Download DECIGO

Sora
HEPL Seminar
Feb. 11, 2009 @ Stanford Univ.
Seiji Kawamura
(National Astronomical
Observatory of Japan)
Outline
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Gravitational wave
DECIGO
DECIGO pathfinder
Summary
Appendix
– Displacement noise free interferometer
– Juggling interferometer
Gravitational wave
• Predicted by Einstein
• Emitted from accelerating objects
• Propagates as tidal distortion of space
Distortion of space ~ 10-23
Not yet detected!
GW Sources
• Neutron star / black hole
binaries
• Supernova
• Beginning of the universe
• Etc.
How far (old) can we see?
Beginning of
the universe
GW
10 -43 sec
(Planck
time）
Neutrino
EM
1 sec
(Formation of
380,000 year
Proton, Neutron) (Transparent to13.7 billion year
(Now)
radiation)
Gravitational wave astronomy
Detection of GW
by laser interferometer
Suspended Mirror
Suspended Mirror
Beam splitter
Laser
Detector
Interfering
beam
Mirror
The longer arm length gives
larger signals!
Mirror
Mirror
Laser
Photodetector
Mirror
Laser
Photodetector
Large-scale detectors
LIGO (4 km)
GEO (600 m)
TAMA (300 m)
LCGT (3 km)
CLIO (100 m)
LIGO (4 km)
VIRGO (3 km)
Standard optical configuration
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
• Arm length: 5,000,000km
• Frequency range: 1 mHz - 0.1 Hz
• Target Source: White dwarf binary, Giant BH
coalescence
• Optical configuration: Light transponder
LISA project
What is DECIGO?
Deci-hertz Interferometer Gravitational Wave Observatory
(Kawamura, et al., CQG 23 (2006) S125-S131)
 Bridges the gap between LISA and terrestrial detectors
 Low confusion noise -> Extremely high sensitivity
Strain [Hz-1/2]
10-18
10-20
Terrestrial
detectors
(e.g. LCGT)
LISA
DECIGO
10-22 Confusion
Noise
10-24
10-4
10-2
100
102
Frequency [Hz]
104
Pre-conceptual design
Differential FP interferometer
Arm length: 1000 km
Mirror diameter: 1 m
Laser wavelength：0.532 m
Finesse: 10
Laser power: 10 W
Mirror mass: 100 kg
S/C: drag free
3 interferometers
Arm cavity
Arm cavity
Laser
Photodetector
Drag-free S/C
Mirror
Transponder type
(e.g. LISA)
Why FP cavity?
Shorten
arm length
Implement FP cavity
Strain
Shorten
arm length
Shot noise
Shot noise
Transponder type
(e.g. LISA)
Implement FP cavity
FP cavity type
Frequency
Better bestsensitivity
Drag free and FP cavity:
compatible?
S/C I
S/C II
Mirror
FP cavity and drag free :
compatible?
Relative position
between mirror
and S/C
S/C II
Local
sensor
S/C I
Mirror
Thruster
Thruster
Drag free and FP cavity:
compatible?
Relative position
between mirror
and S/C
S/C II
Local
sensor
No signal
mixture
S/C I
Mirror
Thruster
Thruster
Actuator
Interferometer
output (GW signal)
Orbit and constellation
(preliminary)
Earth
Correlation
for stochastic
background
Record disk
Sun
Increase angular
resolution
Science by DECIGO (1)
10-19
Formation of 10-20
Supermassive BH 10-21
Coalescence
1 cluster
10-22
10-23
Shot noise
10-24
10-25
10-26
10-3
10-2
10-1
1
10
Frequency [Hz]
102
103
Science by DECIGO (2)
10-19
10-20
10-21
5 years
1 cluster
3 months
10-22
10-23
Shot noise
10-24
10-25
10-26
10-3
10-2
10-1
1
10
Frequency [Hz]
Acceleration
of Universe
⇓
Dark energy
Coalescence
102
103
Acceleration of Expansion
of the Universe
Expansion ＋Acceleration?
