Evan, Yuta, Stefan, Kiwamu,
As a preparation of ASC for PRMI, we briefly checked the WFS RF chains and then adjusted all the demodulation phases. We didn't attempt to close an ASC loop yet.
RF signal check:
When we checked the RF output from the WFSs, surprisingly we didn't find a reasonable signal at all. It eventually turned out that the REFL was not aligned on the WFSs due to some accidental servo on RM1 and RM2. Anyway, since we were already at the floor with an network analyzer, we went through all the segment by injecting an excitation at the RF test input and measuring the RF output for a sanity check. All the segment looked good and the measurement we got was consistent with what Rich did a long time ago (see alog 8022).
Also, we did the I-Q balance adjustment on a demodulator for REFL_B_RF9 by doing the same test as we did before (see alog 9100) because we haven't adjusted it due to a electronics malfunction. The resultant phase difference is:
H1:ASC-REFL_B_RF9_SEG4_PHASE_D = 88.27
The amplitude of I and Q were differ by 1% which is noticable, but we didn't correct it because in soem future we might change the whitening gain settings which messes up the amplitude balancing.
Adjustment of demod phases:
To have a pure in-phase signal, we excited the IMC length by injecting a 500 Hz sinusoidal signal into the IMC servo board. At the beginning, we had the PRMI locked and used it as a PM-to-AM convertor. However, for some reason, the PRMI doesn't stay locked for a long time at that time. Instead we simply used unintetionally-existing RFAM reflected off of PRM without any interferometer aligned. Of course, the RFAM was off from the true in-phase. Therefore we had to add a correction offset to all the demod phase at the end by using LSC_RF9 and LSC_RF45 since we knew that they were well adjusted for a in-phase signal.
The results are:
After the adjustment, we started shaking PR2 in pitch at 95 Hz. The signals mostly showed up in the Q signals everywhere. We are not certian what this indicates at this point.