point toward the convex surfaces.
The power transmission through the fiber has been measured to be 83 %.
ECR E2400083 IIET 30642 WP 12453 Some "for the record" additional comments here: - Sina refers to the "SPI-BS" above, which is the same as what we've now officially dubbed as "SPI-BS1." - Lenses were identified to be needed after the initial measurement of the beam profile emanating from SPI-BS1. That initial beam profile measurement is cited in LHO:83956, and the lens also developed in JaMMT with the lenses that were available from the optics lab / PSL inventory. - If anyone's trying to recreate the model of the beam profile from the two measurements (LHO:83956 with no lenses, and the above LHO:83983) just note that the "zero" position is different in the quoted raw data; in LHO:83956 is the front of the rail, on Column 159 of the table, and in LHO:83983 the zero position is the SPI-BS1 reflective surface which is on Column 149 of the table, i.e. a 10 inch = 25.4 cm difference. - The real SPI-L1 installed to create this mode-shape / beam profile is labeled by its radius of curvature, which is R = 51.5 mm, and thus its focal length is more precisely f = R*2 = 103 mm. (We did find a lens that does have f = 60 mm for SPI-L2, and it's labeled by its focal length.) - "the fiber" is that which is intended for permanent use, depicted as SPI_PSL_001 in the SPI optical fiber routing diagram D2400110, a Narrow Key PM-980 Optical Fiber "patch cord" from Diamond, whose length is 30 [m]. This fiber will run all the way out to SUS-R2, eventually, to be connected as the input to the SPI Laser Prep Chassis (D2400156). - Per design, light going into this fiber is entirely p-pol, due to polarization via SPI-HWP1 and clean-up by SPI-PBS01 just upstream. We did not measure the polarization state of the light exiting the fiber. - The raw data that informs the statement that "the power transmission thru the fiber has been measured to be 83%": : We measured the input to the fiber coupler, SPI-FC1, via the S140C low-power power meter we'd been using throughout the install. The output power was measured via a fiber-coupled power meter Sina had brought with her from Stanford (dunno the make of that one). : We measured the power input to the fiber twice several hours apart (with the change in fiber input power controlled via the SPI-HWP1 / SPI-PBS01 combo)., (1) 19.9 [mW] with PMC TRANS power at 104.1 [W] at 2025-04-17 16:35 UTC (while the PMC power was in flux from enviromental controls turn on) (2) 180 [mW] with PMC TRANS power at 103.5 [W] at 2025-04-17 14:00 UTC (while the PMC power was quite stable) : We measured the output power (1') 16.6 [mW] with PMC TRANS power at 103.7 [W] at 2025-04-17 17:35 UTC (an hour later than (1)) (2') 150 [mW] with PMC TRANS power at 103.5 [W] at 2025-04-17 14:00 UTC (simultaneous to (2)) : Thus derive the transmission to be (1'') (16.6 / 19.9) * (104.1/103.7) = 0.837 = 83.7% and (2'') (150 / 180) * (103.5/103.5) = 0.833 = 83.3%
In the attachment you will find the JAMMT model for the measured beam profile of the PSL pick off with the origin a SPI-BS1, as well as the lenses used to adjust the mode of the beam for the fiber collimator FC60-SF-4-A6.2-03.
[Betsy, Keita, Camilla, Richard M., Elenna]
After the power outage, we wanted to get some confirmation of PZT pointing out of the PSL. Betsy, Keita and Camilla went in the cleanroom with the IR viewer and indicator cards and took the covers off the IMC refl and trans viewports on HAM2. Keita found the beam out of the IMC REFL viewport, and I adjusted the IMC PZT in pitch and yaw under direction from Keita. I accidentally moved the pitch slider a bit at the beginning due to user error. Then, we took large steps of 1000 or 2000 counts to move the offsets in pitch and yaw.
Start values: pitch: 22721, yaw: 5488
End values: pitch: 21192, yaw: 6488
Then, Betsy found the beam out of the IMC TRANS viewport and Richard marked the beam spot approximately on the outside of the cleanroom curtain with a red sharpie. This is super rough but gives us a general location of the beam. We think this is a good enough pointing recovery to proceed with vent activities.
During this work, PSL waveplate rotetor was set to 200mW and then de-energized. I haven't re-energized as we don't need higher power for a long time.
PSL laser pipe was temporarily opened for this task and was closed after.
Attached video shows the flashing of the beam in MC TRANS path. The alignment from the PSL through the IMC is not crazy. Any further refinement should be done after we start pumping down the corner before we install HAM1 optics.
Accepting PZT offsets in h1ascimc SAFE.snap table.
Closes FAMIS 26832, last checked in alog 83610
Laser Status:
NPRO output power is 1.829W
AMP1 output power is 70.43W
AMP2 output power is 141.1W
NPRO watchdog is GREEN
AMP1 watchdog is GREEN
AMP2 watchdog is GREEN
PDWD watchdog is GREEN
PMC:
It has been locked 1 days, 20 hr 16 minutes
Reflected power = 22.99W
Transmitted power = 105.7W
PowerSum = 128.7W
FSS:
It has been locked for 0 days 20 hr and 13 min
TPD[V] = 0.8222V
ISS:
The diffracted power is around 4.1%
Last saturation event was 1 days 20 hours and 15 minutes ago
Possible Issues: None reported
Not sure what did it to the PSL's FSS, but noticed we were stuck before the PRC portion of Initial Alignment, and DIAG MAIN had the following messages flashing like the devil:
On the FSS screen, the autolocker was going wild and the PZT_MON screen was all over the place.
Since the Autolocker was having issues, I toggled the autlocker off/on and this immediately calmed down the FSS and the IMC finally locked back up.
Going to restart the Initial Alignment. Because the winds are still pretty attrocious.
TITLE: 03/27 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 153Mpc
OUTGOING OPERATOR: Ibrahim
CURRENT ENVIRONMENT:
SEI_ENV state: CALM
Wind: 18mph Gusts, 10mph 3min avg
Primary useism: 0.03 μm/s
Secondary useism: 0.34 μm/s
QUICK SUMMARY: Locked for 3 hours. DIAG_MAIN is reporting "RefCav transmission low", tagging PSL. No other alarms or notifications. Planned calibration and commissioning time today from 1530-1900 UTC.
Closes FAMIS 26373. Last Checked in Alog 83229
Laser Status:
NPRO output power is 1.845W
AMP1 output power is 70.39W
AMP2 output power is 140.3W
NPRO watchdog is GREEN
AMP1 watchdog is GREEN
AMP2 watchdog is GREEN
PDWD watchdog is GREEN
PMC:
It has been locked 40 days, 2 hr 27 minutes
Reflected power = 22.39W
Transmitted power = 106.6W
PowerSum = 129.0W
FSS:
It has been locked for 0 days 9 hr and 26 min
TPD[V] = 0.8039V
ISS:
The diffracted power is around 3.5%
Last saturation event was 0 days 10 hours and 2 minutes ago
Possible Issues: None reported