DECIGO
GW
NS-NS (z～1)
Output
Strain
Template (No Acceleration)
Real Signal ?
Phase Delay～1sec (10 years)
Time
Seto, Kawamura, Nakamura, PRL 87, 221103 (2001)
Science by DECIGO (3)
10-19
10-20
10-21
1 cluster
10-22
10-23
10-24
10-25
Shot noise
Correlation
(3 years)
Inflation
Verification
(GW=210-16)
of inflation 10-26
10-3 10-2 10-1 1
10
Frequency [Hz]
102
103
Requirements

Acceleration noise should be suppressed below
radiation pressure noise
– Force noise: DECIGO = LISA/50
(Acceleration noise in terms of h: 1, Distance: 1/5000, Mass: 100)
– Fluctuation of magnetic field, electric field, gravitational field,
temperature, pressure, etc.

Sensor noise should be suppressed below shot
noise.
– Phase noise: DECIGO = LCGT×10
(Sensor noise in terms of h: 1, storage time: 10)
– Frequency noise, intensity noise, beam jitter, etc.

Thruster system should satisfy range, noise,
bandwidth, and durability.
Roadmap
2007 08
09
10
11
12
13
Mission
R&D
Fabrication
14
15
16
17
18
19
R&D
Fabrication
DICIGO Pathfinder
(DPF)
20
21
22
23
24
25
26
R&D
Fabrication
Pre-DECIGO
DECIGO
Objectives
Test of key technologies
Observation run of GW
Detection of GW w/
minimum spec.
Test FP cavity
between S/C
Full GW astronomy
Scope
1 S/C
1 arm
3 S/C
1 interferometer
3 S/C,
3 interferometer
3 or 4 units
DECIGO Pathfinder (DPF)
DPF
DECIGO
Floating Mirrors
Laser
1,000 km
30 cm
PD
Shrink the arm length
from 1,000 km to 30 cm
Drag-free S/C
Conceptual design and
Technologies to demonstrate
Stabilization
system
Floating mirror
Thruster
Laser
Actuator
Local
Sensor
Drag-free control system
 Laser source and stabilization system
 Control of Fabry-Perot interferometer
 Launch-lock system

–12
1/2
Cavity length: 10cm
Laser: 1064nm, 25mW
Finesse: 100
Mirror mass: 1kg
6
Q–value of a mirror: 10
–12
10
PM
–13
10
Ge
ac
rav
og
–14
10
–15
at
Th
10
ru
–16
rn
ste
10
–17
ois
10
io
n
–2
10
–1
10
–13
10
–14
10
–15
10
–16
No
Laser
Frequency
10
i
La
s
se e
noise
–17
r
pr R
10
es ad
Shot noise
su iat
–18
re ion
M
i
r
10
r
o
no
r therm
al
ise
–19
10
0
1
2
10
10
10
e
–18
10
ce
l er
ity
Noise level [1/Hz ]
10
Frequency [Hz]
1/2
–11
10
Displacement Noise [m/Hz ]
Goal sensitivity of DPF
[kpc, SNR=5]
Observable Range
Expected sources
2
10
BH QNM
BH Inspiral
1
10
Galactic Center
0
10
–1
10
3
10
4
10
5
10
Mass [Msolar ]
6
10
JAXA’s Small science satellite series
• Plan to launch 3 small satellites between 2011
and 2015
– using next-generation solid rocket booster
• Reduce time and cost by means of ‘Standard
bus system’
–
–
–
–
Bus weight : ~ 200kg, Bus power : ~ 800W
Downlink ~ 2Mbps, Data storage ~ 1GByte
3-axes attitude control
SpaceWire-based data processing system
• We submitted a proposal for DPF
In June 2007, I attended the LIGO PAC
meeting at Caltech, and we were invited to
dinner at a Chinese restaurant.
We gained
momentum!
