Seb, Terra
Thanks to Craig and Dan's dedicated locking efforts last night, we've measured a full suite of test mass mechanical mode Qs post all AMDs. Results here. We see reduction of Q for all modes above 9kHz; 15 kHz modes see reduction factors of at least factor of 10. Measurements done at 2 W input power for least parametric gain contribution and consistency with the few pre-AMD measurements we have.
Reminder that parametric gain Rm ~ QmParm where Qm is quality factor of the mechanical mode, Parm is the power in the arm cavity, Rm > 1 is unstable. In the attached table, we note pre-AMD Qs from what measurements I could find quickly from the last two years. The last column shows predicted Qs from sec 4.11 in Seb's thesis (note these differ from the predicted Q's in 38129 as the latter were before a change in the modeling of the epoxy layer realized after the results of the ETMX AMD test). I also attach the modeled max parametric gains at Parm = 750 kW pre and post AMDs from Seb's thesis to give some context.
To check if modes at 23kHz are aliased, we checked the frequency shift over a 4 hour lock and all but one look to be not aliased (they slightly increased in freq along with drumhead modes).
We have a few anomalies/poor fits that we'll try to remeasure in the next few nights.
