Matt, Lisa, Danny, Craig, Hang

=====================================

In the ALIGN_IFO guardian, we created two new states called PREP_MICH_DARK_ALIGN_WFS and MICH_DARK_ALIGN_WFS. These states actively control the MICH alignment when locked with the dark fringe, using WFS signal (AS_B_RF45_I for both pitch and yaw) instead of dithering. It was designed to be used for the contrast defect measurement in the simple mich configuration, as it should minimize the contamination due to misalignment.

We first used this state to measure the contrast defect, and got a large contrast of 3%. See the first image. A 02 mode was clearly visible. Then Danny noticed that the CO2 Y heating was left on (1 W central heating) during this measurement.

We then turned off the central heating and instead put 1 W (~3.8 W delivered) of annular heating on Y. After a while we again locked the MICH in dark with angular control on using the WFS. The dark fringe got improved significantly. We measured ~ 18 ct in AS_A_NSUM the dark state, while in the bright fringe we had ~ 10000 ct. This leads to ~0.2% contrast defect in the simple MICH config. See the second plot for the dark fringe residual beam (note that we modified the exposure time to max in the second image). Also note that we did not follow the entire heating process and we might overshoot in the annular heating. The contrast defect could be further improved.

======================================

We also did some alignment in the corner station.

For SR2, we looked at AS_A_NSUM in single bounce and scanned SR2 in both pitch and yaw. We recorded the edge values where we start to see drops in AS_A_NSUM, and then put SR2 alignment to the middle of those edge values.

For IM4/PR2, we used the INPUT_ALIGN guardian state to align them to XARM. It seemed that guardian state of misaligning ITMY needed to be updated as ITMY beam still showed up in the AS PD even after we requested it to be misaligned. In order for the input ASC loops to work, we needed to manually misalign ITMY by >30 urad in yaw.

The PRX/SRY guardian states did not work properly currently. We could lock PRX in length but the alignment part didn't work. For SRY even the beam looked roundish in the camera, we could not acquire it to be locked in length.