DPF was selected as one of the 4
important mission candidates for
small science satellite series run by
JAXA/ISAS.
DPF S/C
DPF Payload
Size :
900mm cube
Weight : 100kg
Power :
200W
Data Rate: 600kbps
Mission thruster x16
Stabilized Laser
Thruster
Control Unit
Central
Processing Unit
Mission
Thrusters
Housing
Control Unit
Power Supply
SpW Comm.
Interferometer
Module
Satellite Bus
Interfererometer
Control Unit
(‘Standard bus’ system)
Size :
900mm cube
Weight : 200kg
SAP :
800W
Battery:
50AH
Downlink : 2Mpbs
DR:
1GByte
3N Thrusters x 4
Bus Thrusters
Solar Paddle
DPF Mission Outline
Launch: 2012 (target)
Mission Lifetime: 1 year (nominal)
Launcher:
Single launch by M-V follow-on
(solid rocket booster under development)
PBS (Post-Boost stage)
for fine orbit insertion
DPF
500km
Orbit:
Low-Earth (Altitude 500km),
Sun-synchronous orbit (dusk-dawn)
Attitude Control:
Gravity-gradient stab.
Drag-free control with mission thrusters
(Safe hold control by bus thrusters)
History and Future
2006 Nov. Submitted a proposal of DPF
2007 Jun. Fortune cookie
2007 Aug. Selected as a Pre-Phase-A mission
R&D costs funded
2008 Sep. Submitted Phase-A proposal
2008 Dec. Hearing held for selecting the 2nd
mission
2009 Mar. 2nd mission will be selected
Pre-DECIGO
PreDECIGO
DECIGO
Arm length
100 km
1000 km
Mirror diameter
30 cm
1m
Laser wavelength
0.532 m
0.532 m
Finesse
30
10
Laser power
1W
10 W
Mirror mass
30 kg
100 kg
# of interferometers 1
in each cluster
3
# of clusters
4
1
Sensitivity of Pre-DECIGO
S/N~14 for NS-NS@300Mpc, 10-20 events/year
-15
10
Strain sensitivity [1/rHz]
-16
10
DPF
-17
10
-18
10
pre-DECIGO
-19
10
-20
10
NS-NS inspiral (@300Mpc)
-21
10
-22
10
-23
10
DECIGO
-24
10
-3
10
-2
10
-1
10
0
10
1
10
Frequency [Hz]
2
10
3
10
Interim organization
PI: Kawamura (NAOJ)
Deputy: Ando (Kyoto)
Executive Committee
Kawamura (NAOJ), Ando (Kyoto), Seto (NAOJ), Nakamura (Kyoto),
Tsubono (Tokyo), Tanaka (Kyoto), Funaki (ISAS), Numata (Maryland),
Sato (Hosei), Kanda (Osaka city), Takashima (ISAS), Ioka (Kyoto)
Detector
Science, Data
Numata
(Maryland)
Ando (Tokyo)
Tanaka (Kyoto)
Seto (NAOJ)
Kanda (Osaka city)
Pre-DECIGO
Sato (Hosei)
Satellite
Funaki (ISAS)
Design phase
DECIGO pathfinder
Leader: Ando (Kyoto)
Deputy: Takashima (ISAS)
Mission phase
Drag free
Detector
Laser
Housing
Ando
(Kyoto)
Ueda (ILS)
Musya
(ILS)
Sato
(Hosei)
Moriwaki
(Tokyo)
Sakai
(ISAS)
Thruster
Bus
Data
Funaki
(ISAS)
Takashima
(ISAS)
Kanda
(Osaka
city)
DECIGO-WG
Seiji Kawamura, Masaki Ando, Takashi Nakamura, Kimio Tsubono, Naoki Seto, Shuichi Sato, Kenji
