Sheila, Kiwamu,
Our focus tonight were:
- DRMI 3f lock
- DRMI WFS loops
(DRMI 3fs are now stable)
We succeeded in transitioning to the 3f signals in DRMI. We checked the demodulation phase of REFLAIR_RF135 by exciting SRM and BS at a time. A good demod phase was found to be 56 deg while it had been -2.7 deg since the last week (see alog 14268). This demod phase was the one in which the SRCL signal is minimized in 135_Q. The resultant input elements are:
- RF27_I => PRCL = 1.0
- 135_Q => MICH = 0.7
- 135_I => SRCL = 0.3
I have not measured the open loop transfer functions yet, but so far I did not see a gain peaking. The SRM M2 stage coil output had an rms counts of about 1x104 which is very OK in terms of the DAC saturation. I did not get a chance to see its long term stability. The ISC_DRMI guardian is edited accordingly and we confirmed that the guardian could transition to the 3fs automatically. Note that I enabled two whitening stages in REFLAIR_RF135. This saturates the ADC until the DRMI is locked, but once it is locked, the saturation does not seem to happen any more.
(some attempts on ASC loops)
For some reason, the SRCL mode-hop happened frequently tonight, even though the alignment was not too bad -- both PRC and SRC sideband power could fluctuate as small as a few % depending on misalignment which of course evolves on a time scale of order of 10 sec. So we decided to close the ASC loops rather than manually aligning the optics. We started from MICH which is ongoing.
Early in the evening last night we could not lock the input beam to the X arm (because of a maintence day snafu), and skipped this step of our inital alingment. Although the pointing down the arm seemed OK based on the flashes that we saw, it was actually not good. We then tried our inital alingment steps of PRX with refl wfs, which didn't work.
Once we had recovered the ETMX ISI we redid the intial alingment process from the begining, and it worked well resulting in a good alingment for DRMI locking.