Published on January 3, 2008
Space Gravitational Wave Antenna DECIGO Project: Space Gravitational Wave Antenna DECIGO Project 3rd TAMA Symposium February 7, 2003 @ Institute for Cosmic Ray Research, Japan Seiji Kawamura National Astronomical Observatory of Japan Laser Interferometer in Space: Laser Interferometer in Space Signal increased - Due to longer interaction between GW and light (Cancellation of signals at higher frequencies) Noise reduced - Lower seismic noise and gravity gradient noise Sensitivity improved at lower frequencies LISA: LISA Gap between Terrestrial Detectors and LISA: Gap between Terrestrial Detectors and LISA 10-4 104 102 100 10-2 Frequency [Hz] Strain [Hz-1/2] LISA Terrestrial Detectors (e.g. LCGT) Gap Importance of Bridgingthe Gap: Importance of Bridging the 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 Completely new sources could be detected Completely new science could be obtained What is DECIGO?: What is DECIGO? Deci-hertz Interferometer Gravitational Wave Observatory Space Antenna with shorter arm length 10-4 104 102 100 10-2 Frequency [Hz] Strain [Hz-1/2] LISA Terrestrial Detectors (e.g. LCGT) DECIGO (Sensitivity: Arbitrary) DECIGO: 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 Relationship between Sensitivity and Arm Length: Relationship between Sensitivity and Arm Length Frequency [Hz] Strain [Hz-1/2] LISA DECIGO Shot Noise (f<f0): XSN/L∝P-1/2/L∝(L-2) -1/2/L=L/L (Arm Length: x100 f0 f0 1/100 of LISA) Force Noise: x100 XFN/L∝1/L f0:1/L f1 f-2 Advantages of DECIGO: Advantages of DECIGO No confusion limiting noise above 0.1Hz (From the LISA report) Acceleration of Expansion of the Universe: Acceleration of Expansion of the Universe NS-NS (z～1) GW DECIGO Output Expansion ＋Acceleration? Time Strain Template (No Acceleration) Real Signal ? Phase Delay～1sec (10 years) Seto, Kawamura, Nakamura, PRL 87, 221103 (2001) Ultimate Sensitivity of DECIGO: Ultimate Sensitivity of DECIGO Frequency [Hz] Strain [Hz-1/2] LISA Terrestrial Detectors (e.g. LCGT) Ultimate DECIGO M=100kg, L=5×108m) (Quantum noise limited DECIGO (LISA Technology L=5×107m) Ultimate DECIGO × 1000 (Necessary for acceleration measurement) Necessary Technologies for DECIGO: Necessary Technologies for DECIGO Solar Radiation Deflection of Light Gravity Gradient Three Satellite Formation Flight Drag-free Satellite Heterodyne Detection Reflection with phase-locking How to Improve Sensitivity?: 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: 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 80+ members currently involved R&D experiments to be started very soon Two R&D Experiments to be Started Very Soon: Two R&D Experiments to be Started Very Soon Constructing a satellite-satellite tracking simulator for Earth environmental monitoring by CRL, Niigata Univ., and NAOJ Collaboration work between NASA-Goddard (LISA), Univ. of Tokyo, and NAOJ on ground test on force noise Conceptual Design of Satellite-Satellite Tracking Simulator: Conceptual Design of Satellite-Satellite Tracking Simulator AOM Photodetector Low Thermal-Expansion Optical Table Length Sensing System Equal Path Lengths (with Delay Line or Optical Fiber Later) Doppler Simulator Angular Perturbation Simulator Displacement Signal Angular Feedback Signal AOM Alignment Sensing System Quadrant Photodetector Laser Frequency Stabilization System Intensity Stabilization System One Idea of Ground Test on Force Noise: One Idea of Ground Test on Force Noise Low Resonant Frequency Low Thermal Noise Good Sensing System Conclusions: 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.