Displaying reports 1601-1620 of 83211.Go to page Start 77 78 79 80 81 82 83 84 85 End
Reports until 13:29, Monday 21 April 2025
H1 CDS
david.barker@LIGO.ORG - posted 13:29, Monday 21 April 2025 (84030)
RO returned to CDS cell phone alarms. Alarms added for EDC

The FMCS Reverse Osmosis (RO) system has been error free for 10 days following the water leak repair. Its alarms have been returned to the CDS cell phone alarm system.

Following the crash of h1susauxh2 over the weekend, I reviewed the alarm configuration to see if we would get cell phone alarms if something happened to h1edc which runs on h1susauxb123. To this end I have added two new alarm channels to the alarms system.

Both of these changes went into effect at 13:20 PDT when the alarms.service was restarted on cdslogin.

LHO VE
jordan.vanosky@LIGO.ORG - posted 13:14, Monday 21 April 2025 (84028)
LN2 Dewar Inspection 4/21/25 and Vacuum Jacket Pressures

A Norco tech came to the site to inspect the 8 LN2 dewars that feed the cryopumps. Inspection report will be posted to Q2000008 once received.

- No major issues found, some small leaks were repaired as they were found

The vacuum jacket pressures were also measured during inspection:

The vacuum jackets were all pumped down to <10 mtorr last May (excluding CP4 which is not in use), see alog 77742

Dewar Pressure (micron/mtorr)
CP1 12
CP2 21
CP3 215
CP4 (not in service) 220
CP5 12
CP6 10
CP7 16
CP8 9
H1 AOS
daniel.sigg@LIGO.ORG - posted 13:07, Monday 21 April 2025 - last comment - 15:52, Tuesday 29 April 2025(84027)
OSEM reabacks for RMs

Fil Marc Daniel

We noticed that the photodiode pins of the in-air cable that connects to RM1 and RM2 were flipped. This will flip cathode and anode which will only matter if there is a bias applied.

Going thru the schematics it seems that with 1:1 wiring the PD anode and cathode are flipped compared to what is shown in Sat Amp D080276. I assume somebody noticed this and flipped the corresponding pins of the in-air cable to correct for it back in 2013.  The polarity of the PD doesn't really matter, if there is no bias. We checked the RM sat amps and they have no bias.

If the Sat Amp PDs are connected as shown om D080276, the OSEM values will be negative. Indeed, the RMs had negative OSEM values as expected. However, all ZMs have positive values, since nobody bothered to flip the pins. We propose to no longer flip the PD pins for the RMs and work with positive OSEM values in the future.

Comments related to this report
jeffrey.kissel@LIGO.ORG - 15:52, Tuesday 29 April 2025 (84176)CDS, ISC, SUS, SYS
J. Kissel

First, supporting Daniel's findings that the RM1 and RM2 HTTS OSEM sensor readbacks have been incorrectly negative for ages, I attach a trend of the OSEM ADC input values (and OSEMINF OFFSETS and GAINs) back to 2017.

Not said explicitly in the above aLOG -- Daniel / Fil / Marc installed fresh new DB25 Sat Amp to Vac Feedthru cables (D2100464) just after this aLOG as a part of cabling up the new signal chain for PM1. These cables are one-to-one pin-for-pin cables so it *should* have played no role in the sign of the sensors or how they're connected. 

However, it's now obvious that RM1 and RM2 have had the ADC input voltages as negative for a *very* long time. 

I reviewed the signal chains for the OSEM PDs; see G2500980.

The RMs are using a US 8CH satamps D1002818 / D080276.

I attach a screen-cap of page 4, which highlights that 
    - UK 4CH satamps D0900900 / D0901284 use 
        . a negative reverse bias configuration, with
        . anode connected to bias and cathode connected to the negative input of the TIA, and
        . an inverting differential amplifier stage
    - US 8CH satamps D1002818 / D080276 use 
        . a positive reverse bias configuration, with 
        . cathode connected to the bias and anode connected to the negative input of the TIA, and [hence the apparent "pin-flip" from the other two satamp types]
        . a non-inverting differential amplifier stage
    - US 4CH satamps D1900089 / D1900217use 
        . a negative reverse bias configuration, with
        . cathode connected to the bias and anode connected to the negative input of the TIA, and
        . a non-inverting differential amplifier stage [hence the overall "sign flip" from the other two]

I disagree with Daniel that "the polarity of the PD" i.e. how the anode and cathode are connected to the transimpedance amplifier.
All versions of the PD pinout + SatAmp configure the system in a reverse bias, be it negative or positive. 
In these configurations, even in a zero bias configuration, photocurrent always flows from from cathode to anode as light impinges on the PD. 
So if the anode is hooked up to the negative input of the transimpedance amp (as in D1002818), that signal will have a different sign than if the cathode is hooked up to the negative input (as in D0900900 and D1900089).

