JGW-G1200930 ICRR M2 Takanori Sekiguchi ICRR, NAOJA, ERIB, Sannio Univ.C, INFN RomaD, NIKHEFE, AEIF Ryutaro Takahashi, Kazuhiro Yamamoto, Takashi Uchiyama, Hideharu IshizakiA, Akiteru TakamoriB, Riccardo DeSalvoC, Ettore MajoranaD, Eric HennesE, Jo van den BrandE, Alessandro BertoliniE,F, Masatake Ohashi, Kazuaki Kuroda, LCGT Collaboration 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 microseismic peak (0.2~0.3 Hz) 2. Control the position and orientation of the system 2012/3/24 The 67th Annual Meeting of JPS 2 ~1.2 m GAS Filter ・Vertical attenuation Inverted Pendulum ・Horizontal attenuation Position Sensor (LVDT) Coil-magnet actuator Accelerometer 2012/3/24 The 67th Annual Meeting of JPS 3 GAS Filter Inverted Pendulum 2012/3/24 The 67th Annual Meeting of JPS 4 Performance measurement of GAS Filter, vertical LVDT, coil-magnet actuator 2012/3/24 The 67th Annual Meeting of JPS 5 Radially arranged cantilever springs The horizontal force works as an antispring and reduces the resonant frequency of the filter In principle the frequency can be reduced to zero. Restoring force Compression Anti-spring force 2012/3/24 The 67th Annual Meeting of JPS 6 The resonant frequency of the filter is measured, tuning the load weight and the blade compression. Using Mercury 2000 (MicroE systems) as a displacement sensor Photo sensor Load ~320 kg Scale 2012/3/24 The 67th Annual Meeting of JPS 7 Load Increases 2012/3/24 The 67th Annual Meeting of JPS 8 Non-touching displacement sensor 10 kHz modulation The voltage induced at the two receiver coils depends on the position of the primary coil. 2012/3/24 The 67th Annual Meeting of JPS 9 Residual [mV] Micrometer 2012/3/24 The 67th Annual Meeting of JPS 10 ~100 nm/rtHz @ 1 - 50 Hz 2012/3/24 As sensitive as TAMALVDT Limited by the noise from the electric circuit (driver) The 67th Annual Meeting of JPS 11 LVDT Coil-Magnet Actuator Random input signal to the actuator Transfer function from the actuation force to the LVDT signal With the digital system 2012/3/24 ∝f-2 The 67th Annual Meeting of JPS 12 When the actuator is driven by a high frequency signal (> 2 Hz), the LVDT shows a non-linear response. Actuator Input Signal The same phenomenon is observed even when the magnet for the actuator is eliminated. LVDT Output Magnetic field couplings?? 2012/3/24 The 67th Annual Meeting of JPS 13 Performance measurement on the GAS filter, LVDT and 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 2012/3/24 The 67th Annual Meeting of JPS 14 2012/3/24 The 67th Annual Meeting of JPS 15 2012/3/24 The 67th Annual Meeting of JPS 16 Divide a ring-down signal to many chunks. The signal in each chunk is fit by the following function Chunk 1 Chunk 2 Chunk 3 Chunk 4 y A exp(t / ) sin(2ft 0 ) Investigating amplitude (A) dependence of the Q-factor (Q=π*f*τ) 2012/3/24 The 67th Annual Meeting of JPS 17 Q-factor increases when the amplitude decreases Explained by the dissipation controlled by Self-Organized Criticality (SOC) 2012/3/24 The 67th Annual Meeting of JPS 18 Linear encoder Mercury 2000 (Micro E systems) Resolution: 80 nm Photosensor Scale 2012/3/24 The 67th Annual Meeting of JPS 19 2012/3/24 The 67th Annual Meeting of JPS 20
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