Ops Eve Shift Start

TITLE: 08/13 Eve Shift: 2330-0500 UTC (1630-2200 PST), all times posted in UTC
STATE of H1: Observing at 150Mpc
OUTGOING OPERATOR: Oli
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 22mph Gusts, 11mph 3min avg
    Primary useism: 0.05 μm/s
    Secondary useism: 0.11 μm/s
QUICK SUMMARY: Windy, smokey, and hot afternoon on site, but so far H1 has been locked for 8.5 hours following commissioning time this morning.

• Wind moderate with gusts over 20mph
• All other systems nominal

PSAMS (for HxDS with a Piezo-SAMS payload) assembly and characterization at CIT for O5

Camille Makarem (CIT), Rahul

Last week at CIT we assembled and tested four units of PSAMS (Piezo-SAMS payload - Piezo-deformable Mirrors for Active Mode Matching). These four fully assembled PSAMS are shown in attachment01 and attachment02 and they will be shipped to LLO for O5 HPDS assembly and installation in HAM6. Given below are the test results of the PSAMS payload - PZT actuation and the desired radius of curvature of the mirror at 100V.

1. Optic  E2100053, Type A2, s/n - 02 - PZT voltage tested from 0 to 200V, Pre-load set to 32 in. lbs at 100V DC, RoC = 2.42 m

2. Optic E2100053, Type A1, s/n - 01 - PZT voltage tested from 0 to 200V, Pre-load set to 32 in. lbs at 100V DC, RoC = 5.76 m

3. Optic E2100053, Type B2, s/n - 01 - PZT voltage tested from 0 to 200V, Pre-load set to 30 in. lbs at 100V DC, RoC = 2.41 m

4. Optic E2100053, Type B1, s/n - 03 - PZT voltage tested from 0 to 200V, Pre-load set to 28 in. lbs at 100V DC, RoC = 5.63 m

The Strain gauge readout results will be posted later on. 

PSAMS assembly details and issues (faced) are discussed below,

a.  Attachment03 shows the PZT with five lead wires. We looked into the vendor data to identify + HV PZT (the side which has been marked with dots) and PZT ground (non dotted side). The other 3 leads belong to the Strain Gauge (SG). We crimped pins to all five leads - as shown in attachment04. The wire pins were then pushed into the 7 pin Glenair might mouse connector (MM 803-003-02M6-7PN-598A) - as shown in attachment05. We also used a PEEK zip tie to secure the wires on the PZT stack. We followed D2000383 for the wiring chain diagram.  

b. During the assembly we did not have vendor data to identify the leads for the strain gauge, hence we connected the wires based on the spare units at CIT (which lead to some confusion as the two spare units internal wiring contradicted each other). As per D2000382, the bridge excitation should be connected to pin 1 on the might mouse connector and GND should be at pin 3, strain signal on pin 6. In reality we connected the GND to pin1, strain signal to pin6 and +V bridge excitation to pin 3 (basically pin 1 and pin 3 are inverted).  Later (post assembly), Camille acquired the vendor data for identifying the leads for the strain gauge, which is shown here. After discussing this with Jeff Kissel and Daniel, we concluded that this should not affect the working of the SG - however for future assembly we should use the latest vendor data.

c. The PZTs, washers and the deformable mirror were all stacked vertically (as per T2400260) and torqued as per specification - see pictures for reference here - attachment05, attachment06, attachment07, attachment08 and full assembly shown in attachment09.

d. Electrical testing - we followed E2100371 to confirm the electrical connections for the PZT voltage and strain gauge readout - test set up shown in attachment10 and attachment11.

e. RoC measurement on ZYGO interferometer - after successfully testing and confirming the working of the PZT actuation we started measuring the Radius of Curvature (RoC) of the optic on the ZYGO interferometer - see attachment12, attachment13 and attachment14 for details of the setup - fringes observed as shown here, as an example. The final numbers (pre-load and the RoC for each mirror) are posted above.

We wanted to capture few things which we faced during the assembly and testing and this will help for assembling future units. These are listed below,

1. Tangless helicoils for mirror mounting - we used tanged helicoils for mirror mounting, however breaking the tang after the assembly was very unsafe for the mirror. Hence, we had to unmount the mirror from the flexure mirror holder, break the tangs and then re-mount the mirror (which involves heating and cooling them). Hence, we would recommend to use tangless helicoils only.

