On Wednesday 21st of August I measured the residual motion of the optic in ALIGNED state. The motivation of measuring was to compare with the results reported in entry 10067 which were taken on a day a typhoon was in the neighborhood.
Today the weater is favorable. In ALIGNED state the suspension fulfills the requirement.
This table shows the integrated RMS displacement for each degree of freedom and the requirement.
| Degree of freedom | ALIGNED | Requirement | klog 9704 |
| Longitudinal displacement | 0.135 µm | 0.4 µm | 0.16 µm |
| Longitudinal velocity | 0.140 µm/s | 0.5 µm/s | 0.21 µm/s |
| Pitch displacement | 0.066 µrad | 1 µrad | 0.047 µrad |
| Yaw displacement | 0.096 µrad | 1 µrad | 0.060 µrad |
Relevant notes:
- There's no Inertial damping.
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Coherence of the optic motion with the second floor seismometer IXV was estimated. There's high coherence as follows:
- TM-L with seismometer-Y (arm) from 100 mHz up to 1 Hz.
- TM-P with seismometer-Z (vertical direction) from 200 mHz to 400 mHz.
- TM-Y with seismometer-Z from from 200 mHz to 400 mHz.
The mechanism of coupling between ground vertical and optic yaw is not clear. We should check the oplev diagonalization. Nevertheless, it's more likely related to having ferromagnetic connectors in the vicinity of the magnetic damper above the Standard Filter. See entries 5850, 5873, 6927.
Other notes
- Directory: /kagra/Dropbox/Subsystems/VIS/TypeBData/SRM/Noise/Measurements/20190821/
- File for ALIGNED state: SRM_ALIGNED_TM_OPLEV_ASD_190821_1565940969.xml
- Bandwidth of the displacement measurement' from 0.010 Hz to 800 Hz.
- The bandwidth of the optic velocity measurement was from 0.010 Hz to 10 Hz. Above 10 Hz there is a lot of noise which I don't believe is real displacement of the optic. The peaks are likely related to the oplev optics support platform
- Related entries: 9704.
