Today I took "unbiased" OLGs of SRC1 and SRC2 P and Y (67187). I have plot the measurements with error shading.

For reference, SRC1 controls SRM and is sensed using the AS RF72 WFS (118 MHz-45MHz). SRC2 controls SRM and SR2 and is sensed using the AS_C QPD.

SRC1 P has a UGF around 0.01 Hz (!), with a phase margin of about 90 deg. SRC1 Y is similar, 0.01 Hz UGF and phase margin of 100 deg.

SRC2 P has a UGF around 0.05 Hz with a phase margin of 42 deg. SRC2 Y has a UGF around 0.02 Hz and a phase margin of about 46 deg.

These UGFs are lower than I expected. I remember Gabriele and I targeting UGFs around 100 mHz when reworking the design of these loops. Everything runs fine and we don't seem to have any troubles with the SRC ASC during O4. But if we need more microseism suppression in the SRC, we obviously need to do a redesign. I will make a point to do some analysis soon to determine if we need more suppression of angular motion in that cavity.

These loops are definitely hard to measure and for all four measurements I was only able to get decent coherence up to 0.1 Hz. If I had more time I would run these much longer and attempt to target an even lower frequency measurement. However, the templates are still useful and I saved them with the other ASC templates for future use.

You can find the measurement templates, exported data, and processing code in '/ligo/home/elenna.capote/DRMI_ASC/SRC{1,2}'.

The templates for the these measurements are also saved in [userapps]/asc/h1/templates/SRC{1,2} as 'SRC{1,2}_{P,Y}_olg_broadband_shaped.xml'.

These measurements complete my goal to measure all the ASC loops!