Sheila, Hang

During power-ups today we saw some ~0.5 Hz oscillations in DSOFT Pitch that kept causing locklosses. Therefore we copied our CSOFT P setup to DSOFT P to increase its bandwidth. Specifically, we blended in to original DSOFT P signal (a comb of 4 trans QPDs that decouples the TMS drift) another comb of trans QPDs that are insensitive to DHARD. The blending freq is at 0.03 Hz, same as CSOFT. After the blending, for DS P we were able to engage the HBW control filters we used for CS P and pushed the filter bank gain up to 30. We also noticed that the input matrix for DS was a factor of 2 higher than the CS value, thus our current DS P loop should have a BW twice that of CS P, sufficient to damp the 0.5 Hz oscillation.

We have put the new setup in guardian and it seems fine to engage the soft loops with this new config.