QOSEM Signal Chain Testing

[Tom Roocke, Oli]

Summary: The 6 QOSEMs and their signal chain for the BBSS are operational with the final sat amp, CER wiring, CDS mapping, in vac DB25 extension cables. All that remains to test before SUS installation is the duopus cables, which are in C&B currently.

In continuation from yesterday, we are testing out the QOSEM signal chain prior to installation of the BBSS. Yesterday we verified the sat amp was still functional and the readouts were showing up in CDS appropriately. See LHO:90072. Today we checked both the DB25 to DB25 extension cables, and the QOSEMs. To come is testing of the duopus cables, which are still in C&B.

DB25 Extension Testing:
Using a known functional Duopus cable (S2600215), and inair DB25, we tested the three DB25 extension cables by reading for the QOSEM coil resistance and diode drops at the in air DB25, where it connects to the sat amp. See the signal continuity test section in T2600170 for more information on this. All 3 cables are functional.

S2001548: DB25 working
S2100358: DB25 working
S2100410: DB25 working

QOSEM CDS Readout Testing:

Using a known functional Duopus Cable (S2600215), DB25 Extension (S2100410) and in air DB25, we checked for the open sum voltage in the CDS readout. This is the voltage seen on the sum channel of the QPD with no lens installed. Seeing a nonzero voltage here indicates that the QOSEM LED, QPD and signal chain are functional, but will be far lower than the operational sum level when the lens flag is appropriately focusing light onto the QPD. We tested the open sum voltage for all 6 QOSEMs designated for the BBSS. All QOSEMs and there signal chain are functional.

S2600008: working with open sum of 13910
S2600009: working with open sum of 14755
S2600010: working with open sum of 15550
S2600011: working with open sum of 15470
S2600012: working with open sum of 15348
S2600013: working with Open Sum of 14380

Measurement of jitter with IMC WFS at 10W

Summary: Since I had trouble seeing a noticeable improvement in jitter by looking at the IMC WFS in this alog #89988 where the PSL output power was 2W, I looked at times when we were at 10W PSL output power to see if we were limited by shot noise. The measurements at 10W show that we might have decreased jitter but I checked the QPD sum values for the measurements after JAC was installed vs. before and we are near the edge of the QPDs.

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I took reference times, when our input power was 10W to see if this gave a better measurement of jitter

Time 1: 2025/11/17 16:13:17 UTC during initial alignment. Without JAC.

Time 2:2026/03/19 15:31:23 UTC during commissioning when HAM1 was at vacuum.

Image one shows the yaw measurement, there is again a difference in the value at DC of the QPD ASDs. It looks like the peaks seen between 40 and 1000 Hz are slightly better with JAC than without JAC but it is only obvious on WFS A and B QPDs (top left plot comparing green and purple lines for WFS A and red and yellow lines for WFS B).

Image two shows the pitch measurement, there is again a difference in the value at DC of the QPD ASDs. It looks like the peaks between 40 and 1000 Hz are slightly better with JAC than without JAC but it is only obvious on WFS A QPD (top left plot comparing green and purple lines).

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I also checked that the QPD sum values changed between my reference times during O4 and after JAC installation. See these four images.

1. 2W reference time during run. A and B QPD SUMs were arpund 0.03 counts.

2. 2W reference time after JAC installation. A and B QPD SUMs were arpund 0.002 counts. Maybe we are now nearer the edge of the diode?

3. 10W reference time during run. A and B QPD SUMs were around 0.16 and 0.13 respectively.

4. 10W reference time after JAC installation. A and B QPD SUMs were around 0.009 and 0.008 respectively. Maybe we are now nearer the edge of the diode?

Running IOC to convert CP1 Regen temp gauge signal to PT100A EPICS channel

Gerardo, Jordan, Richard, Patrick, Fil, Jonathan, Dave

A temporary vacuum gauge was connected to the h1vacly beckhoff terminal to monitor the CP1 regen over the coming weeks. In lui of adding this to the production h1vacly code, we chose instead to read the raw voltage from Beckhoff and serve this data on a temporary IOC.

I wrote pt100a_ioc.py which reads the raw voltage from the Beckhoff channel H0:VAC-LY_TERM_M14_CHAN2_IN_VOLTS. It reposts this value and then converts it to torr. These channels exported are:

H1:VAC-LY_Y5_PT100A_VOLTS

H1:VAC-LY_Y5_PT100A_PRESS_TORR

Jonathan setup a containerized IOC on the VMs to run this IOC.

We created H1EPICS_VACLY.ini to add these channels to the EDC. The DAQ+EDC was restarted at 16:21.

This work is in support of the CP1 regen work permit.