2. We struggled to attach D1900097 to D1900123 since the threads were bad on D1900097. Don got us a 1''-32 size tap from McMaster to chase the threads, however I could only chase a few of them - enough to assemble four units. The threads on the other 6 units (D1900097) at CIT were extremely difficult to chase hence we included it in our future to-do list of things (might have to be made dirty again for proper chasing).

3. PEEK zip tie for wire lacing inside the PSAMS - the old PSAMS used viton ring to lace the PZT electrical leads, this has now been replaced with PEEK zip tie. We were not very convinced with this, as the viton ring felt easier to use and more secure for the wires.

4.  We spent a lot of time trying to understand and interpret the correct wiring diagram - initially Fabrice's FDR and Luis's document contradicted each other. To add to the confusion, the already built unit at CIT (two spare psams, with two different cables and might mouse connections) wiring also contradicted each other. However (long story short), after talking to Fil and Marc at LHO we were able to sort it. We had to change the 18V power supply to the PZT driver D2000555, since the exciting one was faulty. Also, Dean (at CIT) made some quick checks on the PZT driver to confirm that it was healthy. However the most important thing to note over here is as follows - the two spare units at CIT, ZM2 and ZM5 (from the previous build) have wiring diagrams different from the design (I think for ZM2), hence this needs to be checked before future use. 

Camille as noted down the serial number of the parts used during this assembly and they are listed here.

DRMI locking histograms Pre & Post ReflAir changes

5 day increments.
I chose 5 days before June 16th because on June 16th there was a ReflAir Phase change, and 5 days later there was another change to ReflAir phasing.
So given a window of 5 days in between 2 changes I chose 5 days before, 5 days between changes, and DRMI after the last change for 5 days.

ZM4 Strain Gauge Minimum Value Slightly Drifting

Leo, Camilla

Leo noticed when comparing the data we took in July 85917 to last years OMC scans with different ZM curvature settings 80010, that the minimum value ZM4 can reach has changed. Over ~ an hour or so, the strain gauge can drift around 0.1V, their total ranges are 7.7V so maybe these changes of 0.2/7.7=2.5% are not too surprising.

• In September 2024, 0V on ZM4 was a strain gauge of 2.1V. Drifted to 2.05V after 2 hours.
• In December 2024, 0V on ZM4 was 2.15V and 0V on ZM5 was -5.40V. 185V was 9.25 on ZM4 and 1.95 on ZM5.
• In July 2025, 0V on ZM4 was 2.3V and 0V on ZM5 was -5.45V. 195V was 10 on ZM4 and 2.35 on ZM5

H1 dust monitor Month-Long Trends FAMIS

Closes FAMIS37255, last checked in alog85779

Everything looks as expected, LVEA5 is off during observing.

H1 PSL Status Report Weekly FAMIS

Closes FAMIS26544, last checked in alog86165
Laser Status:
    NPRO output power is 1.86W
    AMP1 output power is 70.07W
    AMP2 output power is 140.6W
    NPRO watchdog is GREEN
    AMP1 watchdog is GREEN
    AMP2 watchdog is GREEN
    PDWD watchdog is GREEN

PMC:
    It has been locked 1 days, 2 hr 21 minutes
    Reflected power = 23.57W
    Transmitted power = 105.3W
    PowerSum = 128.9W

FSS:
    It has been locked for 0 days 5 hr and 47 min
    TPD[V] = 0.8582V

ISS:
    The diffracted power is around 4.1%
    Last saturation event was 0 days 5 hours and 48 minutes ago

Possible Issues:
    PMC reflected power continues to be high, we can see a drop during the Tuesday incursion work, but it has risen a bit since then.

Calibration measurements at three ESD biases

Today, we measured the calibration at three different ESD biases. First, we measured at the current bias of 269 V, and then our O4 standard bias of 136 V. Then, I stepped up to a higher bias of 409 V.

ESDAMON value	Bias Offset	L3 Drivealign gain	Calibration report	Notes
269 V	6.0542453	88.28457	alog: 86337 report: 20250813T153848Z	only 1 hour thermalized at measurement time current operating bias
136 V	3.25	198.6643	alog: 86339 report: 20250813T162026Z	nominal O4 bias, calibration model fit at this bias
409 V	8.89	57.587	alog: 86341 report: 20250813T174921Z	ESD saturation warnings while at this bias Took 5 minutes of quiet time, cal lines on, at this new bias start: 18:12:54 UTC end: 18:18:00 UTC

The attached plot compares the three broadband measurements at each ESD bias. It seems like the overall systematic error decreases as we increase the ESD bias.

