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H1 CAL
jeffrey.kissel@LIGO.ORG - posted 09:50, Wednesday 29 May 2024 (78112)
False Alarm :: OMC DCPD Product of OMC DCPD (Transimpedance) x (Whitening) x (Compensation for Each) Remains the Same -- Just Captured Inductor Thermal Transient Yesterday
J. Kissel 

Remeasured the same remote, DAC-driven measurement of the whole OMC DCPD sensing chain -- the transimpedance amplifier, the whitening chassis, and the front-end compensation for the frequency response of those -- as yesterday, now 24-ish hours after the DCPD transimpedance amplifiers were powered on. 

Finally -- some good news!

As suspected, after the giant inductors thermalized, the low frequency response has restored to the same post-2024-vent ~0.3% magnitude drop below 25 Hz. 
Yesterday, I'd only waited 20 minutes after turning them on when I took the data from LHO:78095.
So -- clearly the thermal time constant for the inductors is longer than 20 minutes!
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