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Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO). 7th Gravitational Wave Data Analysis Workshop December 17, 2002 @ International Institute for Advanced Studies, Japan Seiji Kawamura National Astronomical Observatory of Japan. Contents. Introduction What is DECIGO ?
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Deci-hertz Interferometer Gravitational Wave Observatory (DECIGO) 7th Gravitational Wave Data Analysis Workshop December 17, 2002 @ International Institute for Advanced Studies, Japan Seiji Kawamura National Astronomical Observatory of Japan
Contents • Introduction • What is DECIGO? • Science obtained by DECIGO • Sensitivity of DECIGO • Current Statusof DECIGO • Summary
10-18 10-20 10-22 10-24 Gap between Terrestrial Detectors and LISA LISA Terrestrial Detectors Strain [Hz-1/2] (e.g. LCGT) Gap 10-4 102 100 104 10-2 Frequency [Hz]
Importance of Bridgingthe Gap New window brings new science! • Observe inspiral sources that have moved above the LISA band • Observe inspiral sources that have not yet moved into the ground-based detector band • Cosmological background could be detected Seto’s talk • Completely new sources could be detected • Completely new science could be obtained Seto’s talk
10-18 10-20 10-22 10-24 What is DECIGO? • Deci-hertz Interferometer Gravitational Wave Observatory • Space Antenna with shorter arm length LISA Terrestrial Detectors Strain [Hz-1/2] (e.g. LCGT) DECIGO (Sensitivity: Arbitrary) 10-4 102 100 104 10-2 Frequency [Hz]
DECIGO • Named by T. Nakamura in the PRL paper by N. Seto, S. Kawamura, and T. Nakamura • Potential candidate for the future Japanese space GW antenna • Study of DECIGO just started; still primitive
10-18 10-19 10-20 10-21 102 100 10-4 10-2 Relationship between Sensitivity and Arm Length x100 f1 f-2 LISA Strain [Hz-1/2] DECIGO Force Noise: f0 f0:1/L (Arm Length: f0 XFN/L∝1/L 1/100 of LISA) x100 Shot Noise (f<f0): XSN/L∝P-1/2/L∝(L-2) -1/2/L=L/L Frequency [Hz]
Advantages of DECIGO No confusion limiting noise above 0.1Hz Seto’s Talk (From the LISA report)
Acceleration of Expansion of the Universe Seto’s Talk Expansion+Acceleration? DECIGO GW NS-NS (z~1) Output Template (No Acceleration) Strain Real Signal ? Phase Delay~1sec (10 years) Time Seto, Kawamura, Nakamura, PRL 87, 221103 (2001)
10-18 10-20 10-22 10-24 10-4 102 100 104 10-2 10-26 Ultimate Sensitivity of DECIGO DECIGO (LISA Technology L=5×107m) LISA Terrestrial Detectors (e.g. LCGT) Strain [Hz-1/2] Ultimate DECIGO × 1000 (Necessary for acceleration measurement) Ultimate DECIGO (Quantum noise limited M=100kg, L=5×108m) Frequency [Hz]
In the Paper, we said… The ultimate sensitivity of a space antenna in the far future could be, however, 310-27 around 0.1 Hz in terms of strain, assuming the quantum limit sensitivity for a 100 kg mass and an arm length of 1/10 of LISA.We name this detector DECIGO. This requires an enormous amount of effective laser power, and also requires that the other noise sources, such as gravity gradient noise, thermal noise, practical noise, etc. should be all suppressed below the quantum noise.Here we assume that such an antenna may be available by the end of this century.
Necessary Technologies for DECIGO Three Satellite Formation Flight Solar Radiation Gravity Gradient Drag-free Satellite Deflection of Light Reflection with phase-locking Heterodyne Detection
How to Improve Sensitivity? • Increase effective power - Increase the laser power - Increase the diameter of mirror • Use shorter wavelength? • Reduce other sensing noise • Reduce force noise
DECIGO Working Group • Convened in 2002 as one of WGs to study the future project candidates for NAOJ • 1st Meeting held on May 9, 2002 • 83 members currently involved • R&D experiments to be started very soon
Two R&D Experiments to be Started Very Soon • Collaboration work between NASA-Goddard (LISA) and NAOJ (DECIGO) on ground testing of space interferometry • Constructing a measurement system for Earth environmental monitoring by CRL, Niigata Univ., and NAOJ
Conclusions • It is important to bridge the gap between terrestrial detectors and LISA. • DECIGO is a candidate for the Japanese space GW antenna. • DECIGO-WG has just started investigating the possibility. • Two R&D experiments will be started very soon.