To step up the ESD bias, I used guardian code that Sheila attached to this alog. Another relevant alog comparing simulines results at different biases is here.

BTRP adapter flange and GV installed at MY

Similar to alog 86227, the BTRP adapter flange and GV were installed on Tuesday at the MY station.  Leak checking was completed today with no signal seen above the ~e-12 torrL/s background of the leak detector.  

Pumping on this volume will continue until next Tuesday, so some additional noise may be seen by DetChar.  This volume is valved out of the main volume, so the pressure readings from the PT-243 gauges can be ignored until further notice.  

Here are the first and the last pictures of the leak detector values.
The max was 3.5 * 10-12. 90% of the time it stayed at <1 *10-12.

The pumping cart was switched off, and the dead volume was valved back in to the main volume. The pressure dropped rapidly to ~5E-9 within a few minutes, and it continues to drop.

Also, we (Travis & Janos) added some more parts (an 8" CF to 6" CF tee; CF to ISO adapters, and an ISO valve) to the assembly, and also added a Unistrut support to the tee; see attached photo. Next step is to add the booster pump itself, and anchor it to the ground.

LOTO was applied now both to the handlers of the hand angle valve and the hand Gate Valve.

Calibration Measurement August 13, 2025 17:42 UTC

At the time of starting these measurements, we had been Locked for over 3 hours, so we were fully thermalized
CALIBRATION_MONITOR screen and pydarm report are attached

Broadband
2025-08-13 17:42:30 - 17:47:47 UTC
/ligo/groups/cal/H1/measurements/PCALY2DARM_BB/PCALY2DARM_BB_20250813T174237Z.xml

Simulines
2025-08-13 17:48:52 - 18:12:09 UTC
/ligo/groups/cal/H1/measurements/DARMOLG_SS/DARMOLG_SS_20250813T174853Z.hdf5
/ligo/groups/cal/H1/measurements/PCALY2DARM_SS/PCALY2DARM_SS_20250813T174853Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L1_SS/SUSETMX_L1_SS_20250813T174853Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L2_SS/SUSETMX_L2_SS_20250813T174853Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L3_SS/SUSETMX_L3_SS_20250813T174853Z.hdf5

Wed CP1 Fill

Wed Aug 13 10:07:22 2025 INFO: Fill completed in 7min 18secs

Gerardo confirmed a good fill curbside.

Calibration Measurement August 13, 2025 16:13 UTC

At the time of starting these measurements, we had only been Locked for 1.5 hours, so we were not fully thermalized
CALIBRATION_MONITOR screen and pydarm report are attached

Broadband
2025-08-13 16:13:34 - 16:18:45 UTC
/ligo/groups/cal/H1/measurements/PCALY2DARM_BB/PCALY2DARM_BB_20250813T161334Z.xml

Simulines
2025-08-13 16:19:57 - 16:43:04 UTC
/ligo/groups/cal/H1/measurements/DARMOLG_SS/DARMOLG_SS_20250813T161958Z.hdf5
/ligo/groups/cal/H1/measurements/PCALY2DARM_SS/PCALY2DARM_SS_20250813T161958Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L1_SS/SUSETMX_L1_SS_20250813T161958Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L2_SS/SUSETMX_L2_SS_20250813T161958Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L3_SS/SUSETMX_L3_SS_20250813T161958Z.hdf5

Calibration Measurement August 13, 2025 15:30 UTC

At the time of starting these measurements, we had only been Locked for 1 hour (1hr10min since MAX_POWER), so we were not fully thermalized
CALIBRATION_MONITOR screen and pydarm report are attached

Broadband
2025-08-13 15:31:30 - 15:37:02 UTC
/ligo/groups/cal/H1/measurements/PCALY2DARM_BB/PCALY2DARM_BB_20250813T153151Z.xml

Simulines
2025-08-13 15:38:19 - 16:01:22 UTC
/ligo/groups/cal/H1/measurements/DARMOLG_SS/DARMOLG_SS_20250813T153820Z.hdf5
/ligo/groups/cal/H1/measurements/PCALY2DARM_SS/PCALY2DARM_SS_20250813T153820Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L1_SS/SUSETMX_L1_SS_20250813T153820Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L2_SS/SUSETMX_L2_SS_20250813T153820Z.hdf5
/ligo/groups/cal/H1/measurements/SUSETMX_L3_SS/SUSETMX_L3_SS_20250813T153820Z.hdf5

