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 Ryutaro Takahashi, Kazuhiro Yamamoto, Takashi Uchiyama, Hideharu Ishizaki A , Akiteru Takamori B , Riccardo DeSalvo C , Ettore Majorana D , Eric Hennes E , Jo van den Brand E , Alessandro Bertolini E,F , Masatake Ohashi, Kazuaki Kuroda, LCGT Collaboration JGW-G1200930
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ICRR M2 Takanori Sekiguchi ICRR, NAOJ A, ERI B, Sannio Univ. C, INFN Roma D, NIKHEF E, AEI F Ryutaro Takahashi, Kazuhiro Yamamoto, Takashi Uchiyama, Hideharu.
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Performance Measurement of the
Prototype Pre-isolator for KAGRA-SASICRR M2 Takanori Sekiguchi
MajoranaD, Eric HennesE, Jo van den BrandE, Alessandro BertoliniE,F, Masatake Ohashi, Kazuaki Kuroda, LCGT Collaboration
JGW-G1200930
Role of Pre-Isolator
2012/3/24The 67th Annual Meeting of
JPS2
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
Schematic View of Pre-Isolator
2012/3/24The 67th Annual Meeting of
JPS3
GAS Filter・ Vertical attenuation
Inverted Pendulum・ Horizontal attenuation
Position Sensor (LVDT)
Coil-magnet actuator
~1.2 m
Accelerometer
Pre-Isolator Prototype
2012/3/24The 67th Annual Meeting of
JPS4
GAS Filter
Inverted Pendulum
@Kashiwa, ICRR
About this Presentation
2012/3/24The 67th Annual Meeting of
JPS5
Performance measurement of GAS Filter, vertical LVDT, coil-magnet actuator
Geometric Anti-Spring (GAS) Filter
2012/3/24The 67th Annual Meeting of
JPS6
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
Resonant Frequency Measurement
2012/3/24The 67th Annual Meeting of
JPS7
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
Resonant Frequency Measurement
2012/3/24The 67th Annual Meeting of
JPS8
Load Increases
LVDT (Linear Variable Differential Transducer)
2012/3/24The 67th Annual Meeting of
JPS9
Non-touching displacement sensor
10 kHz modulation
The voltage induced at the two receiver coils depends on the position of the primary coil.
LVDT Calibration
2012/3/24The 67th Annual Meeting of
JPS10
Micrometer
Res
idu
al [
mV
]
LVDT Noise Spectrum
2012/3/24The 67th Annual Meeting of
JPS11
~100 nm/rtHz @ 1 - 50 Hz
As sensitive as TAMA-LVDT
Limited by the noise from the electric circuit (driver)
Force Transfer Function
2012/3/24The 67th Annual Meeting of
JPS12
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
Non-Linear Response
2012/3/24The 67th Annual Meeting of
JPS13
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??
Summary, Future Works
2012/3/24The 67th Annual Meeting of
JPS14
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
END
2012/3/24The 67th Annual Meeting of
JPS15
APPENDIX
2012/3/24The 67th Annual Meeting of
JPS16
Q-factor Measurement
2012/3/24The 67th Annual Meeting of
JPS17
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)
Q-factor Measurement
2012/3/24The 67th Annual Meeting of
JPS18
Q-factor increases when the amplitude decreases
Explained by the dissipation controlled by Self-Organized Criticality (SOC)
Displacement Sensor
2012/3/24The 67th Annual Meeting of
JPS19
Linear encoder Mercury 2000 (Micro E systems) Resolution: 80 nm