S. Muusse, C. Compton, G. Valente

Alignment of 4.65um beam on the ITMY was completed, excluding the QPD optics which require reflection off the ITM. I've attached a picture of the almost complete table with the notable optics modified today indicated. I'll get someone taller to add a better picture in the comments of the whole table.

• All the PD optics were placed and aligned (another picture).
• The PD electronics (x-arm Chassis & PD power supply) were temporarily installed and slow and monitor channels were shown to be operational.
• Thermal pickoff aligned.
• The beam dump flipper orientation has been problematic but has been solved by dumping when the flipper is vertical and placing the beam dump at a ≈ 30deg angle (picture attached).

Next steps:

• Installing the visible laser and associated optics
• Testing the rotation mount and translation mount
• Testing y-arm chassis

The Medm screen is now in a workable form if not particularly finessed.The screen is called TCS_CHETA.adl and a shortcut was added for the X and Y arms by camilla to the TSC screen.
There is still work to be done here calibrating the powerdetectors and power meters.
note: currently power in for the rotation mount .adl is the laser diode current and should be changed to laser power when calibrated

S. Muusse, C. Compton, G. Vajente

We are still in the process of testing the CHETA electronics integration and have began fixing the optical setup on the ITMY Table to test the sensor in situ.
The optical system was realigned with the lenses, waveplate and polariser repositioned to ensure lower 4.65um intensity on the pickoff to prevent burning after the issues in post. All core optics for the 4.65um beam have been placed and we are in the process of adding the sensor paths and laser dumps. 

Electronics:
We tested all the laser diode and TEC controller ports on the chassis which were working. It is worth noting when connected to the Laser Enable control the diode will not turn on unless this is enabled and can be used to shut off the laser power.
The thermal power meter input was also working and power changes can be seen on ndscope
I've put in a table the status of all the CDS I/O we've tested so far:

Some notes are that:
PD_C is the thermal powermeter 
PD_A and PD_B are the PDs

We aim to installl the PD setup tomorrow and test its electronics. 

Medm
Adjacently, there was continued progress on the medm, a flipper control was installed using SQZT7 code, the slow PD was added using LSC_CUST_DCPD.adl and QPD using QPD.adl. Both will be tested in the coming days on the actual system and the rest of the controls added.

02/23 S. Muusse, C. Compton, G. Vajente, S.Goswami, B. Wu 

The electronics chassis was brought into the lab today (thanks Phil and Dave) and we began testing the integration of the optomechanics with the CDS. An ethernet cable was run into the JOAT CHETA lab to connect to the server.  A variable power supply was brought into the lab to power the chassis at the required 24V along with a linear power supply required for the rotation stage and translation stages. 
The flipper I/O input and output had to be configured for Beckhoff communications using this guide.
The current status of our testing is as follows:
Working:

• Flipper
• PD
• Power meter

Not working:

• Rotation mount 

Untested:

• Translation stage

We have realised during this process that the flipper isn't powered by the SMA connectors and requires a seperate power source. This was not considered in the initial panel design and is not currently supplied by the chassis. There is a spare blank connector input/output slot which can be used. 

We have begun making the medm display for the CHETA system based on the current CO2 medm which shares many optomechanical systems. CHETA isn't currently on the TCS screen so to run the medm display currently the following command must be run to access the work in progress. 

medm -x -macro 'USERAPPS=/opt/rtcds/userapps/release/,SITE=LHO,site=lho,IFO=H1,ifo=h1,OPTIC=X,OPTICF=ITMX,name=AWCITMX,RT_MEDM=/opt/rtcds/lho/h1/medm' TCS_CHETA.adl 

To open the medm in a configurable format:
 medm TCS_CHETA.adl 
Alternatively to edit the code files:
code medm TCS_CHETA.adl 

Further alignment on the ITMY table was completed with almost all optics now mounted on the table. 

The slow controls software was updated to include the ChetaX  electronics. The chassis is currently in the MSR for test purposes, but will be moved to the cheta lab next week.

Channels are located under H1:AWC-ITMX.

Closes FAMIS#28228, last checked 88988

TCSX: 30.5 - Did not add water

TCSY: 10.4 - Did not add water

Flow and filters looked good, but had to remove a notification about preventative maintenance for the filter for both chillers (TCSX, TCSY) in order to see the flow rates. 

No leak in water cup

FAMIS 38837

CO2 lasers have been off for the past month for vent activities and HWS SLEDs were just turned on a few days ago, so this month's trends don't show much activity.

M. Todd, S. Muusse, C. Compton, S. Dwyer

I wanted to get another measurement of what the HWS think the coupling factor is for thermal lens from ring heater power.

