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takafumi.ushiba - 17:18 Friday 13 December 2024 (32003) Print this report
Ring down Q measurement of V/R/P resonances of Type-A suspension

I excited vertical resonances around 10 Hz (fig1), roll resonances around 22 Hz (fig2), and pitch resonances around 7.5 Hz (fig3) for Q-measurement.
Starting time of ring down and signals, which can be used for Q meaurement, for each suspension are as follows:

ITMX:

2:11:00 UTC: K1:VIS-ITMX_NBDAMP_V2_OUT_DQ
1:41:25 UTC: K1:VIS-ITMX_NBDAMP_R2_OUT_DQ
2:39:10 UTC: K1:VIS-ITMX_NBDAMP_P3_OUT_DQ

ETMX:

2:09:30 UTC: K1:VIS-ETMX_NBDAMP_V2_OUT_DQ
1:42:05 UTC: K1:VIS-ETMX_NBDAMP_R2_OUT_DQ
2:39:45 UTC: K1:VIS-ETMX_NBDAMP_P3_OUT_DQ

ITMY:

2:10:50 UTC: K1:VIS-ITMY_NBDAMP_V2_OUT_DQ
1:42:40 UTC: K1:VIS-ITMY_NBDAMP_R2_OUT_DQ
2:41:05 UTC: K1:VIS-ITMY_NBDAMP_P3_OUT_DQ

ETMY:

2:12:15 UTC: K1:VIS-ETMY_NBDAMP_V2_OUT_DQ
1:42:10 UTC: K1:VIS-ETMY_NBDAMP_R2_OUT_DQ
2:41:30 UTC: K1:VIS-ETMY_NBDAMP_P3_OUT_DQ

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Comments to this report:
tomotada.akutsu - 22:01 Friday 13 December 2024 (32005) Print this report

Thank you for your efforts. The graphs show much averaged signals, but hopefuly they are recorded with proper sampling rate!

kentaro.komori - 23:41 Sunday 15 December 2024 (32009) Print this report

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.

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