The RMs should have their *positive* bias from the D080276 circuit applied.
In 2011, we'd agreed in G1100856 to jumper all OSEM satamps to the "L" position, a.k.a. the LIGO OSEM a.k.a. AOSEM position, which uses a bias voltage and is thus in photo conductive or pc mode. This is mostly because we wanted to not have to think about keeping track of which satamps are jumpered and which are not, but also because the BOSEM PD didn't mind have a bias, even though it was designed to have no bias.

Given the "thought of 2nd to last, last, and never" history of the RMs as they traversed subsystem from ISC to SUS circa O1, moving from the ASC front-end to a SUS front-end circa O2, then never really appearing in wiring diagrams until O3, etc. it wouldn't surprise me if the RMs didn't get the memo to put the bias jumper in the "L" position jumpering pins 2 and 3.

I disagree with Daniel: only the US 4CH satamp D1900089 / D1900217 should read negative with light on it.

So, my guess is that that someone "in 2013" (i.e. during aLIGO install prior to O1) didn't understand these subtleties between the UK 4CH and US 8CH satamp, saw the "different from UK 4CH satamp" and tried fixing the pins of the in-air D25 from satamp to vacuum flange.

Regardless, the new cable has cleared up the issue, and ADC voltage from RM1 and RM2 is now positive.
Images attached to this comment
H1 CDS
david.barker@LIGO.ORG - posted 12:59, Monday 21 April 2025 (84026)
h1lsc and h1asc model changes

WP12472 POP_X and LSC_REFL_B changes

Daniel, Erik, Dave:

New h1lsc and h1asc models were installed at 12:50 PDT. No DAQ restart was required.

h1lsc restart caused TIM errors in h1ioplsc0 and h1sqz.

Images attached to this report
H1 PSL
ryan.short@LIGO.ORG - posted 10:56, Monday 21 April 2025 (84022)
PSL 10-Day Trends

FAMIS 31082

Generally, things are stable following the three days of work in the enclosure for the SPI pick-off path install last week, which show clearly on several trends. Most notable is the decline in PMC and RefCav transmission, which have significant misalignments as seen by the beam spot cameras. Fil and I plan to switch the connection of the picomotors to their new driver tomorrow, so after that they'll be usable again and I'll touch up the alignments.

Also, we have still not increased the pump currents for AMP1 as we noticed last week following the power outage. This should bring the power out of both amplifiers and the PMC closer to their levels pre-outage.

Images attached to this report
LHO VE
david.barker@LIGO.ORG - posted 10:20, Monday 21 April 2025 (84021)
Mon CP1 Fill

Mon Apr 21 10:08:36 2025 INFO: Fill completed in 8min 32secs

 

Images attached to this report
H1 PSL
anthony.sanchez@LIGO.ORG - posted 08:21, Monday 21 April 2025 (84018)
PSL Weekly Checks

FAMIS 26393

Laser Status:
    NPRO output power is 1.843W
    AMP1 output power is 69.23W
    AMP2 output power is 139.7W
    NPRO watchdog is GREEN
    AMP1 watchdog is GREEN
    AMP2 watchdog is GREEN
    PDWD watchdog is GREEN

PMC:
    It has been locked 3 days, 15 hr 20 minutes
    Reflected power = 23.37W
    Transmitted power = 104.4W
    PowerSum = 127.8W

FSS:
    It has been locked for 3 days 15 hr and 20 min
    TPD[V] = 0.6888V

ISS:
    The diffracted power is around 4.0%
    Last saturation event was 3 days 15 hours and 20 minutes ago


Possible Issues:
    PMC reflected power is high
    FSS TPD is low

LHO VE
jordan.vanosky@LIGO.ORG - posted 08:18, Monday 21 April 2025 (84017)
Morning Purge Air Checks 4-21-25

Morning dry air skid checks, water pump, kobelco, drying towers all nominal.

