Reports until 15:57, Tuesday 14 March 2017
H1 SUS (CAL, ISC)
jeffrey.kissel@LIGO.ORG - posted 15:57, Tuesday 14 March 2017 (34824)
Charge Measurement Update; ETMX is Great. ETMY Needs Bias Flipped
J. Kissel, B. Weaver

I attach the the usual year's trend of effective bias voltage accumulated from charge, where the last few weeks are new data points. We expect and hope the trend of effective to be hovering between +/- 10 [V], which keeps the relative actuation strength change to under a few percent.

We see that ETMX looks great in all quadrants. This is likely because our nominal low-noise (NLN) duty cycle is so high -- when in NLN, we turn OFF the ETMX ESD, so it does not have a ~400 [V] on to attract stray charge.

Conversely, because the NLN duty cycle is so high, ETMY is starting to accumulate a significant amount of effective bias voltage. Although we've been flipping the sign of the bias voltage every time we're not using the ETMY ESD, that's "unfortunately" only 10-15% of the time these days with our awesome duty cycle. We should consider flipping sign of the bias voltage we use for ETMY in NLN soon. 

Perhaps the calibration group can take this opportunity to create a new calibration epoch, and reduce the reference time coupled cavity pole frequency...
Images attached to this report