[Nakano,Capote]

Once we achieved a decent PRFPMI RF lock alignment, we opened the WFS shutters. We turned on the centering servos for the REFL, POP and AS WFS (DC3-8). This servo is set at a 0.1 Hz using an integrator, and some gains. The filters in use are FM5, 6, 7 and 9. Once the centering loops were on, we watched the segment signals of the QPDs and determined that they all balanced themselves as expected, indicating the beams were properly centered.

Then, we looked at the whitening gain in place on the WFS. We have engaged 3 stages of whitening for POP and AS with a gain of 15 dB for POP and 12 dB for AS. For REFL we engaged 2 stages of whitening and 6 dB of gain. There is much more light at REFL, so we have to use less whitening and gain overall to avoid ADC overflow. We plan to continue to monitor the ADC overflow warnings to make sure there are no issues with saturation with this new whitening scheme.

The attached plot shows a WFS signal from AS, REFL and POP with the new whitening (blue reference trace) and the previous whitening (red trace). This was measured after the centering servos completed for all dofs.