aLIGO LHO Logbook

H1 SQZ

camilla.compton@LIGO.ORG - posted 12:38, Tuesday 19 August 2025 - last comment - 13:23, Friday 22 August 2025(86445)

PSAMS adjustments for SQZ-OMC mode matching

Leo, Jennie, Camilla

Followed setup instructions from 80010, with 75mW injected in the SEED beam, we had 1mW on OPO_IR_PD_DC slightly lower than last time. Also took SQZ_FC to FC_MISALIGNED. And opened SQZ beam divertor and fast shutter. Have counts of ~60 on ASC-AS_A and B and 7e-4 on ASC-OMC-A and B NSUMs. Jennie took the OMC PZT down to zero to start and then ran a template userapps/../omc/h1/templates/OMC_scan_sqz_beam.xml.

Repeated mode scans with different ZM PSAMs offsets, the DC centering loops could account for the pitch change for PSAMs, for the extreme PSAMS values, I increased the servo limiter from 85 to 95.

nominal: ZM4 6.0V strain, ZM5 -0.4V strain.
ZM4 9.5V strain, ZM5 -0.6V strain.
ZM4 6.0V strain, ZM5 -4.5V strain. Note that the OMC Pitch QPDs were off around -0.1
ZM4 6.0V strain, ZM5 -5.3V strain. Note that the OMC Pitch QPDs were off around -0.1
ZM4 9.0V strain, ZM5 2.0V strain
ZM4 3.0V strain, ZM5 2.0V strain
ZM4 8.0V strain, ZM5 -2.0V strain. Note that the OMC Pitch QPDs were off around -0.1
ZM4 4.0V strain, ZM5 -2.0V strain.
ZM4 9.5V strain, ZM5 -5.0V strain. Realized OMC ASC had been off before this measurement (we had turned it on but them changed OMC GRD which turned it off again)
Repeat of ZM4 9.5V strain, ZM5 -0.6V strain with OMC ASC on.

Jennie and Leo have the data to analyze.

Comments related to this report

jennifer.wright@LIGO.ORG - 17:42, Tuesday 19 August 2025 (86467)

Link

See the ndscope with the channels we used to monitor attached.

This template is saved in /ligo/home/jennifer.wright/Documents/OMC_scan/20250819_SQZ_beam_scan_with_ZM_changes.yaml

leendert.schrader@LIGO.ORG - 15:10, Wednesday 20 August 2025 (86485)

Link

Following up on these OMC scans: attached is the table with all computed mode-mismatch values.

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Mode_mismatch_at_OMC.pdf

leendert.schrader@LIGO.ORG - 13:23, Friday 22 August 2025 (86520)

Link

Leo, Jennie W., Camilla

Below is a plot of the OMC scans fitted with a surface polynomial.
The plot is from the presentation in T2500228, so the labels on axes will be different.
This can be plotted on Matlab simply using the following code block (requires Curve Fitting Toolbox to use fit()).

OMCX = [5.5, 4, 2.3, 3, 8.1, 2.3, 2.3, 6, 9.5, 6, 6, 9, 3, 8, 4, 9.5, 9.5];
OMCY = [-0.8, 0.34, 0.2, 0.85, -0.4, -0.1, 0.2,    -0.4, -0.6, -4.5, -5.3, 2, 2, -2, -2, -5, -0.6];
OMCdata = [1-4.048/100, 1-3.412/100, 1-3.074/100, 1-3.234/100, 1-5.073/100, ...
        1-3.176/100, 1-2.884/100, 1-2.174/100, 1-3.343/100, 1-9.490/100, 1-11.865/100, 1-6.282/100, 1-2.313/100, ...
        1-3.013/100, 1-3.021/100, 1-9.179/100, 1-3.243/100];

omc = fit([transpose(OMCX), transpose(OMCY)], transpose(OMCdata), 'poly22');
    
p = plot(omc);

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