After relocking the RefCav in the optics labs at the nominal settings from early yesterday, and tweaking the servo settings (UGF ~170 kHz!).

I took an SR785 spectrum of the RefCav transmitted beam and the ~2.6 Hz resonance is clearly visible. After turning off the HEPA filters, they dropping in amplitude, but a 4Hz spike appears.

The RefCav table has its HEPA filters turned OFF, hope that is ok.

Data will follow shortly.