Ushiba, Tanaka

We measured the TF from CARM in out-loop sensor (K1:LSC-REFL_PDA3_RF45_I_ERR) to DARM (fig.1). In this time, due to increasing IN1GAIN from ~-20dB to +10B since the previous measurement, we increased the excitation amplitude to ~30dB. The coherence below 200 Hz is low but the excitation amplitude could not be increased due to the DAC limit.

From the TF, we projected the out-loop CARM to DARM. Fig.2 shows the result. Current residual CARM seems not to limit the DARM sensitivity. As for the region below 200 Hz, it shows a kind of the upper limit but does not limit the sensitivity.

On the other hand, the bump around 520 Hz in DARM seems to be caused  by CARM