Dew point measurement at HAM1 , approx. -42C

Images attached to this report
H1 General
anthony.sanchez@LIGO.ORG - posted 07:50, Monday 21 April 2025 (84016)
Monday Ops Morning Shift Start

TITLE: 04/21 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
OUTGOING OPERATOR: None
CURRENT ENVIRONMENT:
    SEI_ENV state: MAINTENANCE
    Wind: 3mph Gusts, 1mph 3min avg
    Primary useism: 0.01 μm/s
    Secondary useism: 0.14 μm/s
QUICK SUMMARY:

VAC Team reports that the corner's pressure is currently 2e-6 Torr 

H1 AOS (AOS)
robert.schofield@LIGO.ORG - posted 17:03, Sunday 20 April 2025 (84015)
45 degree annular beam from BS reproduced in-chamber with flashlight; reminders of potential H1 scattering sites in H2 chambers

I made a couple of ancilliary investigations while I was in-chamber helping adjust CPY. First, I shined a flashlight through the ITMY elliptical baffle towards the BS. Figure 1 shows that this produced a 45 degree annular beam, similar to the one observed during lock that I noted here ( 83050 ) , consistent with the hypothesis that it is a reflection from the BS cage (see linked alog).

Second, our entry through BSC8 also reminded me that LHO has some unique potential scattering sites that LLO does not have.  Figure 2 shows that several of the blanked off nozzles in BSC8 act as corner retroreflectors visible to the beam spot on ITMY, and there is a reflection from the chamber, just below the beam.  A look at my compilation of beam spot photos from several years ago ( 41142-Figure3 ) also shows these issues at ITMX (second page of Fig. 2). We should probably put in nozzle baffles next time we are in-chamber near BSC8 and 7.

Non-image files attached to this report
H1 AOS (AOS, DetChar)
robert.schofield@LIGO.ORG - posted 16:51, Sunday 20 April 2025 (84014)
BS HEPI injection at 0.2 Hz increases noise in DARM

I recently reported on multiple potential stray light issues in the vertex area, including a 45 degree conical annular beam from the beamsplitter, and a reflection of the halo of the beam passing through the ITMX elliptical baffle that is roughly directed at ITMY (83050). In a first attempt to study potential scattered light noise problems from these beams, before the break I injected 0.2 Hz X and Y motion onto the BS HEPI, with motion amplitudes of about 1e-6 m at stages, 0 and 2 (see figure).  The figure demonstrates with spectrograms and spectra (second page), that there is a slight increase in DARM noise for both X and Y injections,  mainly below 60 Hz. I turned the injections on and off multiple times because the noise is pretty subtle. I think we should further study these potential scattering issues after the break.

Non-image files attached to this report
LHO VE
david.barker@LIGO.ORG - posted 10:12, Sunday 20 April 2025 (84013)
Sun CP1 Fill

Sun Apr 20 10:09:17 2025 INFO: Fill completed in 9min 14secs

 

Images attached to this report
H1 SUS (SEI)
brian.lantz@LIGO.ORG - posted 12:07, Saturday 19 April 2025 - last comment - 12:35, Wednesday 23 April 2025(84012)
OSEM estimator summary

Here's a quick summary of the Estimator installation from this week (Edgard, Oli, Jeff K, Brian L)

slides with basic info: T2500082 
FRS ticket 32526

Installation alogs
Infrastructure installed on HAM2/PR3 and HAM5/SR3, style updates to model, MEDM linked to sitemap - alog 83906

Tools installed in Estimator folder in the SUS SVN alog 83922

We updated the OSEM 10:0.4 calibration filters, but only on SR3 and PR3. alog 83913

Damping filters installed - alog 83926

Tested the fader switch - alog 83982

Designed and installed a blend for SR3 Yaw (DBL_notch in the first filter bank) - alog 84004

Created a new OSEM calibration script - alog 84005
(Edgard is thinking about a general version of this using Python, that is still TBD)

Fitting is well underway, but isn't done yet.

We made much more progress than we expected - thanks Oli and Jeff for all the help. It's not quite ready to go, we need to install the TF fits for the model.

We might have actually been able to test, except the temperature changes from the pumpdown were causing the SR3 optic to move, and the TFs were not very stable. Edgard is working on a log to document this. We have good fits for SR3 yaw taken Friday morning, and we might just try these remotely with Oli's help. We do plan to get a clean set of TFs in a few days when things have stabilized.