Ops Day Shift Start

TITLE: 08/13 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Observing at 151Mpc
OUTGOING OPERATOR: Tony
CURRENT ENVIRONMENT:
    SEI_ENV state: CALM
    Wind: 3mph Gusts, 0mph 3min avg
    Primary useism: 0.02 μm/s
    Secondary useism: 0.12 μm/s
QUICK SUMMARY:

Currently Observing at 153 Mpc and have been Locked for 10 minutes

CDS Maintenance Summary: Tuesday 12th August 2025

WP12746 h1omc0 Low Noise ADC Autocal Test

EJ, Jonathan, Dave:

For a first test we restarted h1iopomc0 three times to run an autocal on the low-noise ADC -- each time the autocal Failed. Next test will be to power cycle existing card leading to possible replacement.

WP12755 TW1 Raw Minute Trend Offload

Dave:

h1daqtw1 was configured to write it raw minutes into a new local directory to isolate the last 6 months of data from the running system. The NDS service on h1daqnds1 was restarted to serve these data from this location while the file transfer progresses.

Restarts

Tue12Aug2025
LOC TIME HOSTNAME     MODEL/REBOOT
09:06:26 h1omc0       h1iopomc0   <<< three ADC AUTOCAL tests
09:08:12 h1omc0       h1iopomc0   
09:08:58 h1omc0       h1iopomc0   
09:09:12 h1omc0       h1omc       <<< start user models
09:09:26 h1omc0       h1omcpi     
11:51:19 h1daqnds1    [DAQ] <<< reconfigure for TW1 offload
 

BTRP adapter flange and GV installed at MX

Yesterday, we installed the BTRP (Beam Tube Roughing Pump) adapter flange on the 13.25" gate valve just to the -X side of GV13.  This included installing a 8" GV onto the roughing pump port of the adapter, moving the existing gauge tree onto the new adapter, and installing a 2.75" blank on an unused port.  All of the new CF joints were helium leak tested and no signal was seen above the ~9e-11 torrL/s background of the leak detector. 

The assembly is currently valved out of the BT vacuum volume via the 13.25" GV, and is being pumped down via small turbo and aux cart.  Therefore, the PT-343 gauge reading is only reporting on the BTRP assembly pressure, not the main BT pressure, so it can be ignored until further notice of it being vavled back in.  This system has been pumping via aux cart or leak detector since ~2pm yesterday, and will continue to be pumped until it is in the pressure range of the BT volume.  The aux cart is isolated by foam under the wheels, but some noise may be noticed by DetChar folks, hence the DetChar tag on this report.

A before - after pair of photos.
As the conductance is very bad in this complex volume, we're aiming to pump it until next Tuesday. The estimated pressure rise of the main volume after valving in this small volume next Tuesday is less than E-12 Torr (after equalizing) - in other words, negligible.

Some backstage snapshots of the great teamwork of Travis, Janos, and me on installing these: Pic. 1 - "before"; 2,3 - 90% complete.

LOTO was applied now both to the handlers of the hand angle valve and the hand Gate Valve.
Also, components have been added to the header, only 1 piece away from the booster pump.

Lockloss from NLN

3:47:39 UTC unknown Lockloss  

 

Optical Setup and Results of first tuning of SPI In-vac SuK Fiber Collimator Lens Position

J. Kissel

Executive Summary
I've tuned the lens position and measured the projected beam profile of one of three trial fiber collimators to be used for the SPI. The intent is to do this measurement before vs. after a vacuum bake like done for previous collimators (Section 3.3 of E1500384), to see if the bake will cause any negative impact on the performance of the collimator. It also helped clear out a few "rookie mistake" bugs in my data analysis, though there's still a bit of inconsequential confusion in post-processing the fit of the beam profile.

Full Context
The SPI intends to use supposedly vacuum compatible Schaefter + Kirchhoff (SuK) fiber collimators (D2500094, 60FC-0-A11-03-Ti) in order to launch its two measurement (MEAS) and reference (REF) beams from their fiber optical patchcords attached to feedthroughs (D2500175) in to free-space and throughout the ISIK transceiver / interferometer (D2400107). However, unlike their (more expensive) stainless steel counterparts from MicroSense / LightPath used by the SQZ team, SuK doesn't have the facilities to specify a temperature at which they believe the titanium + D-ZK3 glass lens + CuBe & Ti lens retaining ring assembly will fail (see E2300454). As such, we're going to run one SuK collimator through the same baking procedure as the MicroSense / LightPath (see Section 3.3 of E1500384) -- slow 6 [hr] ramp up to 85 [deg C], hold for 24 hours, similar slow ramp down -- and see if it survives.

