Marc, Michael, Yuhang

On wednesday morning we started the AA characterization.

First, we measured the SNR of one QPD segment (here QPD1_I1) but similar results are expected for other segments.

You can see in figure 1 that we have reasonable SNR up to about 100 Hz.

Then we measured the input opto-mechanical transfer function by injecting white noise in input pitch (amplitude 9000) and yaw (amplitude 6000) and checking the signal reconstructed by the AA.

Note that to make these measurements with diagui we had to close the mirror damp loops.

The results are presented in figure 2 and 3.

Then when we tried to inject noise to end we unlocked the FC.

Actually, even if the damp loops are not used (gain to 0), there were several filters and large offsets that caused issues.

So on Thursday morning I repeated these measurements for end mirror  with identical amplitude without particular troubles.

Next step is to combine these measurements with the filter that we are using to check the bandwidth, UGF, phase margin to see if we can improve the AA filter.