-- notes for next steps, thanks to Sheila for this --

We plan to leave the SR3 overall yaw damping gain at -0.5. This means we'll set the 'light damping' to -0.1  and the gain in the estimator to -0.4. Edgard used -0.1 for the fitting, but he notes that the Q's are pretty high so we may need to revisit this.

SR3 oplev channels are : H1:SUS-SR3_M3_OPLEV_{PIT,YAW}_OUT_DQ

Some interesting alogs about the impact of changes to SR damping: alog 72106 and 72130  

Elenna's PR3 coherence plots: alog 65495

 

Comments related to this report
brian.lantz@LIGO.ORG - 15:00, Monday 21 April 2025 (84029)

I've attached a quick spectrum of SR3 yaw and pitch on M3 as seen by the optical lever. It's odd - the yaw looks very lightly damped - but the IFO was in observe. You can not see real motion above the 3.4 ish Hz yaw mode (it should be falling faster that 1/f^6). You might be seeing real motion between the peaks though - and we can use that (peaks at 1, 2.3, 3.4).

(environment was pretty quiet - BLRMS - EQ is 40-100 nm/sec, microseism is 200-400 nm/sec, wind speed below 1 m/s, anthropogenic is 20-30 nm/sec. It's 3 pm Saturday afternoon, local time. )

I've added 2 more plots. The first is to check that the Y damping is on, and it seems to be. This is a spectrum of the Y osem signal. Ignoring seismic input (which is completely fair), the signal here should just be yaw_osem_noise * (1/1-G) (the minus sign assumes you get all the loop gain signs directly from the control). You can see dips at the resonances, so the loop is on, and has some gain, but not much at the 1 Hz mode, more at 3.4 ish Hz. I've also added my yaw noise reference from G2002065 - you can see here that the noise is a bit larger than my estimate above 1 Hz.

LDVW shows that the gain on the M1_DAMP_Y control was already turned down to -0.5 at this time.

Images attached to this comment
Non-image files attached to this comment
edgard.bonilla@LIGO.ORG - 12:35, Wednesday 23 April 2025 (84087)

Here is a comparison of the spectra of three channels that can be used to monitor the performance of the estimator. We compare the motion when the M0 Yaw damping loop gain is at -0.5, versus when it is at the -0.1 (which is what we are aiming for with the estimator). The equivalent estimator plots should look somewhere in between the purple and blue curves in the images attached.

- The first one is the OPLEV on SR3. If the estimator works, we should be able to see a difference on the mode Qs. The oplev should see that we are able to damp (or control) the modes to the same level as the -0.5 damping.

- The second one is the M1 OSEM spectrum. The closed loop spectrum dips at the resonances of the plant at -0.5 gain (because of the sensitivity function), so we should be able to see that the sensitivity (as seen by the OSEM) is different, but the OPLEV sees good control of the modes.

- The third one is the total drive on M1. We should see that the total drive around the resonances is similar to the drive we get with the -0.5 gain, but the total drive should decrease rapidly above 3 or so Hz. We will need a faster channel than the one shown in the last attachment.

 

The plan is to make a full list of channels to monitor in conversation with Oli and Jeff, then run a pilot test with the fits from 84041 later in the week.

Images attached to this comment
LHO VE
david.barker@LIGO.ORG - posted 10:12, Saturday 19 April 2025 (84011)
Sat CP1 Fill

Sat Apr 19 10:08:32 2025 INFO: Fill completed in 8min 29secs

 

Images attached to this report
H1 CDS
david.barker@LIGO.ORG - posted 08:51, Saturday 19 April 2025 - last comment - 09:26, Saturday 19 April 2025(84008)
h1susauxh2 crash Fri 18 April 2025 23:43:02 PDT

h1susauxh2 models stopped running 23:43:02 Fri 18apr2025 PDT with an ADC timing error.

I am able to ssh onto the machine and first scans suggest we have lost an ADC in this system (only 7 of 8 are seen with lspci). We will need to power cycle the IO Chassis before deciding if an ADC replacement is needed.

This is an auxiliary SUS frontend for HAM2 meaning ADCs only and no control function has been lost.

Dmesg:

[Fri Apr 18 23:43:12 2025] rts_cpu_isolator: LIGO code is done, calling regular shutdown code
[Fri Apr 18 23:43:12 2025] h1iopsusauxh2: ERROR - An ADC timeout error has been detected, waiting for an exit signal.
[Fri Apr 18 23:43:12 2025] h1susauxh2: ERROR - An ADC timeout error has been detected, waiting for an exit signal.
 