 

 

 

BSFM Transfer Functions good on test stand

To check for any rubbing or other issues that the BSFM might be encountering on the test stand, I took some transfer functions today after Betsy plugged the top mass in yesterday (90063). The measurements have really poor coherence because the BSFM isn't covered, but it's decent enough to at least verify that TFs are looking good and we aren't near touching anywhere.

Data
$(sustrunk)/BSFM/H1/BS/SAGM1/Data/2026-04-30_1615_H1SUSBS_M1_WhiteNoise_{L,T,V,R,P,Y}_0p02to50Hz.xml

Ops Day Shift Summary

TITLE: 04/30 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: Transfer functions were run on the BS, water lines on the TCSX table were replaced, a galled HEPI spring at BSC2 was removed, and a feedthru on HAM3 was swapped out.
LOG:

Start Time	System	Name	Location	Lazer_Haz	Task	Time End
15:47	EE	Fil	LVEA	-	Running VAC cable	18:54
16:01	FAC	Kim	LVEA	-	Technical cleaning	17:11
16:17	TCS	TJ, Camilla, Madi	LVEA	-	CO2X water line work	18:18
17:11	IAS	Ryan C	LVEA	-	Grabbing a laptop	17:28
17:12	SUS	Oli	CR	-	BS transfer functions	18:59
17:16	ISC	Elenna	Opt Lab	YES	BHSS OMC work	18:18
17:40	FAC	Kim	LVEA	-	Technical cleaning	18:21
17:44	SEI	Jim, Randy	LVEA	-	BSC2 HEPI spring replacement	18:49
17:48	VAC	Gerardo	LVEA	-	Check in w/ Fil	18:49
17:55	VAC	Travis	LVEA	-	HAM3 feedthru work	19:15
18:02	VAC	Betsy	LVEA	-	HAM3 feedthru work	19:15
18:50	VAC	Jordan	X-arm BTE	-	Taking pictures	18:54
19:01	PEM	Ryan C	LVEA	-	BSC2 DM tests	19:41
19:26	CDS	Marc, Patrick	MER	-	Checking a chassis	19:36
19:31	SEI	Jim, Randy	LVEA	-	BSC2 HEPI spring replacement	20:25
20:11	CAL	Tony	Opt/PCal Labs	Local	Beam profiling	Ongoing
20:31	FAC	Randy	LVEA	-	Craning table over X-arm	21:23
20:33	TCS	TJ, Madi	LVEA	-	TCSX table water lines	22:01
20:39	AOS	Betsy, Anna	LVEA	-	Walkabout	21:45
20:39	SUS	Tom, Oli	LVEA	-	QOSEM testing	21:54
20:57	SUS	Fil	LVEA	-	QOSEM testing	21:52
21:12	SAF	Richard	LVEA	-	Checks	21:30
21:13	CAL	Dripta	PCal Lab	Local	Beam profiling	Ongoing
21:32	IAS	Ryan C	LVEA	-	Power cycling FARO	21:48
21:38	TCS	Camilla	LVEA	-	TCSX table water lines	21:57
21:58	SUS	Oli	CR	-	BS transfer functions	23:03
22:24	VAC	Jordan, Gerardo	LVEA	-	CP1 work	23:13
22:39	SUS	Tom	LVEA	-	QOSEM electronics	Ongoing

TCSX table water lines all swapped and tested, but left off over the weekend

Camilla C, Madi S., TJ S

We finsihed swapping out all of the flex lines on the TCSX table, and have tested the lines at full flow. We will leave the chiller off over the weekend.

We left off last week (alog89976) with the 1/2"OD lines that were spec'd on the BOM not fitting in the Kentek beam dump. I looked it up and the push fittings on the beam dump actually take 10mm OD lines. Ordered those, and we finally were able to install them today. We first plugged in the table lines to the rest of the systme lines but with the chiller off, to get a bit of water on the table, and immediately noticed a leak at one of the beam dump fittings. We tried cutting and reseating the line, but it still had a drip. We replaced the dump with a spare and that seemed to do the trick.

In an effort to put water back in all of the table lines in a lower pressure manner, we hooked one end of the table lines to a wet vac and dipped one in a bucket of lab water. This pulled enough water through the lines and then we capped both lines and let it sit over lunch. There were no drips or evidence of drips when we returned, so we connected the table lines back into the system lines. Madi and I were on the phone while I turned the chiller on with the back 3way valve turned to recirculate (down). I then very slowly moved it up and Madi observed water starting to flow through the system. We kept slowly increasing the flow and watching for leaks until we were at our full 4.0gpm as read from the chiller. 

We decided to keep the chiller off over the weekend, but will turn it back on Monday and will keep a close eye on it since I'm a bit paranoid.