A catastrophic "if it survived" result would be that the lens cracks under the stress of differential heating between the titanium, CuBe, and glass. 
As we don't expect this type of failure, in order to characterize "if it still functions," we want a quantitative "before" vs "after" metric. 
Since I have to learn how to "collimate" this type of collimator anyways (where "collimate" = mechanically tune the lens position such that emanating beam's waist is positioned as close to the lens as possible), I figure we use a 2D beam profile as our quantitative metric. We expect the symptom of a "failed" fiber collimator to be that "before bake it projects a lovely, symmetric, tunable, Gaussian beam, and after bake the profile looks asymmetric / astigmatic or the lens position is no longer consistently/freely adjustable."

The SPI design requires a beam whose waist (1/e^2) radius is w0 = 1.050 mm +/- 0.1 mm. That puts the Rayleigh range at zR = pi (w0^2) / lambda =  3.25 [m], so in order to get a good fit on where the waist lies, we need a least one or two data points beyond the Rayleigh range. So that means projecting the beam over a large distance, say at least ~5-6 [m].

Measurement Details
2025-06-03_SPIFC_OpticalSetup.pdf shows the optical setup. 

Pretty simple; just consuming a lot of optical table space (which we thankfully have at the moment). The "back" optical table (in IFO coordinates the "-X table (with the long direction oriented in the Y direction") already has a pre-existing fiber coupled, 1064 nm, laser capable of delivering variable power of least 100 [mW] so I started with that. It's output has an FC/APC "angled physical contact" connector, where as the SuK fiber collimators have an FC/PC (flat) "physical contact" connector. I thus used a ThorLabs P5-980PM-FC-2 APC to PC fiber patch cord to couple to the SuK fiber collimator, assembled with a (12 mm)-to-(1 inch) optic mount adapter (AD12NT) and mounted in a standard 1" mirror mount, set at 5 inch beam height. Ensuring I positioned the free-space face of the collimator at the 0 [in] position, I projected to beam down the width of the optical table, placed steering mirrors at 9 [ft] 9 [in] (the maximum +Y grid holes), separated by 6 [in] in order to return the beam down the table. Along this beam, I marked out grid-hole positions to measure the beam profile with a NanoScan head at 
    z = [0.508 0.991 1.499 2.007 3.251 4.496 5.41] [m] 
These are roughly even half-meter points that one gets from "finding 1 inch hole position that gets you close to 0.5 [m] increments", i.e. 
    z = [1'8", 3'3", 4'11", 6'7", 10'8", 14'9", and 17'9"].

Using the SuK proprietary tooling, I then loosened the set-screws that had secured the lens in position with the 1.2 mm flat-head (9D-12), and adjusted the position of the lens with their short eccentric key (60EX-4), per their user manual (T2500062 == Adjustment_60FC.pdf), with the NanoScan was positioned at the 5.41 [m] position.
At the 5.41 [m] position, we expect the beam radii to be w(z=5.41 m) = w0 * sqrt(1 + (z/zR)^2) = 2.036 [mm], or a beam diameter of d(z=5.41 m) = 4.072 [mm].

Regretfully, I made the rookie mistake of interpreting the NanoScan's beam widths (diameters) as radii on the fly, and "could not get a beam 'radii' lower than 3.0 [mm]," at the z = 5.41 position, as adjustments to the eccentric key / lens position approached a "just breath near it and it'll get larger" level at that beam size. This will be totally fine for "the real collimation" process, as beam widths (diameters) of 4.0 [mm] required much less a delicate touch and where quite repeatable (I found, while struggling to achieve 3.0 [mm] width).

Regardless, once I said "good enough" at the lens position, I re-secured the set screws holding the lens in place. That produced a d = 3.4 [mm] beam diameter, or 1.7 [mm] radius, at the z = 5.41 [m]. I then moved the NanoScan head to the remaining locations (aligning the beam into the head at each position, as needed, with either the steering mirrors or the fiber collimator itself) to measure the rest of the beam profile as a function of distance.

