[Ushiba, Hirose]

We were planning to install WFSf3 for ADS on PRMI.

However, the coupling between ALS and WFS QPD was previously reported (klog11180). We investigated how much influence this coupling has.

The lock did not go down when the shutter was open and in the ALS_DARM state and FIND_IR_RESONANCES. The fact that the lock does not go down at this point is probably because there is less coupling than before. However, if the shutter was opened when PRMI_3F_LOCKED, the lock went down. (The ETMX L signal was receiving a signal with a plus/minus of more than 120,000 counts.) FIG1

In the power spectrum, the effect of coupling is almost invisible other than the PRMI_3F_LOCKED when shutter opened. FIG2

As things stand, we think WFSASC with PRMI will be difficult as long as the coupling is large.