WP 12469 updated the experimental framewriter

I updated and restarted the frame writer on h1daqfw2 yesterday at 1:37pm and today at 3:04pm localtime.

HAM3 D6 flange feedthru swapped

The D6 feedthru on HAM3 was swapped from the 3-port version with 3x Dual DB25 feedthrus to the single piece 12x DB25 connector feedthru.  We re-attached both the in-vac and in-air cables that were originally in that port so that the SUSes can be controlled.

SPI Fundamentals: DEMOD Filter Digital Signal Processing Trade Study

J. Kissel, S. Koehlenbeck

Executive Summary: as an initial guess -- we chose DEMOD parameters as follows:
    . SIG Bank = NO pre-demodulation filtering (just frequency-independent calibration)
    . I & Q Banks = a comb of notch filters at 4096 Hz (the 1f DEMOD frequency), and 8192 Hz (the 2f DEMOD frequency) and a super simple single-pole 200 Hz low-pass.
as the DEMOD filters for the demodulation of signals from the SPI pathfinder's IFO PDs.

I now have a user interface (LHO:90006) to the SPI pathfinder front-end model infrastructure (LHO:89777), so we're now thinking about filling in that infrastructure with real science (or at least real digital signal processing). 

SIG filters
One of the core principles of the SPI pathfinder's longitudinal degree of freedom is demodulating the 4096 Hz between note between the MEAS and REF beam. We only expect to use the SPI up to ~10-50 Hz, as the demodulated interferometer PDs noise floor begin to be limited by ADC noise ~5 Hz -- see LHO:83412 and detailed noise budget in Figure 1bii.1 in T2400145. Of course, it remains to be seen how much displacement signal we see above this noise floor.

Traditionally when demodulating nowadays, we're looking for the amplitude and phase of the excitation line we inject among surrounding noise that we don't want (think ADS lines, calibration lines, violin mode and PI damping, etc). In that case it makes sense to band-pass the raw signal pre-demodulation -- this is why you see narrow band-passes in many SIG banks. However, in the case of the SPI IFOs and other heterodyne IFOs, we're actually quite interested in the "noise" -- the "excitation line" is instead the carrier frequency, and the "noise" is the phase signal that we then interpret as differential displacement. As such, the design of the SIG, I and Q filters has an entirely different mentality:
    - in the "find the amplitude and phase" mentality, you want a tight band pass on the excitation frequency in the SIG bank, and then as low-a-frequency low-pass filter that you're patience allows.
    - in the "measure the sideband noise out to 100 Hz or so" mentality, you want as little filtering magnitude / phase distortion as possible from any filtering while sill removing any noise above the band of interest from the signal, post demodulation -- which is typically down-conversion from the 2f signal.

So -- we want *no* filtering in the SIG bank prior to demodulation, and a low-pass that has minimal in-band magnitude ripple and minimal in-band phase loss.

Attached is a trade study of filters that show the magnitude, phase, and step response for several options. All these options are installed in the MEAS A and B and REF A and B I and Q filters, but we've turned only the comb and single pole.

HEPI spring galled 2012~ish replaced on BSC2

Since we removed the cartridge from BSC2, I took the opportunity to try to remove a spring that had galled when we first installed the BS & ISI stack for Advanced LIGO. I initially tried coaxing the preload nut on the end of the spring free with alcohol and a couple of long wrenches, but eventually that wasn't enough. With Randy's help, we pulled the two cap pieces off the end of the HEPI house spring tube and lifted the cap, load cell and spring out. This spring was taken to the high bay where Randy used a porta-band to cut the galled nut off, allowing us to retrieve the other hardware off the spring. Was suprised to hear Randy say the kind of dull looking blade on the portaband had no difficulty with steel cap on the spring.

A spare spring from LLO has been installed in it's place, torqued to the crossbeam foot, the old load cell and hardware have been added above.

I didn't get any photos of the work really, but here's a shot of the de-galling method we used. 

QOSEM Sat Amp CDS Checks

[Tom Roocke, Oli]

Summary: QOSEM Sat Amp installed, run into ADCs and Coil drivers, injected signals into sat amp appearing where the should in CDS.

Yesterday the QOSEM Sat Amp was installed into the SUS-R2 rack (D2300383, LHO:90004), along with the in air DB37 wiring into the ADC. We checked that the signal routing into CDS was good, by injecting a current into the QPD inputs on the front panel. We used the portable calibrator found in the EE shop, to generate a 3.5mA DC current, which is about the expected level of photocurrent during nominal operation of the QOSEM. The negative output of the calibrator is connected to the cathode input for the QPD (pins 16 and 21 on the DB25 QOSEM inputs on the sat amp, see D2500300), and the positive output is connected to the anode inputs (pins 25, 12, 24, 11 and 20, 7, 19, 6). 

