KAGRA Logbook

Dan, Yokozawa, Yuzurihara, Tanaka

## Abstract

We implemented ADS for Yarm IR. However, The normalized IR trans. power reached only ~0.9 even though ADS was engaged. We are not sure of the reason for now (GV b.t.w. EYC and EYT?). We need more investigation. After that, we implemented the ADS for Yarm GR. The normalized GR trans. power reached only ~0.6 maybe because ADS for GR Yarm moved only SR3 and it is necessary to move one more degree of freedom using something like POS pico motor to optimize the alignment. But, currently, we cannot judge if the Yarm cavity alignment is good or not so we stopped this work today.

## what we did

For now, ITMY and ETMY cannot reach each LOCK_ACQUISITION state. But, we need these states to implement ADS. So we temporarily modified each ENGAGE_STRONGDAMP state in each guardian not to engage some unstable damping controls. (We hope VIS folks will modify their control themselves.) Then ITMY and ETMY can reach each LOCK_ACQUISITION state.
After that, we request the YARM guardian to ADS_IR_ARM_ALIGN to control the ITMY and ETMY alignment with ADS. However, ITMY and ETMY alignment seemed to be dithered but their alignment seemed not to move, and Yarm IR trans. power seems not to be changed. Then we realized each INPUT switch of the ISC2OPLEV filter of IY and EY was turned off instead of each INPUT switch. of the LOCK filter was turned on. So we turned on the INPUTs of ISC2OPLEV and turned off the ones of LOCK. Then, ITMY and ETMY alignment started to move, and the trans. power increased. Therefore, their ADSs seem to work well.
We tweaked the BS alignment to center the beam position of ETMY with engaging ADS. After that, the IR trans. power reached only ~0.9 (fig. 1). We are not sure of the reason for now. Since the normalized Xarm trans. power reached ~1.3, the beam clip seems not to occur in the input path up to BS. if the cause of the loss is the clip, it will occur downstream from BS to trans. PD. One possibility is the GV b.t.w. EYC and EYT.
Anyway, we moved the GR Yarm ADS implementation. The GR alignment for the Yarm cavity got bad because the Yarm cavity at that time aligned with the IR input axis. So we tweaked the SR3 alignment to maximize the GR flash. But, we increased the TEM00 flash to only 0.6 with only SR3 adjustment. this value was below the threshold of the lock by the guardian so we decreased the threshold to 0.4. And then, we request the YARM guardian to lock Yarm and engage ADS for GR. It seems to work well and The GR tran. power reached 0.6 (fig. 2). This may be because ADS for GR Yarm moved only SR3 and it is necessary to move one more degree of freedom using something like POS pico motor to optimize the alignment. But, currently, we cannot judge if the Yarm cavity alignment is good or not so we stopped this work today.