Images attached to this report
Comments related to this report
david.barker@LIGO.ORG - 09:15, Saturday 19 April 2025 (84009)

h1susauxh2 is running again, no hardware issues.

When opening an FRS ticket for this I found a similar one from 20 April 2019 (FRS12775) at which time a reboot of the computer fixed it. At 09:02 I stopped the models and powered down h1susauxh2 from command line. After a minute I powered it back up using IPMI. All 8 ADC cards are visible and the models started with no problems.

david.barker@LIGO.ORG - 09:26, Saturday 19 April 2025 (84010)

FRS for today's issue: FRS33903

H1 PSL (ISC)
ryan.short@LIGO.ORG - posted 16:45, Thursday 17 April 2025 - last comment - 10:57, Friday 25 April 2025(83989)
SPI Pick-off Path Install Day Three: Complete!

S. Koehlenbeck, J. Freed, J. Kissel, J. Oberling, R. Short

The SPI pick-off path installation on the H1 PSL table is now complete. The beam in the new SPI path has been reduced to 20mW and is currently being dumped with a razor dump between SPI-L1 and SPI-L2. Pictures attached reflect the final installation and layout, which will be be reflected in the updated as-built layout at a later date.

Associated entries: 83925, 83933, 83956, 83961, 83978, 83983 (and more to come)

Images attached to this report
Comments related to this report
jeffrey.kissel@LIGO.ORG - 15:28, Friday 18 April 2025 (83998)ISC, SQZ
ECR E2400083
IIET 30642
WP 12453

Here's Ryan's birdseye view labeled with all the components.
For details of the components, see the SPI BOM, T2300363, exported from its google sheets to -v4 as of this entry.
Images attached to this comment
corey.gray@LIGO.ORG - 09:53, Monday 21 April 2025 (84019)EPO

Tagging EPO for photos.

joshua.freed@LIGO.ORG - 10:57, Friday 25 April 2025 (84120)

83996 Power In ALS / SQZ / SPI Paths Post SPI Pick-off Install

H1 SUS (SUS)
rahul.kumar@LIGO.ORG - posted 15:45, Thursday 17 April 2025 - last comment - 10:00, Monday 21 April 2025(83984)
Prep work for HAM1 SUS Tip Tilt (RM1, RM2 and PM1) installation

RyanC, Rahul

SUS Tip Tilt - RM1, RM2 and PM1 (picture attached) are now ready to be installed into HAM1, once the chamber is ready to accept them. The blade springs of all three suspensions have been un-muted and bosem connectors have kapton take inserted to prevent grounding issues. This morning we cleaned all three optics using First Contact - see picture for reference.

 

PM1 Beam Dump (rear)

Camilla, Betsy, RyanC, Rahul

SUS PM1 (Tip Tilt) has a new beam dump attached to it's rear - as shown in several pictures attached below. We had to design a new plate (D2500101_V1) to attach the beam dump. I can confirm that all the components integrates well with PM1 and there is some scope for adjustability as well.

Team SUS is now ready for HAM1 installation work.

Images attached to this report
Comments related to this report
corey.gray@LIGO.ORG - 10:00, Monday 21 April 2025 (84020)EPO

Tagging EPO for photos.

H1 PSL (ISC, PSL)
sina.koehlenbeck@LIGO.ORG - posted 15:36, Thursday 17 April 2025 - last comment - 11:44, Monday 21 April 2025(83983)
Install SPI pick-off path: Laser mode to fiber collimator

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:

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 %.

Images attached to this report
Comments related to this report
jeffrey.kissel@LIGO.ORG - 10:35, Friday 18 April 2025 (83995)ISC, SEI, SQZ, SYS
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%
sina.koehlenbeck@LIGO.ORG - 11:44, Monday 21 April 2025 (84025)

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.