We injected current into the anodes for all 6 channels in the sat amp, and all showed up in CDS on the expected channels. Next to check is the QOSEM Duopus cables, which we are waiting on from C&B. After which that should be the full signal chain tested.

Thu CP1 Fill

Thu Apr 30 10:06:27 2026 INFO: Fill completed in 6min 24secs

 

Ops Day Shift Start

TITLE: 04/30 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: 4mph Gusts, 2mph 3min avg
    Primary useism: 0.07 μm/s
    Secondary useism: 0.14 μm/s 
QUICK SUMMARY: Several projects continue today, including surveying of the BS on the test stand and setting up new electronics for the BBSS.

Yesterday, Betsy had turned the HAM3 QPD chassis back on after having it off for replacement of the chamber feedthru, and comparing at least the NSUMs of ASC POP A and B to before the chassis was turned off, the levels are a little lower and a bit noisier (see attached).

STS-2 Signal Distribution

WP 13216
ECR E1400386

Cables for the STS-2 signal distribution removed. Part of ECR E1400386. The STS-2 interface chassis were left powered off. Part of WP 13149.

Mechanical Test Stand / BSC2 & HAM3 Rack Work

a-Plus O5 SUS BSC2 HAM3 HAM4 (susb2h34) System Wiring Diagrams - D2300383

Electronics and cabling for BSC2 and HAM3 suspensions (BBSS,  LO1, LO2) completed per D2300383. The new HAM-A and Triple Acquisition Drivers were left powered off (BS Bot, LO1, LO2).

Four Kepco supplies were installed in the CER Mezzanine. Supplies provide power to the SUS-R2 rack. A second junction box was added to SUS-R2. They have been set to ±18V and ±24V, shared between SUS and SPI

Final dressing of the field cables going from the biergarten to the West Bay Mechanical Test Stand completed. They will be used for testing of the old and new BS. Some cable swapping in the CER is required for testing the QOSEMs (some old BS electronics will be reused).

BS on Test Stand - Top Stage is damping again

I connected the temp cables which Fil routed for us to the BS Satellite Boxes in the rack in the biergarten.  I disconnected the "to chamber" cables on the Sat amps and connected our temps to those.  After some resorting of the BS Top Stage BOSEM cabling at the ISI, I was able to get the appropriate signals from the appropriate 6 BOSEMs on the medm.  
I am not sure that we will reuse these cables but for the record (since I couldn't find an old BS alog with this info), the Cable Bracket on the ISI is stuffed with these D1000225 cables:

S1106798 Against ISI (Top floor) - BS F1, F2, F3, LF
S1106797 Middle floor - RT, SD
S1104787 Lowest floor - M2 - medm no longer connected tho, says Oli - not plugged in right now anyways

We have more trending to do tomorrow but the F1, 2, 3 Face BOSEMs seem to be "in deeper" while the LF, RT, SD DOFs all show about nominal OSEM position from when it was in the chamber a few days ago.  Chewing on what this means wrt the structure position and ISI/Test Stand level, etc.

Note, I also had to partially uncover the front of the ISI to get the cables out and pinned in such a way to connect to the mock feedthru and then dirty cables.

HAM3 chamber vent work - SLiC, BAFFLE ASSY attached to both PR2 and MC2

Mitchell, Rahul

This morning we entered HAM3 chamber and attached the baffles (for stray light control) to both PR2 (HSTS) and MC2 (HSTS) suspensions. The baffle assembly design is shown D1700257_V5. These baffles were attached (directly mounted on the HSTS structure) on both the sides of the optic, i.e  HR and AR side.

Before attaching the baffles I inspected both the optics and they looked nice and clean, hence didn't needed any First Contact cleaning. 

I am attaching pictures below for reference.

We found that both PR2 and MC2 had two missing 1/4-20 threads on the HR side for attaching the mounting rail (D1700249_v1) of the baffle (Mitchell will attach a picture showing the same). Typically, these rail need four holes on the structure for securing them. However, we used the lower two threaded holes for attaching these mounting rail and they were rigidly secured. On the DCC I found that both PR2 and MC2 have D020023_V3 of the HSTS_Structural Weldment Assembly, latest D020023_V7 has more holes on the frame.

We also noted that one of the Siskiyou mount is very close to the MC2 baffle (AR side) as shown in the picture here. However, I can confirm that they are not touching and there is a decent amount of clearance between them. 

I still need to perform health checks on both the suspensions to rule out any rubbing and will post the results as a comment over here.

Note - counts on dust monitor were in single digit before and after entering/exiting the chamber (Thanks to Ryan C for arranging this).