J. Kissel, T. Roocke

I was crossing the t's and dotting the i's on our documentation to better understand what calibration / compensation to install into the new SPI front-end / MEDM infrastructure. 

As such I was reconciling / validating the calibration info that Sina put in LHO:89739 (originally informed by derivations in E2600104) against the info Tom put in the three travelers 
    - S2500711 (Variant 1 for the HAM2 YAG444s), 
    - S2500712 (Variant 2 for the HAM3 4x FFD200s and one YAG444), and
    - S2500713 (Variant 3 for the HAM3 additional 2x FFD200s)

Two things were amiss:
(1) The values of resistors and capacitors were not consistent between Sina's "R4 Resistor value now (kohm)" and "C5 capacitor value now (pF)" columns, and what Tom stated in the traveler update. As such, I asked Tom to give me more detailed confirmation -- and he delivered excellently:
    S2500711 (Variant 1 for the HAM2 YAG444s)
    CH1-4 
        . R4 = 1.54kohm (P1.54KFCT-ND) 
        . C4 = 2.2nF (399-8171-1-ND)

    S2500712 (Variant 2 for the HAM3 4x FFD200s and one YAG444)
    CH1-2 
        . R4 = 4.99kohm (P4.99KFCT-ND) 
        . C4 = 560pF (PCC561BCT-ND)
    CH3-8 
        . R4 = 3.32kohm (P3.32KFCT-ND)
        . C4 = 1nF (PCC102BCT-ND)

    S2500713 (Variant 3 for the HAM3 additional 2x FFD200s)
    CH1-2 
        . R4 = 53.6kohm (P53.6KFCT-ND) 
        . C4 = 220pF (478-1484-1-ND)

(2) In our testing of the TIAs both *before* and *after* these component values were installed, we were comparing values measured power values with a Thorlabs S121C power meter (in [mW]) against the TIA ADC output voltage on the positive leg *only* (in [V]), after having verified that the negative leg consistently reported the negative of the positive leg on all channels. 

In E2600104-v1 the AA column for "PD Calibration" -- and thus Sina's "PD calibration (mW/V)" column in LHO:89739 is the ratio of the power and positive leg only, and thus missing a factor of 2.0.

So ... there's the updated table, with 
    - the transimpedance gain, "TIA gain" calculated as R4 * 2 [V_SE/V_DIFF], with the factor of two from the last ADC driver stage 
    - when engaged (rather than bypassed), the whitening stage with 
           z1 = 1 / ( 2*pi* (R1*C1 + R3*C2 + R3*C1) )
           z2 = (R1*C1 + R3*C2 + R3*C1) / ( 2*pi* (R1*C1*R3*C2) )
           p1 = 1 / ( 2*pi* (R1*C1) )
           p2 = 1 / ( 2*pi* (R3*C2))
    - FBR_PWRIN single-element PD Calibration at DC
            (power at PD) / ( 2 * (ADC volts pos leg) )
    - IFO single-element PD calibration at DC
            (SIG power + LO power) / ( 2 * (SIG ADC volts pos leg + LO ADC volts pos leg) )
    - QPD segment calibration
            percentage of voltage = ADC volts pos leg of each segment / (total pos leg voltage on all segments)
            (total power at QPD * percentage of voltage) / ( 2 * (ADC volts pos leg of each segment) ) 
    - a 16 bit ADC with 40 Vpp DIFFERENTIAL range, i.e. 40 / 2^16 = 6.1035e-4 [V/ct] or 2^16 / 40 = 1638.4 [ct/V] (see T1100538)
           


