Carl, Terra, Rich A.

1. We used the never-before-tested LVLN ITMY ESD driver to ring up and damp two mechanical modes of ITMY, 15072 Hz and 14979 Hz. Below is the amplitude evolution of the 15072 Hz peak as we rang it up, allowed it to ring down naturally, rang it up again, and then damped it down fully with a gain sign flip. 

We drove and damped similarly for the 14979 Hz peak. 15072 Hz is the vertical differential drumhead mechanical mode; 14979 Hz is the horizontal version. For both cases, we tightly bandpassed the H1:OMC-PI_DCPD_64KZ_A/B signal, added a +60deg damping filter, and added gain to the damping filter until saturation. Positive gain drove up, negative damped down. 

I've fit the natural ring down with f(x) = a * exp(bx), where tau = - (1/b). Then Q = pi * 15072 * tau = 31.5 million.

2. Interestingly, we realized after the above tests that we had not turned the ESD bias on for either ITM. After turning on both to 100K cts (to DC offset), we just had time to ring back up the ITMY 15072 Hz mode before a lockloss. Below is a comparison of the ring ups (note we lost lock and did not damp for the ring down portion below). Green trace is the 15072 Hz ring up without bias, blue trace is with bias (time shifted for ease of comparison).  

A slight slope difference is visible but we'll look into this more. Thoughts are that we could use the difference in responses to measure test mass charge coefficients as discussed here and here.

3. We turned ring heaters off and on for future mode-mass identification analysis. For the record (since RH messing with violin modes was a concern tonight):

• 2:36 UTC ETMX RH turned off (ITMX RH was already off)
• 3:00 UTC ETMY RH turned off (ITMY RH was already off)
• 3:32 UTC ITMX RH turned on (0.5 W top and bottom)
• 4:03 UTC ITMY RH turned on (0.5 W top and bottom), ITMX RH turned off
• 4:39 UTC ITMY RH turned off
• 5:56 UTC both ETM RHs turned on (0.5 W top and bottom)