The HWS were not on, so after filling out a work permit Camilla and I went out and turned on the HWS SLEDs. Then we restarted the HWS codes in the individual computers. We also asked Jim to take ITMY ISI to fully isolated.

After waiting about 25 minutes for the HWS to get a baseline reading we turned up both ITMY and ITMX ring heaters by 4W (2W/segment). The HWS will track the defocus and I will compare with my models tomorrow morning. I wanted to do both ITM ring heaters to get a self-consistent measurement.

We also plan on doing single bounce OMC scans tomorrow morning with the ITMs being sufficiently thermalized after the RH turn on. This should give us another lens (punny pun here) to look at the thermalization business.

Closes FAMIS27833, last checked in alog88799

Values added to spreadsheet. 

TCS Monthly Trends Famis 38836
There are some large spikes in this data on days where we have someDAQ restarts.
 

S. Muusse, M. Todd

Lens realigned on X-arm CHETA table for corrected focal lengths and the beam profiled which had better agreement with the model. ITM beam size from fit are much closer to ideal beamsize on ITM (≈ 52.7mm).

• Model was updated to use measured L1 focal length replacing manufactorer spec which was given for 588nm.
• Lens were repositioned based on the updated model
• Beam was profiled after L2 and used to fit q-parameters (attached). This was completed using a non-linear fit where M2 was fixed to 1
• Modelled beam parameters are just outside of the uncertainty bounds on the fit. We are suspicious of higher order mode contibutions effecting our fit especially in the vertical axis.
• Beam profiler is being shipped to LLO

Fit for profile after L2 vs model 

Beam radii at ITM is foudnfrom fit by propagating the fit q to the ITM.

S Muusse, M. Todd

New QCL unit (0920) has been put in place of original unit (0923) which is malfunctioning (cause unknown). Initial profiling has taken place and L1 focal length is 10% larger than spec.

QCL unit failure summary:

All day on 2026-01-21 we were running the laser at 900mA doing beam profiles and alignment work. No malfunctioning was witnessed and the laser unit was operating as expected, similar to the laser unit we had run in December for a week. Before lasing we set the following limits on the LD and TEC, per the datasheet.

1. LD current limit was set to 1.05A
2. LD voltage limit was set to 12.9V
3. TEC operating temperature was set to 20C

On 2026-01-22 we turned the laser on to do some more beam profiling with the same limit settings as yesterday, but setting the LD current to 1A (forward voltage was around 12.2V) as was done when we originally profiled this laser in September. We were in the middle of setting up for a new beam profiling measurement (alignment showed the beam was fine, as usual) and we blocked the beam with a high power beam dump at the laser head while installing the profiler. Upon removing the beam dump, we noticed no power was coming out of the laser, and then noticed the forward voltage had dropped to around 800mV. We noticed no sounds or smells or any other signs that something had stopped, only sudden lack of light coming from the unit. All other settings were fine, meaning the controller had not faulted and was still outputing 1A LD current and the TEC was maintaining 20C.

We ran the following checks to see if we could remedy the problem, without success.

1. Checked the cable connection to the laser unit (pins on the laser unit looked fine)
2. Checked the Laser Controller cable connections (pins in the DSUB connectors looked fine)
3. We tried a completely new laser controller box and new cable. The settings were similarly set and the same behavior was seen with the forward voltage response to the LD current setpoint.
4. We tried changing the TEC setpoint to be 25C, and the same behavior was seen with the forward voltage response to the LD current setpoint, and failing to lase as usual.
5. We used the same cable and laser controller on the previous QCL unit, and it operated as expected --- lasing fine as usua

QCL 0920 profiling summary:

Replaced broken unit with 0920 and confirms it lases as spec'd. We built telescope as modelled but beam profile was 75% of expected beam width at L2. We subsequently profiled the laser output and confirmed QCL output q measured previously by Matt was still correct. We became suspicious of the true focal length of L1. Then we profiled multiple places after L1 and fit a q parameter using a non-linear fit. A plot of this fit is attached. Using these 2 q parameters the focal length of L1 was estimated to be 220mm instead of 200mm as spec. We think this is mostly because L1 focal length stated by manufactorer is for 588nm where the refractive index is almost 3% larger than at 4.6um. Focal length in the model was modified to reflect our estimated f1 which predicted a beam size closer that measured earlier. 
Side note: the scanning slit beam profiler reflects significant amount of 4.6um light which is observable on a thermal beam card. 

FAMIS 27831, last checked in alog88548

No water was added, filters looked good, and Dixie cup was dry. Updated T2200289 spreadsheet.