    DIGITAL NAME     ANALOG    R4        C4       TIA Gain   PD/SEG Calibration   TIA HF Pole    Whitening 
                     NAME      [kOhm]    [nF]     [V/A]      [mW/V]               [kHz]          (z1,z2:p1,p2) [Hz] 
QPDA
    OL_QPD_A_SEG1    CH1       1.54      2.20     3.08e3     2.0556               46.976         (0.394, 8.06e6: 39.8, 79.6e3)    
    OL_QPD_A_SEG2    CH2       1.54      2.20     3.08e3     2.0556               46.976         (0.394, 8.06e6: 39.8, 79.6e3)    
    OL_QPD_A_SEG3    CH3       1.54      2.20     3.08e3     2.0556               46.976         (0.394, 8.06e6: 39.8, 79.6e3)    
    OL_QPD_A_SEG4    CH4       1.54      2.20     3.08e3     2.0556               46.976         (0.394, 8.06e6: 39.8, 79.6e3)    


IFO
    IFO_MEAS_A       CH1       4.99      0.56     9.98e3     1.0959               56.955         bypassed
    IFO_MEAS_B       CH2       4.99      0.56     9.98e3     1.0619               56.955         bypassed
    IFO_REF_A        CH3       3.32      1.00     6.64e3     0.6042               47.938         bypassed
    IFO_REF_B        CH4       3.32      1.00     6.64e3     0.6304               47.938         bypassed   

QPDB
    OL_QPD_B_SEG1    CH5       3.32      1.00     6.64e3     0.3667               47.938         (0.394, 8.06e6: 39.8, 79.6e3)  
    OL_QPD_B_SEG2    CH6       3.32      1.00     6.64e3     0.3667               47.938         (0.394, 8.06e6: 39.8, 79.6e3)
    OL_QPD_B_SEG3    CH7       3.32      1.00     6.64e3     0.3667               47.938         (0.394, 8.06e6: 39.8, 79.6e3)
    OL_QPD_B_SEG4    CH8       3.32      1.00     6.64e3     0.3667               47.938         (0.394, 8.06e6: 39.8, 79.6e3)

POWER
    FBR_PWRIN_MEAS   CH1      53.60      0.22   107.2e3      0.1154               13.497         bypassed 
    FBR_PWRIN_REF    CH2      53.60      0.22   107.2e3      0.1176               13.497         bypassed 


I've updated E2600104 (the google sheet), exported it and uploaded that to -v2 to corroborate.

FAMIS 31136

No major events of note this week.

As per WP 13205, remote ssh into the LHO DMT has transitioned from the old token authentication system to LIGO.ORG Duo.

As per WP 13118 CDS remote logins now require LIGO.ORG Duo.  CDS has been disconnected from the older token authentication system.

Remote ssh users who have not transitioned to LIGO.ORG Duo will need to do so.  See https://cdswiki.ligo-wa.caltech.edu/wiki/LigoOrgDuoSetup

If you have issues with logging in please let one of the CDS admins know.

TITLE: 05/04 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: 0.02 μm/s
    Secondary useism: 0.18 μm/s 
QUICK SUMMARY:

• Picket fence frozen 2 days ago
• BS test stand surveying continues
• HAM2 doors off tomorrow

On Friday I setup the QOSEM calibration rig in the triple lab, in the staging building. It consists of a motorored translation stage (open loop picomotor), which drives the QOSEM flag into and out of the QOSEM body, while the sum and difference voltages produced by the sat amp are monitored. The position of the stage, and hence flag is readout by a Mach-Zender interferometer (SmarAct PicoScale). This is all controlled by a laptop running a python script.

The purpose of setting up this rig again is to better calibrate each QOSEM going on to the BBSS M1, by taking calibration data with the exact sat amp and flag that each QOSEM will use.

Gerardo, Dave:

I have added the CP1 REGEN pump card gauge PT100A to alarms with Gerardo's requested alarm levels

<Channel name="H1:VAC-LY_Y5_PT100A_PRESS_TORR" low="1.0e-04" high="5.0e-01" fields="0" description="CP1 REGEN PUMP CART">

During the CP1 Regen the daily fills have been disabled. Verified it did not run at 10:00 today.

