I estimated the Q-values of the roll, pitch, and vertical modes of the four test masses, corresponding to theQ-values of the sapphire blade springs, by ringdown measurement.
The results are presented in the attached figures (Fig. 1: roll, Fig. 2: vertical, Fig. 3: pitch) and summarized in the following list.
| Roll | Vertical | Pitch | ||||
| Resonance | Q-value | Resonance | Q-value | Resonance | Q-value | |
| ETMX | 22.812 Hz | 8.1e3 | 9.484 Hz | 3.3e3 | 7.410 Hz | 3.4e3 |
| ETMY | 22.699 Hz | 7.2e3 | 10.413 Hz | 3.5e3 | 7.425 Hz | 3.8e3 |
| ITMX | 22.689 Hz | 8.8e3 | 9.965 Hz | 3.7e3 | 7.343 Hz | 3.2e3 |
| ITMY | 22.953 Hz | 8.5e3 | 9.686 Hz | 3.0e3 | 7.416 Hz | 1.2e3 |
The estimation errors for the resonant frequency and the Q-value are 2 mHz and 0.1e3, respectively.
The Q-value of the IY pitch mode is significantly smaller than the others.
All the measured Q-values are lower than the designed values, indicating the need for improvements to achieve the design sensitivity.