M. Todd, G. Vajente, L. Dartez

Thursday 12/18

1. We compared the beam profile that we fit to the modeled beam in that region, as well as what both of these beams look like at the ITM. We were initially very confused so we went back and more carefully placed the optics, taking care of the of and between the lenses in the telescope.
2. It seemed that the astigmatism was much worse than anticipated so we thought about tilting one of the lenses and seeing if we could compensate for the astigmatism. This gave us pretty confusing results, and especially because the fit to the first dataset was yielding non-physical values. For reference, the fit is done by fitting a quadratic to the beam radius squared as a function of z (i.e. w² = a+bz+cz²).
3. After deliberating in the control room, and returning to corroborate the fintrace model with jammt, we came to the conclusion that the telescope model is sensible; however, the measurement that we were taking is not descriptive enough of the beam to understand how the active telescope performs.
4. We finally decided to go in and take out the pick off to get as close of beam profile measurements to the waist of the beam after L2. We then shifted L2 5cm back toward the laser which was closer to the nominal position in the modeled layout. Here are the two plots of those beam profiles with their fits (I used a quadratic allowing M2 to vary, Gabriele has plots of minimized error of a Gaussian beam). L2 5cm further from M1 than the model. L2 close to model nominal position.

M. Todd, G. Vajente, L. Dartez

Wednesday 12/17

1. Additional optics mounted
   1. ZnSe 2” lens
   2. 2” silver and gold flipper mirrors (not installed)
   3. Additional beam dump for reflection of Polarizer2
2. We had the PD chassis milled out further to take an offset out that prevented the board from sitting flush.
3. We noticed that the coating had been burned on the first beam sampler we got from EdmundOptics. Emailed vendor to ask if this is common, because the power density is not at all expected to have produced this.
4. We also took beam profiles with a rail installed to get a fit of the beam evolution between M2 and M3. I made a fit of the data, assuming that M2 was perfect (I was having trouble with the nonlinear fit without M2=1, will revisit).

To do tomorrow:

1. Try and compare the lens solution to the fitted q we have from measurements.
2. Try and set up the coaligned visible laser

M. Todd, G. Vajente, L. Dartez

Tuesday 12/16

1. This morning we got the power monitor working with the old ICS computer that seemed to have the software on it already. We were not able to get the QPD software working because it requires Windows10 or newer; of course, this is only temporary because the other signals will be routed into the bekhoff eventually.
2. We got the package that arrived today with the beam profiler, and pins for the PDs. We took out the socket from one of the PD boards, but decided to have the chassis machined which should allow the sockets to fit in the chassis correctly.
3. We began, and made significant progress, on the alignment process for the optics. We got the beam mostly aligned well through all the optics, including lenses, to the output of the optics table. A few caveats
   1. We added a dogleg to the initial laser path so that the cables going to the feedthrough panel would not interfere with the laser .
   2. The first leg of the beam path along the long edge nearest to the rotation stage does not have enough room and will need to be readjusted.
   3. We will want to put the profiler in near the exit to see if the telescope is functioning as designed.
   4. The ZnSe lens needs to be mounted as well as the flipper. We still need to test the flipper.

FAMIS 27830 TCS Chiller top off

12/16/2025    Tony    30.7    100    30.8    10.2    125    10.4    Top of ball reading

M. Todd, G. Vajente, L. Dartez

Monday 12/15

1. We went through a checklist of things that still needed to be mounted, and decided to change the layout of laser position a bit to include a dogleg so that the laser connector had more room, free from the cable connectors near the feedthrough panel
2. Redesigned the feedthrough panels, now the same design can be used for all 4 tables (2 at each site) – and got a quote to be ordered
3. Connected and tested the laser interlock 
4. Mounted and installed laser (SN 0918) & cooler, confirmed that it draws current & delivers a reasonable amount of power as read out on the powermeter
5. Assembled pedestals for the lenses & various optics using assorted spacers to ensure center of all optics is at 4” height
6. Started a cart for additional components that we’ll need since we’re dipping into table 2 parts due to the adjustments we’re making to the layout

To Do:

1. Finish mounting the mirrors in the flipper mount (supposed to be a double mirror)
2. Mount the ZnSe QPD 2” lens.
3. Implement the dogleg
4. Align the optics
5. Profile the laser where the translation stage is now or where the beam is supposed to be going.
6. Integrate the power meter into a laptop with a usb?

On Sept 4th we had a longer commissioning period to allow us to heat up OM2.  The main goal was to use this to characterize the mode matching of the arm cavities to the OMC, but we also made some other interesting measurements.