Alarms has been configured to expect GV6 to be hard-closed. The bypass for this alarm has been removed.

I've created an MEDM for the new PT100A EPICS IOC which reads the raw ADC Voltage from h0vacly (TERM14-CHAN2) and converts it to PRESS_TORR. It can be opened via the VE pull down on the SITEMAP (see attached).

The python code pt100a_ioc.py had a connection issue yesterday when we lost network connection to h0vacly during the closure of GV6. This resulted in a freeze of its value until I restarted the service Friday night at 20:50PDT.

Jonathan and myself installed a new version of the code this morning (Sat 02may2026 09:10 PDT) which should handle disconnection events gracefully.

I have added PT100A trending to ndshooter for 1 and 7 day lookbacks, e.g.  vac_pt100a_1_day.png (see attached, yesterday's value freeze clearly seen).

(Jordan V., Travis S., Dave B., Gerardo M.)

The CP1 soft regeneration officially started today at 4:56 pm local time, when we closed the bottom liquid draw valve.  We had a small issue with GV6 not wanting to hard close, we did two tries at hard closing this valve, it did close on the second try with a pressure of 65 psi.  The SS500 has been set to allow to pump despite the increase on pressure due to the lack of LN2 internal to CP1.  We used hoses to get the scroll pump exhaust out of the LVEA.  We will monitor the soft regeneration progress remotely.

TITLE: 05/01 Day Shift: 1430-2330 UTC (0730-1630 PST), all times posted in UTC
STATE of H1: Planned Engineering
INCOMING OPERATOR: None
SHIFT SUMMARY: GV6 was closed as part of the CP1 regen effort today, along with some beam profiling in the PCal lab and small tests on the QOSEM electronics.
LOG:

Fri May 01 10:08:36 2026 INFO: Fill completed in 8min 33secs

Gerardo, Jordan, Dave;

In the event of a REGEN pump cart failure we expect PT100A to show a large and rapid change in pressure. I have added PT100A to VACSTAT and set the trigger limits quite high to start with to prevent false positives. Note that currently the PT100A VACSTAT channels are not in the DAQ.

TITLE: 05/01 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: 0.01 μm/s
    Secondary useism: 0.11 μm/s 
QUICK SUMMARY: Work continues to prep for the BBSS; likely a quieter day today.

PT100A has been added to the VAC Overview MEDM. Overnight pressure trend also shown.

Camille (CIT), Austin , Rahul

This morning we went to HAM7 chamber and changed the preload on ZM4 (P-SAMS) suspension as per the document E2300463_V1. This changed the RoC of ZM4 mirror without the PZT actuation. Given below are the details of our work - Camille will add pictures later on.

- After setting ZM4 into SAFE state we locked all three stages of the suspension. We had already taken healthy TF measurements before starting our work.

- The bottom mass cable was disconnected and carefully re-routed so that it stays away from the fixture plate.

- four add-on masses (basically 1/4-20 screws with washers) attached to the bottom mass was then removed.

- bottom mass Fixture plate (D2100121) was attached to the structure using six 8-32 screws.

- The bottom mass (already locked using EQ stops) was then further clamped using four 1/4-20 screws through the fixture plate. We had to adjust the height of the bottom mass to the align the threads with the holes on the fixture plate.

- Once the bottom mass was securely clamped, we removed the three set screws on the preloader.

- Using a torque wrench we increased the preload on the bottom mass by ~29 in.lb. (Total preload from torque after increase was 75 in.lb).

- We then followed all the above steps backwards (i.e set screws, add on mass put back, fixture plate removed, cable re-connected and the suspension set free).

- Once all done, we started damping the suspension and checked for any BOSEM flag changes - looked all fine.

- We took the transfer function measurements and ZM4 looked healthy.

Hence we took all the tools out and put the curtains back on HAM7 chamber.

Next, we will go into laser hazard with SQZ team and check for any changes in beam alignment and make adjustments as required.