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Performance Measurement of the Prototype Pre-isolator for KAGRA-SAS

JGW-G1200930. Performance Measurement of the Prototype Pre-isolator for KAGRA-SAS. ICRR M2 Takanori Sekiguchi. ICRR, NAOJ A , ERI B , Sannio Univ. C , INFN Roma D , NIKHEF E , AEI F

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Performance Measurement of the Prototype Pre-isolator for KAGRA-SAS

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  1. JGW-G1200930 Performance Measurement of the Prototype Pre-isolator for KAGRA-SAS ICRR M2 TakanoriSekiguchi ICRR, NAOJA, ERIB, SannioUniv.C, INFN RomaD, NIKHEFE, AEIF Ryutaro Takahashi, Kazuhiro Yamamoto, Takashi Uchiyama, HideharuIshizakiA, AkiteruTakamoriB, Riccardo DeSalvoC, EttoreMajoranaD, Eric HennesE, Jo van den BrandE, Alessandro BertoliniE,F, MasatakeOhashi, Kazuaki Kuroda, LCGT Collaboration

  2. Pre-Isolator Role of Pre-Isolator • Top part of KAGRA-SAS • Role of Pre-isolator 1. Vibration Isolation at a low frequency (< 0.1 Hz) * Attenuate the mirror oscillation at the micro-seismic peak (0.2~0.3 Hz) 2. Control the position and orientation of the system The 67th Annual Meeting of JPS

  3. Schematic View of Pre-Isolator ~1.2 m GASFilter ・Vertical attenuation InvertedPendulum ・Horizontal attenuation Position Sensor(LVDT) Coil-magnet actuator Accelerometer The 67th Annual Meeting of JPS

  4. Pre-Isolator Prototype @Kashiwa, ICRR GASFilter Inverted Pendulum The 67th Annual Meeting of JPS

  5. About this Presentation • Performance measurement of GAS Filter, vertical LVDT, coil-magnet actuator The 67th Annual Meeting of JPS

  6. Geometric Anti-Spring (GAS) Filter • Radially arrangedcantilever springs • The horizontal force works as an anti-spring and reduces the resonant frequency of the filter • In principle the frequency can be reducedto zero. Restoring force Compression Anti-spring force The 67th Annual Meeting of JPS

  7. Resonant Frequency Measurement • The resonant frequency of the filter is measured, tuning the load weight and the blade compression. • Using Mercury 2000(MicroEsystems) as a displacement sensor Photo sensor Load ~320 kg Scale The 67th Annual Meeting of JPS

  8. Resonant Frequency Measurement Load Increases The 67th Annual Meeting of JPS

  9. LVDT (Linear Variable Differential Transducer) • Non-touching displacement sensor • 10 kHz modulation • The voltage induced at the two receiver coils depends on the position of the primary coil. The 67th Annual Meeting of JPS

  10. LVDT Calibration Micrometer Residual [mV] The 67th Annual Meeting of JPS

  11. LVDTNoise Spectrum • As sensitive as TAMA-LVDT • Limited by the noise from the electric circuit (driver) ~100 nm/rtHz @ 1 - 50 Hz The 67th Annual Meeting of JPS

  12. Force Transfer Function LVDT Coil-Magnet Actuator • Random input signal to the actuator • Transfer function from the actuation force to the LVDT signal • With the digital system ∝f-2 The 67th Annual Meeting of JPS

  13. Non-Linear Response • When the actuator is driven by a high frequency signal (> 2 Hz), the LVDT shows a non-linear response. • The same phenomenon is observed even when the magnet for the actuator is eliminated. • Magnetic field couplings?? Actuator Input Signal LVDT Output The 67th Annual Meeting of JPS

  14. Summary, Future Works • Performance measurement on the GAS filter, LVDTand actuator of the pre-isolator prototype • The top filter can be tuned at ~ 0.2 Hz, and maybe even lower. • The linear signal is observed in LVDT over a range of ~1 cm. • Non-linear couplings between the actuator and LVDT. • Tuning the top filter at lower than 0.1 Hz, and the Q-factor, hysteresis, stability are checked. • Investigating the cause of the actuator-LVDT couplings • Control test with the inverted pendulums The 67th Annual Meeting of JPS

  15. End The 67th Annual Meeting of JPS

  16. Appendix The 67th Annual Meeting of JPS

  17. Q-factor Measurement Chunk 1 • Divide a ring-down signal to many chunks. The signal in each chunk is fit by the following function Chunk 2 Chunk 3 Chunk 4 • Investigating amplitude (A) dependence of the Q-factor (Q=π*f*τ) The 67th Annual Meeting of JPS

  18. Q-factor Measurement • Q-factor increases when the amplitude decreases • Explained by the dissipation controlled by Self-Organized Criticality (SOC) The 67th Annual Meeting of JPS

  19. Displacement Sensor • Linear encoderMercury 2000 (MicroEsystems) • Resolution: 80 nm Photosensor Scale The 67th Annual Meeting of JPS

  20. Force Transfer Function The 67th Annual Meeting of JPS

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