Jenne, Carl, Ross

We have been testing some of the filters settings for PI mode damping. During the lock tonight we saw 5 unstable modes at 15009Hz (ETMY), 15522Hz (ITMX), 15541Hz (ETMX) , 15542 (ETMY) and 18038Hz (ETMY). The 15522, 15541 and 15542 modes are all unstable after four hours of the 40 W lock. The other two are unstable temporarily as the thermal transient passes through them.

We have demonstrated that we can get steady state damping of the three unstable modes using either 10 Hz band pass filters or iwave tracking (first plot shows damped state amplitudes). We will leave the it in the 10 hz band pass filter configuration. We also show that we can excite and damp the steady state mode at 15009Hz using a 10 Hz bandpass filter (second plot) which should result in a reduced mode amplitude during the transient. 

We will put these filter settings into the guardian. The ETMX damping will not happen unless the SUS_PI guardian state is manually set to ETMX PI DAMPING.

Between 11 to 12 UTC all four ring heaters were stepped by 0.5W for approximately 15 minutes for test mass mode identification.