Decigo japanese space gravitational wave detector
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DECIGO – Japanese Space Gravitational Wave Detector. International Workshop on GPS Meteorology January 17, 2003 @ Tsukuba Center for Institutes Seiji Kawamura* and DECIGO-WG (*) National Astronomical Observatory of Japan. What is Gravitational Wave?.

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DECIGO – Japanese Space Gravitational Wave Detector

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Decigo japanese space gravitational wave detector

DECIGO – Japanese Space Gravitational Wave Detector

International Workshop on GPS Meteorology

January 17, 2003

@ Tsukuba Center for Institutes

Seiji Kawamura* and DECIGO-WG

(*) National Astronomical Observatory of Japan


What is gravitational wave

What is Gravitational Wave?

  • Predicted by A. Einstein in the general relativity

  • Not yet detected directly

  • Emitted by accelerating masses

  • Causing a time-variant tidal strain in space

  • Propagating with the speed of light


Detection of gravitational waves using laser interferometer

Detection of Gravitational Waves Using Laser Interferometer


Longer arm gives larger signals

Longer arm gives larger signals!

Mirror

Shrinking More

Shrinking

Mirror

Extending

Laser

Mirror

Photodetector

Extending More

Laser

Mirror

Photodetector


Large scale gw detectors in the world

GEO (600m)

TAMA (300m)

LIGO (4km)

LCGT (3km)

VIRGO (3km)

LIGO (4km)

AIGO (?km)

Large-scale GW Detectorsin the World


Achievements of tama300

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1

3

1

0

F

e

b

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1

9

9

9

S

e

p

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1

9

9

9

1

0

-

1

5

S

e

p

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2

0

0

0

1

0

-

1

7

J

u

n

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2

0

0

1

1

0

-

1

9

A

u

g

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2

0

0

2

1

0

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2

1

1

0

1

0

0

1

k

1

0

k

1

0

0

k

F

r

e

q

u

e

n

c

y

[

H

z

]

Achievements of TAMA300

2000: World-best sensitivity obtained

2001: World-longest 1000 hours of data obtained


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


Decigo japanese space gravitational wave detector

  • Laser Interferometer Space Antenna

  • Joint Project by NASA and ESA

  • Aiming at 0.1mHz - 100mHz

  • To be launched in 2001

LISA


Gap between terrestrial detectors and lisa

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 bridging the gap

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

  • Completely new sources could be detected

  • Completely new science could be obtained


Gws from inspirals

GWs from Inspirals


What is decigo

10-18

LISA

10-20

Terrestrial Detectors

Strain [Hz-1/2]

(e.g. LCGT)

DECIGO

10-22

(Sensitivity: Arbitrary)

10-24

10-4

102

100

104

10-2

Frequency [Hz]

What is DECIGO?

  • Deci-hertz Interferometer Gravitational Wave Observatory

  • Space Antenna with shorter arm length


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; still primitive


Relationship between sensitivity and arm length

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

Advantages of DECIGO

No confusion limiting noise above 0.1Hz

(From the LISA report)


Acceleration of expansion of the universe

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)

Acceleration of Expansion of the Universe


Ultimate sensitivity of decigo

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

In the Paper, we said…

The ultimate sensitivity of a space antenna in the far future could be, however, 310-27 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

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

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

  • 83 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

  • 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

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.

  • R&D experiments will be started very soon.


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