Images attached to this comment
H1 PSL
jeffrey.kissel@LIGO.ORG - posted 16:03, Wednesday 16 April 2025 - last comment - 11:35, Monday 21 April 2025(83961)
SPi Pickoff Path Install Day Two
J. Kissel scribing for S. Koehlenbeck, J. Oberling, R. Short, J. Freed
ECR E2400083
IIET 30642
WP 12453

Another quick summary aLOG at the end of the day, with more details to come:
- With the power in the ALS/SQZ pick-off path to 10 [mW] for beam profiling,
- Installed a two lens system to handle the unexpectedly different beam profile of the ALS/SQZ pick-off path
- Remeasured the resulting mode after the two lens system, and we're happy enough. We're gunna call them SPI-L1 and SPI-L2.
- Installed steering mirrors SPI-M1 and SPI-M2.
- Rotated ALS-HWP2 to increase the s-pol light in the ALS/SQZ/SPI path to return the power transmitted through SPI-BS1 going to the ALS/SQZ fiber collimator back to 50.5 [mW]. This set the SPI path to 186 [mW] with the PMC TRANS measured at 103.5 [W]. The ALS_EXTERNAL PD in transmission of ALS-M9 measured 31 [mW] ***. 
- Installed SPI-HWP1 and SPI-PBS01
- Measured the power at each port of SPI-PBS01, with the intent to optimize the SPI-HWP1 position to yield maximum p-pol transmission through SPI-PBS01.

*** We expect this is lower than the goal of ~45 [mW] (from LHO:83927) because we've not yet re-aligned the ALS/SQZ fiber collimator path after the install of the SPI-BS1, which translates the beam a bit due to the thickness of the beam splitter. We intend to get back to this once we're happy with the SPI path.
Comments related to this report
ryan.short@LIGO.ORG - 17:54, Wednesday 16 April 2025 (83965)

Small correction to above is after installing SPI-HWP1 and SPI-PBS01, we adjusted HWP1 to have 20mW in transmission of PBS1 (not maximum quite yet) to start alignment into the fiber. Using the two steering mirrors downstream of PBS1 and the collimating lens in front of the fiber, Sina maximized the transmission as measured with the output of the fiber on a spare PD. We then took power measurements of the input and output of the fiber:

  • Input: 19.4mW
  • Output: 13.5mW
  • Transmission ratio: 72.1%

This is a good start, but with a target ratio of >80%, there's still more work to be done here improving the beam into the fiber collimator. Out current mode-matching solution claims we should have 95% mode overlap into the fiber, so hopefully the issue is alignment, but it's entirely possible we'll revisit the mode-matching to see if improvements can be made there too.

The attached photo represents the optical layout as it stands as of where we stopped today, with the new SPI fiber in blue on the left (north) side of the table.

Images attached to this comment
jeffrey.kissel@LIGO.ORG - 12:10, Thursday 17 April 2025 (83976)ISC, SQZ, SYS
Re-post of Ryan's picture at the end of day 2, labeled with the almost entirely complete SPI pick-off path.

Critically here, this shows the PSL row/column grid, confirming that this whole ECR E1900246 ALS pick-off path is 2 rows "higher" in +Y than is indicated on the current version of the as built PSL drawing D1300348-v8.
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jeffrey.kissel@LIGO.ORG - 11:35, Monday 21 April 2025 (84024)
Ryan grabbed another picture I attach here. This shows the ALS pick-off path on this day in order to support the identification that the beamline between ALS-M1, through the faraday ALS-FI1 and ALS-L1, etc stopping at ALS-M2 (not pictured) is on row 25 of the PSL table *not* row 23 as drawn in D1300348-v8. I attach both the raw picture and my labeled version. So, ya, ALS-M1 should have its HR surface centered on Row 25, Col 117.

Note, the grid in the picture is labeling bolt holes. Because the optical elements are all ~4 inches above the table, the beams appear offset from the way they travel on along the grid given that the photo was taken at a bit of an angle from vertical. May the future updater of D1300348 bear this in mind.

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H1 PSL (ISC, SQZ, SYS)
jeffrey.kissel@LIGO.ORG - posted 14:15, Wednesday 16 April 2025 - last comment - 11:36, Monday 21 April 2025(83956)
Beam Profiling the ALS / SQZ Fiber Distribution Pick-off Path in Prep for SPI Pick-off
J. Kissel scribing for S. Koehlenbeck, R. Short, J. Oberling, and J. Freed
ECR E2400083
IIET 30642
WP 12453

During yesterday's initial work installing the SPI pick-off path (LHO:83933), the first optic placed was SPI-BS1, the 80R/20T power beam-splitter that reflects most of the s-pol light towards the new SPI path. The pick-off is to eventually be sent into a SuK fiber collimator (60FC-SF-4-A6.2S-03), so we wanted to validate the beam profile / mode shape of this reflected beam.


