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Performance Measurement of the
Prototype Pre-isolator for KAGRA-SASICRR 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
JGW-G1200930
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Role of Pre-Isolator
2012/3/24 The 67th Annual Meeting of JPS 2
Top part of KAGRA-SAS
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
Role of Pre-isolator
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Schematic View of Pre-Isolator
2012/3/24 The 67th Annual Meeting of JPS 3
GAS Filter・ Vertical attenuation
Inverted Pendulum・ Horizontal attenuation
Position Sensor (LVDT)Coil-magnet actuator
~1.2 m
Accelerometer
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Pre-Isolator Prototype
2012/3/24 The 67th Annual Meeting of JPS 4
GAS Filter
Inverted Pendulum
@Kashiwa, ICRR
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About this Presentation
2012/3/24 The 67th Annual Meeting of JPS 5
Performance measurement of GAS Filter, vertical LVDT, coil-magnet actuator
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Geometric Anti-Spring (GAS) Filter
2012/3/24 The 67th Annual Meeting of JPS 6
Radially arranged cantilever springs
The horizontal force works as an anti-spring and reduces the resonant frequency of the filter
In principle the frequency can be reduced to zero.
Restoring force
Anti-springforce
Compression
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Resonant Frequency Measurement
2012/3/24 The 67th Annual Meeting of JPS 7
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
Load~320 kg
Photo sensor
Scale
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Resonant Frequency Measurement
2012/3/24 The 67th Annual Meeting of JPS 8
Load Increases
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LVDT (Linear Variable Differential Transducer)
2012/3/24 The 67th Annual Meeting of JPS 9
Non-touching displacement sensor
10 kHz modulation
The voltage induced at the two receiver coils depends on the position of the primary coil.
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LVDT Calibration
2012/3/24 The 67th Annual Meeting of JPS 10
Micrometer
Res
idua
l [m
V]
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LVDT Noise Spectrum
2012/3/24 The 67th Annual Meeting of JPS 11
~100 nm/rtHz @ 1 - 50 Hz
As sensitive as TAMA-LVDT
Limited by the noise from the electric circuit (driver)
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Force Transfer Function
2012/3/24 The 67th Annual Meeting of JPS 12
LVDT
Coil-Magnet Actuator
∝f-2
Random input signal to the actuator
Transfer function from the actuation force to the LVDT signal
With the digital system
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Non-Linear Response
2012/3/24 The 67th Annual Meeting of JPS 13
Actuator Input Signal
LVDT Output
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??
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Summary, Future Works
2012/3/24 The 67th Annual Meeting of JPS 14
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
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END2012/3/24 The 67th Annual Meeting of
JPS 15
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APPENDIX2012/3/24 The 67th Annual Meeting of
JPS 16
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Q-factor Measurement
2012/3/24 The 67th Annual Meeting of JPS 17
Chunk 1Chunk 2
Chunk 3
Chunk 4
Divide a ring-down signal to many chunks. The signal in each chunk is fit by the following function
)2sin()/exp( 0 fttAy
Investigating amplitude (A) dependence of the Q-factor (Q=π*f*τ)
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Q-factor Measurement
2012/3/24 The 67th Annual Meeting of JPS 18
Q-factor increases when the amplitude decreases
Explained by the dissipation controlled by Self-Organized Criticality (SOC)
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Displacement Sensor
2012/3/24 The 67th Annual Meeting of JPS 19
Linear encoder Mercury 2000 (Micro E systems) Resolution: 80 nm
Photosensor
Scale
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Force Transfer Function
2012/3/24 The 67th Annual Meeting of JPS 20