M.Yamamoto,Sato,and Tanaka

Date of measurement : 2023/2/2

In FPMI lock,We excited elastic vibration resonances in ITMX and measured their peaks and Q-values.

In this measurement, resonance of two elastic vibration modes was confirmed.

Procedure

To excite the elastic vibration of the ITMX, An excitation signal was input to the drive port of the high power coil driver of Test Mass stage of the ITMX.

The excitation signal was injected from moku.lab as an analog signal.

The elastic vibration signal was measured from test ports in the Common path of CARM Common Mode Servo  with FFT analizer and lock in amplifer.

(We also tried to get a signal from AS RFPD, but that did not work.).

Result

A resonance signal was confirmed at 23.65325 kHz and 34.3927 kHz.

Also, the decay time of the excitation signal indicated that

 at 23.65325 kHz

 the time constant is 0.49 seconds and Q-value is 3.5×10^4.

at 34.3927 kHz

 the time constant is 0.15 seconds and Q-value is 1.6×10^4.

(Each measurement was taken twice, and the time constant is shown as the average of the two measurements.)

Attachment

1.Damping graph at resonance frequency of 23.65325 kHz.

2.Damping graph at resonance frequency of 34.3927 kHz.

3. semilog graph with fitting of 23.65325 kHz.

4. semilog graph with fitting of 34.3927 kHz.