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Bridging the Gap between Terrestrial Detectors and LISA. Elba 2002 May 24, 2002 Seiji Kawamura National Astronomical Observatory of Japan. Contents. Introduction What is DECIGO ? Science obtained by DECIGO Sensitivity of DECIGO Current Status of DECIGO Summary. 10 -18. 10 -20. - PowerPoint PPT Presentation
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Bridging the Gap between Terrestrial Detectors and LISA
Elba 2002
May 24, 2002
Seiji Kawamura
National Astronomical Observatory of Japan
Contents
1. Introduction
2. What is DECIGO?
3. Science obtained by DECIGO
4. Sensitivity of DECIGO
5. Current Status of DECIGO
6. Summary
Gap between Terrestrial Detectors and LISA
10-18
10-24
10-22
10-20
10-4 10410210010-2
Frequency [Hz]
Str
ain
[H
z-1/2] LISA
Terrestrial Detectors(e.g. LCGT)Gap
Importance of Bridgingthe Gap
New window brings new science! Observe inspiral sources that have moved abov
e the LISA band Observe inspiral sources that have not yet mov
ed into the ground-based detector band Completely new sources could be detected Completely new science could be obtained
How to bridge the gap?
Improve the low-frequency sensitivity of terrestrial detectors
Improve the high-frequency sensitivity of LISA
Build a detector suitable for the gap frequency DECIGO
What is DECIGO? Deci-hertz Interferometer Gravitational Wave Observatory Space Antenna with short arm length
10-18
10-24
10-22
10-20
10-4 10410210010-2
Frequency [Hz]
Str
ain
[H
z-1/2] LISA
Terrestrial Detectors(e.g. LCGT)
DECIGO(Sensitivity: Arbitrary)
DECIGO
Named by T. Nakamura in the PRL paper by N. Seto, S. Kawamura, and T. Nakamura
Potential candidate for the future Japanese space antenna
Study of DECIGO just started; still primitive
Relationship between Sensitivity and Arm Length
10-18
10-21
10-19
10-20
Frequency [Hz]
Str
ain
[H
z-1/2] LISA
10-4 10210010-2
DECIGO
Shot Noise (f<f0): XSN/L P∝ -1/2/L (L∝ -2) -1/2/L=L/L
(Arm Length:
x100
f0 f01/100 of LISA)
Force Noise:
x100
XFN/L 1/L∝ f0:1/L
f1f-2
Advantages of DECIGONo confusion limiting noise above 0.1Hz
(From the LISA report)
Acceleration of Expansion of the Universe
NS-NS (z~1)
GW
DECIGO
Output
Expansion + Acceleration?
Time
Str
ain
Template (No Acceleration)
Real Signal ?Phase Delay~ 1sec (10 years)
Seto, Kawamura, Nakamura, PRL 87, 221103 (2001)
Ultimate Sensitivity of DECIGO
Frequency [Hz]10-4 10410210010-2
Str
ain
[H
z-1/2]
LISATerrestrial Detectors(e.g. LCGT)
Ultimate DECIGO
10-18
10-24
10-22
10-20
10-26 M=100kg, L=5×108m)(Quantum noise limited
DECIGO(LISA Technology
L=5×107m)
Ultimate DECIGO × 1000(Necessary for
acceleration measurement)
In the Paper, we said… The ultimate sensitivity of a space antenna in th
e 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.
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 Solve confusion limiting noise problem
DECIGO Working Group
NAOJ does not have a definitive plan after ALMA.
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 To be discussed in the 2nd Symposium (June 4-
5, 2002) for NAOJ future projects
Summary It is important to bridge the gap between
terrestrial detectors and LISA. DECIGO is a candidate for the Japanese space
antenna. There is no WD-WD confusion limiting noise
above 0.1 Hz. DECIGO could measure the acceleration of
expansion of the Universe. DECIGO-WG has just started investigating the
possibility.
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