M.Yamamoto,K.Yamamoto,Sato,and Tanaka

We excited the drumhead mode of ETMX and measured its decay time.

We sent the 23.69 kHz beacon signal from function generator nearby the OMC rack to ETMX.
And We connected spectrum analyzer to test ports in the Common path of CARM Common Mode Servo and

measured the spectra of the CARM signal to check whether there was a peak of the beacon in the CARM signal.
We confirmed the peak of the resonance at 23691.175 Hz. The width of the resonance was approximately 0.2 Hz.
We also measured the time variation of the peak voltage with a lock-in amp(time constant: 50 ms) and a data logger .
The signal decayed after the drumhead excitation signal was turned off. From the fitting, the decay time was identified to be 2.8s.
From the ring-down method, the Q value of ETMX was estimated to be 2.1 x 10^5.