S. Dwyer, J. Warner, H. Radkins, K. Venkateswara
We did a quick test of sensor correction (SC) along X direction to Stage 1 ISI, previously described in 15146. This attempts to use the ground seismometers located near the test mass chambers in feed-forward like manner to reduce the cavity motion. Sheila and Jim aligned and locked the X-arm using the green laser and data was recorded with SC OFF and ON.
The first pdf shows the signals with SC OFF and the second shows them with SC ON. The signals shown first are the Stage 1 T240s (inertial sensors), the CPSs (positions sensors) and the X arm control signal. The inertial sensors indicate a significant reduction in motion of Stage 1 on both ETMX and ITMX between 50-500 mHz. The microseismic motion is suppressed by factor of ~4. Yet, surprisingly, the X-arm control signal looks almost similar. The oplevs shown on pages 3, 4 indicate that the angular motion of the optics was unchanged so perhaps it might be limiting the control signal.
I 've added a few more lines in to the above plots. In particular, it shows that Ry motion of Stage 1 on both ETMX and ITMX, has large correlation with Pitch of optics. Improvement in angular control of Stage 1 may be needed before longitudinal sensor correction can improve the cavity control signal.