Sheila, Georgia

This morning when we were trying to check the phasing of ASC-REFL_A_RF9 and ASC-REFL_A_RF9 for the ASC loops, we found something was ringing at ~2 Hz. The 2nd DC centering loop - ASC-DC2 - was ringing and railing RM2.

Sheila and I took pitch and yaw transfer functions, templates here:

/ligo/svncommon/IscSVN/iscmodeling/trunk/ALIGOH1/ASC_loops/Measurements/DC_centering

We found the current filters to be suboptimal, and made and implemented a new filter. The new filter, “ctrl", has a pair of 1.5Hz poles just below the suspension resonance frequency, and a pole at 0.1 Hz. This replaces the "1:300" filter.