2025-06-03_SPIFC_BeamScans_vs_Position.pdf shows the NanoScan head position and raw data at each z position after I tuned the lens position at z = 5.41 [m].
Having understood during the data analysis that the NanoScan software returns either 1/e^2 or D4sigma beam *diameters*, I followed modern convention and used the mean D4sigma values, and converted to radii with the factor of 2, w(z) = d(z) / 2. One can see from the raw data that the beam profile at each point is quite near ''excellently Gaussian,'' which is what we hope will remain true *after* the bake.

Results

2025-06-03_spifc_S0272502_prebake_beamprofile_fit.pdf shows the output of the attached script spifc_beamprofile_S0272502_prebake_20250603.m, which uses Sheila's copy of a la mode to fit the profile of the beam.

Discussion
The data show a pretty darn symmetric beam in X (parallel to the table) and Y (perpendicular to the table), reflecting what had already been seen in the raw profiles.
The fit predicts a waist w0 of 
        (w0x, w0y) = (0.89576, 0.90912) [mm] 
at position 
        (z0x, z0y) = (1.4017, 1.3469) [m] 
away, downstream from the lens. Makes total sense that the z position of the waist is *not* at the lens position, given that I tried to get the beam as small a *diameter* possible at the 5.41 [mm] position, rather than what I should have done which is to tune the lens position / beam diameter to be the desired 4.072 [mm].

What doesn't make sense to me, is that -- in trying to validate the fit and/or show that the beam behaves as an ideal Gaussian beam would -- I also plot the predicted beam radius at the Rayleigh range, 
    w(zR) [model] = w0 * sqrt(1 + (zR/zR)^2) = w0 * sqrt(2),
or 
         (wzRx, wzRy) [model] = (1.2668,1.2857) [mm]
which is much larger than the fit predicts,
         (wzRx, wzRy) [fit] = (0.9677,0.9958) [mm]
at a Rayleigh range,
    zR = pi * w0^2 / lambda
of 
         (zRx,zRy) [from fit w0] = (2.3691, 2.4404) [m]

Similarly confusing, if I plot a line from the waist position (z0x, z0y) to the end of the position vector (6 [m]), whose angle from the x-axis is the divergence angle
    theta_R = lambda / (pi * w0)
i.e. a predicting a waist radius at zEnd = 6 [m] of 
    w(zEnd) = (zEnd - z0) * atan(theta_R)
this results in a beam waist at xEnd much smaller than the fit. Most demo plots, e.g. from wikipedia:Rayleigh_length or wikipedia:Beam_divergence, show that slope of the line should start to match the beam profile just after the Rayleigh range. To be fair, these demos never have quantitative axes, but still. At least the slope seems to match, even though the line is quite offset from the measured / fit z > 6 [m] asymtote.

Conclusion
Though I did not adjust the lens position to place the beam waist at desired position, I now have a good measurement setup and data processing regime to do so for the "production" pair of fiber collimators. For this collimator, since we're just looking at "before" vs. "after" bake data, this data set is good enough.

Let's bake!

I took a moment to revisit the "cross checks" of the fit -- namely why the waist at the Rayleigh range (w(zR)) and Divergence angle's (\theta_{R}) prediction of what the waist should be in the "far field," (w(zEnd)), and solved the "mysteries."

(1) For the the prediction of the waist radius at the Rayleigh range: all the above math was correct, it's merely that I did not properly offset the z position w.r.t. where the origin of the plot lie (at the fiber collimator). If I adjust the z position for that offset
    (zRx,zRy) [from fit w0] = (z0x+zRx, z0y+zRy) [from fiber collimator, i.e. z = 0 [m]] 
                            = (1.4017, 1.3469) + (2.3691, 2.4404) [m]
                            = (3.7708, 3.7899) [m]
then the waist radius (w0 * sqrt(2)) lands bang-on the fit and measurement.

(2) For why the simplistic model of divergence angle doesn't appear to match the divergence of the measurements or model: this is merely a question of what really is "near" and "far" field. Turns out if you just expand the z range what I would call "way" out -- from 6 [m] to 20 [m] -- you see convergence between the two models.

The pdf attached here is a new version of the plots showing the same data and model above, but with the simplistic models fixed. I now show two pages, page one with the original zoom from z = 0 to 6 [m] aka the "Near" field demonstrating (1), and page two zoomed out from z = 0 to 20 [m] demonstrating (2).

I also attach the updated version of the code, spifc_beamprofile_S0272502_prebake_20250603.m.