Komori, Tanaka
We tried to decrease the sensing noise of the CARM PD which is caused by the jiter to the PD by adjusting the beam centering on CARM PD. We adjusted the offset of IMMT2 PIT ASC (ASC-INP2_P_OFFSET) for this purpose. Fig. 1 show the result. We found that the bumps decreased when the positive offset was applied. So this indicates that the bumps from 300 Hz to 380 Hz in DARM sensitivity may be reduced by CARM PD centering
This post summarizes the work conducted last Friday.
The improvement achieved by setting the offset on ASC-INP2_P_OFFSET has shown high reproducibility during each IFO lock.
Therefore, I have left the offset at +1.0 in the filter bank.
This value will be re-tuned when the optimal input alignment for the IFO changes in the future.
I also attempted to optimize the offset of INP2 yaw but did not observe any significant changes in the DARM sensitivity, so the yaw offset remains at zero.
At this point, we are uncertain whether the improvement is due to better input alignment for the IFO or improved alignment specifically to the CARM PD.
To distinguish between these two effects, it will be useful to adjust the alignment of the mirror right before the CARM PD directly by hand while the IFO is locked, as an initial trial.
If the improvement is found to be related to the alignment of the CARM PD, we can consider installing a pico-motor on that mirror for remote control adjustments.