Summary:  heating up OM2 now costs us about 1% of optical gain, while it used to cost us 2%.  Heating up OM2 also changed the SRCL offset needed to get flat squeezing significantly, and reduced the amount of squeezing that we could get (without adjusting psams).

The interferometer unlocked (86727) while Jennie Wright was running the DARM offset step script with OM2 cold, to get a measurement of HAM6 throughput and look at OMC refl before heating up OM2.  As that link says, there wasn't an obvious connection between the DARM offset script which was in it's final steps (nearly back to normal) when the lockloss happened. 

We turned on the OM2 heater while relocking after some back and forth, then had an commissioning caused lockloss while trying to recover.  By the time we were relocked, OM2 was heated up according to thermistor 2, which is the thermistor who's timescale matched the timescale of optical gain changes in the past (see screenshot of June 2023 example).  We also had a large earthquake while relocking, so we paused after power up and before going to nominal low noise, so we do not have tracking of the optical gain using pcal in the first 30 minutes of this thermalization. 

The optical gain in this thermalization seemed to be fairly similar to the previous lock where OM2 was cold in the first hour.  The change in optical gain between OM2 hot and cold was much smaller this time around, so we needed to see the full thermalization in order to see what the gain change was.  We set the OM2 heater off 4 hours and 5 minutes after the power up, the attached screenshot shows a trend of optical gain during the previous thermalization while OM2 was cold, with a vertical cursor 4 hours 5 minutes into the lock.  The horizontal cursors show where the optical gain was at 4 hours and once the thermalization was complete, the optical gain continued to increase by 0.2% after the first 4 hours. The next screenshot shows vertical cursors also at the time of power up and 4 hours later, and the horizontal cursors are the same as on the previous screenshot (OM2 cold).   It seems that the optical gain was about 1.1% lower with OM2 hot than cold, although fitting these two thermalizations to an exponential might bring them closer by as much as 0.2%. Our current ring heater settings are 0W on ITMY, 1.5 W/segment on ETMY and 0.44W/segment on ITMX and 1W/segment on ETMX.

Since this is a different result than in the past times of OM2 changes, I've gone back to look at old times when we did this change.  One possible explanation for the difference could be ring heater settings being different. 

• 12/18/2023, cooled off while unlocked, optical gain increased 1.8% ETMX +ETMY RH 1W, ITMX 0.44W
• 9/19/2023, heated while unlocked, optical gain dropped 1.9%   (this time is confusing, it seems like the thermistors which had been disconnected were plugged in and looked to be thermalizing, but the set power was unchanged).
• 7/19/2023, heated in steps, 71484 ifo unlocked and relocked several times, perhaps calibration was reset making optical gain comparison confusing. (it did seem to drop by about 2%, but this seems more like a calibration reset) ETMX + ETMY RH 1W/segment, ITMX RH 0.44W/segment
• 7/12/2023 OM2 cooled off in lock, lockloss happened in the early part of the cooling (2% optical gain increase), ETMX + ETMY RH 1W/segment, ITMX RH 0.44W/segment
• 6/27/2023 OM2 heated while in lock, optical gain dropped by 2%, ETMX + ETMY RH 1W, ITMX RH 0.44W/segment, 0 on ITMY.

Once the OM2 heater was turned back on, the optical gain increased by nearly 1%, but the IFO lost lock before that thermalization finished.  There was a 2% decrease in POP18 during the cool off and a 3 urad shift in SRM top mass. 

While OM2 was hot, we did a few tests.

• We had a large change in the SRCL offset needed to reduce the squeezing rotation: 86739  This is interesting, in the past we have tried to change SRM alignment to see an impact on this number and it was a much smaller change.
• No squeezing time for a senstitivty comparison (not much change): 86788
• quick squeezer data set (before SRCL offset updated: 86736 with SRCL offset updated: 86739 ) , to see a comparison with OM2 cold see Camilla's plot from this morning
• Jennie Wright did DARM offset steps with OM2 hot, and cold.

Ansel, Sheila, Camilla

Last week, Ansel noticed that there is a 2Hz comb in DARM since the break, similar to that that we've seen from the HWS camera sync frequency and power supplies and fixed in 75876.  The cabling has not been changed since, the camera sync frequency has been changed.

Our current camera sync frequencies are: ITMX = 2Hz, ITMY = 10Hz. We have typically seen these combs in H1:PEM-CS_MAG_LVEA_OUTPUTOPTICS_Y_DQ. With a 0.0005Hz BW on DTT I can't easily see these combs, see attached.