The without changing any power in the ALS/SQZ/SPI pick-off path, the power now reflected from newly installed SPI-BS1 measured ~40 [mW] (see LHO:83946). This is too much for the WinCam beam profiler, so they used ALS-HWP2 to rotate the polarization going into ALS-PBS01, and thus reduced the reflected s-pol light in this ALS/SQZ/SPI pick-off path to ~10 [mW]. That necessarily means there's a little more of the ~2 [W] p-pol light transmitted and going toward the HAM1 light pipe, so they placed a temporary beam dump after ALS-M2 so as to not have to think about it.

The they set up a WinCam head on a rail and gathered the beam profile. With the WinCam analysis software on a computer stuck in the PSL, they simply gathered the profile information which I report here: 
# Distance[cm]	Radius[um]   Radius[um]
                   X             Y
    0.0           680.5         717
    17.78         465           504
    25.4          389           428.5
    30.48         346.5         368
    38.1          281.5         300.5

where "X" is parallel to the table, and "Y" is orthogonal to the table. The "0.0" position in this measurement is the "front" of the rail (the right most position as pictured in the attachment), which is Column 159 of the PSL grid. SPI-BS1 has the center of its reflective surface is set in +/- X position in Column 149 (within the existing ALS-PBS01 to ALS-M9 beam line). It's +/- Y position is set to create a reflected beam line along Row 30 of the grid, and the WinCam head and rail are centered in +/- Y on that Row to capture that beam.

Using this profile measurement, we find it to be quite different than expected from when this path was installed circa 2019 (see e.g. LHO:52381, LHO:52292, LHO:51610). Jason shared his mode matching solution from LHO:52292 with us prior to this week, and I've posted it as a comment to that aLOG, see LHO:83957.

We think we can trace the issue down to an error in the as-build drawing for the PSL:
- the whole beam path running in the +/-X direction from ALS-M1 to ALS-M2 is diagrammed to be on row 23 -- however, we find in reality, the path lies on row 25. That's 2 inches more between the (unlabeld) pick-off beam splitter just prior to ALS-M1 and ALS-M1 itself. Easily enough to distort a mode matching simulation.
- Jason confirms that he used the *drawing* to design the lens telescope for this ALS/SQZ fiber distribution pick-off path.

More on this as we work through a lens solution for the SPI path.

As of this entry, we elect to NOT create a new solution for the whole ALS/SQZ fiber distribution pick-off i.e. we *won't* adjust ALS-L1 or ALS-L5 in order to fix the true problem. But, we report what we found in the event that a case is better made to help mode matching and aligning into the ALS/SQZ fiber distribution pick-off easier -- as we have verbal confirmation that it was quite a pain.
For the record the fiber collimator used in the ALS/SQZ distribution pick-off is a Thor Labs F220 APC-1064.
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Comments related to this report
jeffrey.kissel@LIGO.ORG - 14:32, Wednesday 16 April 2025 (83960)
Just a quick trend of the SM1PD1A EXTERNAL PD in transmission of ALS-M9 after they throttled the s-pol power in the ALS/SQZ/SPI path to ~10 [mW]. 
In that trend, you can see the different in "lights on" vs. "lights off" highlighted with the magenta vertical lines.

Note, as you can see in the picture, the reflection of ALS-M9 is dumped so as to not have to think about how much power is or is not going into the ALS/SQZ fiber distribution collimator (ALS-FC2), so the INTERNAL monitor PD that's in the distribution chassis itself is "correctly" unexpectedly reading nothing, so I don't show it.
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jeffrey.kissel@LIGO.ORG - 08:23, Friday 18 April 2025 (83993)
Correction to the last sentence of the main entry -- the ALS/SQZ fiber collimator is *not* an, but instead a Thorlabs Fiber Port PAF2-5A, pictured well in FinalInstall_ALSfiber.jpg from LHO:83989.

I had incorrectly assumed that this collimator would be a copy of ALS-FC1, which *is* listed in E1300483 as an F220 APC-1064.
sina.koehlenbeck@LIGO.ORG - 11:36, Monday 21 April 2025 (84023)

In the attachment you will find the fit with JAMMT to the measured beam profile data with offset correction:

  • Offset of measurement point to SPI-BS1: 10.2 cm
  • Offset of measurement point to beam profiler surface: 7.3 cm
Distance (cm) Radius horiz. (um) Radius vert. (um)
17.46 680.5 717
35.24 465 504
42.86 389 428.5
47.94 346.5 368
55.56 281.5 300.5
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