Ushiba, Hirose, K. Tanaka

## Abstract

We have successfully done a DC readout of PRFPMI with the ASC for all degrees of freedom except ITMs and OMC. We were able to keep the lock on for about 38 minutes (~19:35 - ~20:05 JST 2023/04/05). We also measured the transfer function of the DARM and confirmed that the optical gain was unchanged compared to the case without ASC.

## What we did

• First, to check whether the previous problem of an offset being applied to the AS RF17 WFS when we applied a DARM offset was reproduced, we applied a DARM offset while we turned off only the ASC with the AS RF17 WFS. We turned on the DC centering control of the ASWFS with the DARM offset and checked whether the offset on the AS RF17 WFS changed. As a result, we observed the small change by the beam position (Fig. 1).
• Once we obtained this result, ASC by ASWFS was turned on for the PRFPMI in the DC readout state, using the offset value on ASWFS as the set point for control by ASWFS. After that, the alignment did not change abruptly, and the PRFPMI could maintain its lock for about 38 minites (Fig. 2). After 38 mins, OMC transmitted power began to oscillate at about 30 Hz and PRFPMI lost the lock.
• We also measured the transfer function of the DARM and confirmed that the optical gain was unchanged compared to the case without ASC. (Fig.3 )