Several point of this loop is:

• The residual motion is < 20 nrad for all mirrors.
• The low UGF is due to the low S/N ratio of GRQPD signals. This ASC loop coexists with the oplev loop, and easy to switch. Once we got good ASC signal e.g. WFS, we can turn the oplev loop of.
• ADS loop is just for the initial alignment. It is not urgent task.
• Oplev signal (attached in Kenta's report) does not seem to be suppressed. However, the TRANS power stability has been improved by this loop as shown in the attached plot. The red and blue curve is the GR TRANS power spectra with and without QPD loop respectively. This indicates that the oplev DC signal doesn't show purely the mirror motion, but the ground motion.