jeffrey.kissel@LIGO.ORG - posted 08:30, Tuesday 11 March 2025 - last comment - 09:42, Tuesday 11 March 2025(83288)
PR3 Optical Lever QPD AA Cable Moved from SUS-C4 U11 D9 Port 7 to SUS-C4 U32 D9 Port 8
J. Kissel ECR E1700228 WP 12370 I've executed the PR3 Optical Lever QPD AA Cable move from SUS-C4 U11 D9 Port 7 to SUS-C4 U32 D9 Port 8 described in more detail a few days ago (LHO:83168) in order to make room for the incoming PM1 (per ). See LHO:83168 for "before" pictures; I attach "after" pictures here: - 2025-03-11_SUS-C4_PR3OplevMove_U11_AAChassis_After_1 shows that D9 port 7 and 8 of U11 AA chassis are now vacant, - 2025-03-11_SUS-C4_PR3OplevMove_U11_AAChassis_After_2.jpg shows that this AA chassis is serial number S1202339. - 2025-03-11_SUS-C4_PR3OplevMove_U32_AAChassis_After_1.jpg shows the big-picture scene around U32 AA chassis, - 2025-03-11_SUS-C4_PR3OplevMove_U32_AAChassis_After_2.jpg shows the cable, "H1:OP LEV_PR3_AA" or "H1:SUS-HAM2_88" specifically, connected into to U32 AA chassis D9 port 8, the last "IN29-31," spigot of this AA chassis that supports sush2a's ADC1. - 2025-03-11_SUS-C4_PR3OplevMove_U32_AAChassis_After_3.jpg shows that this U32 AA chassis is serial number S1202340
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Proof that (after we restored the alignment offsets at the M1 stage) PR3 optical gross function has returned. From the trends alone, I see that - the pitch signal is a bit noisier, maybe 0.1 [urad] more RMS. - the yaw signal is drifting slowly at a super small slow 0.02 [urad/minute]. The total SUM of the QPD segments have returned to the identical value tho. Will gather more data, e.g. ASD, to confirm if, and at what frequency, the performance is worse in pitch. Will wait patiently in yaw to see if the trend is something interesting or some transient that doesn't matter. I suspect that this change in character won't matter at all. Recall we DO NOT use the PR3 optical lever for any controls, only for monitoring and driven characterization.
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Here's a look at the amplitude spectral density of the PITCH and YAW signals before and after the change.
In short: No concern -- the optical lever performance is equivalent as before
Also -- hidden beneath the comparison of
"read out by U11 AA chassis, ADC0 of sush2b, then shipped over to sush2a via IPC to be processed by PR3 model"
vs.
"read out by U32 AA chassis, ADC1 of sush2a, directly processed by PR3 model"
is that the "after" time period is during maintenance day when site-wide sensor correction is turned OFF.
So, the only substantial change in performance (and the increase in RMS I mentioned in the above LHO:83290) is in PITCH but it's because sensor correction is now off, vs. the before data both in the trends and the reference traces here where it was on.
(Good job sensor correction!)
Also in pitch, there's a bit of broadband increase in noise between 5 and 20 Hz, but this may be where the optical lever QPD is ADC noise limited. But also, a slight increase in noise doesn't really matter -- because the optical lever is much noisier compared to the real motion of the suspension. Even during driven measurements, we struggle to get coherence in this region.
There're some minor improvements in character of sharp features in both pitch and yaw above 10 Hz.
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