Numata, Nobuyuki Kanda, Ikkoh Funaki, Takeshi Takashima, Takahiro Tanaka, Kunihito Ioka,
Kazuhiro Agatsuma, Koh-suke Aoyanagi, Koji Arai, Akito Araya, Hideki Asada, Yoichi Aso, Takeshi
Chiba, Toshikazu Ebisuzaki, Yumiko Ejiri, Motohiro Enoki, Yoshiharu Eriguchi, Masa-Katsu Fujimoto,
Ryuichi Fujita, Mitsuhiro Fukushima, Toshifumi Futamase, Katsuhiko Ganzu, Tomohiro Harada,
Tatsuaki Hashimoto, Kazuhiro Hayama, Wataru Hikida, Yoshiaki Himemoto, Hisashi Hirabayashi,
Takashi Hiramatsu, Feng-Lei Hong, Hideyuki Horisawa, Mizuhiko Hosokawa, Kiyotomo Ichiki,
Takeshi Ikegami, Kaiki T. Inoue, Koji Ishidoshiro, Hideki Ishihara, Takehiko Ishikawa, Hideharu
Ishizaki, Hiroyuki Ito, Yousuke Itoh, Nobuki Kawashima, Fumiko Kawazoe, Naoko Kishimoto, Kenta
Kiuchi, Shiho Kobayashi, Kazunori Kohri, Hiroyuki Koizumi, Yasufumi Kojima, Keiko Kokeyama,
Wataru Kokuyama, Kei Kotake, Yoshihide Kozai, Hideaki Kudoh, Hiroo Kunimori, Hitoshi Kuninaka,
Kazuaki Kuroda, Kei-ichi Maeda, Hideo Matsuhara, Yasushi Mino, Osamu Miyakawa, Shinji Miyoki,
Mutsuko Y. Morimoto, Tomoko Morioka, Toshiyuki Morisawa, Shigenori Moriwaki, Shinji Mukohyama,
Mitsuru Musha, Shigeo Nagano, Isao Naito, Kouji Nakamura, Hiroyuki Nakano, Kenichi Nakao,
Shinichi Nakasuka, Yoshinori Nakayama, Kazuhiro Nakazawa, Erina Nishida, Kazutaka Nishiyama,
Atsushi Nishizawa, Yoshito Niwa, Yoshiyuki Obuchi, Masatake Ohashi, Naoko Ohishi, Masashi
Ohkawa, Norio Okada, Kouji Onozato, Kenichi Oohara, Norichika Sago, Motoyuki Saijo, Masaaki
Sakagami, Shin-ichiro Sakai, Shihori Sakata, Misao Sasaki, Takashi Sato, Masaru Shibata, Hisaaki
Shinkai, Kentaro Somiya, Hajime Sotani, Naoshi Sugiyama, Yudai Suwa, Rieko Suzuki, Hideyuki
Tagoshi, Fuminobu Takahashi, Kakeru Takahashi, Keitaro Takahashi, Ryutaro Takahashi, Ryuichi
Takahashi, Tadayuki Takahashi, Hirotaka Takahashi, Takamori Akiteru, Tadashi Takano, Keisuke
Taniguchi, Atsushi Taruya, Hiroyuki Tashiro, Mitsuru Tokuda, Yasuo Torii, Morio Toyoshima, Shinji
Tsujikawa, Yoshiki Tsunesada, Akitoshi Ueda, Ken-ichi Ueda, Masayoshi Utashima, Yaka
Wakabayashi, Hiroshi Yamakawa, Kazuhiro Yamamoto, Toshitaka Yamazaki, Jun'ichi Yokoyama,
Chul-Moon Yoo, Shijun Yoshida, Taizoh Yoshino
1st International
LISA-DECIGO Workshop
• Nov. 12-13, 2008 @ ISAS, Sagamihara, Japan
• Participants:
– Danzmann, Heinzel, Gianolio, Jennrich, Lobo, McNamara,
Mueller, Prince, Stebbins, Sun, Vitale, …
• Accomplishments:
– Mutual understanding
– Kick-off of collaborations
– Exposure of the missions to people in the neighboring fields
Collaboration with Stanford
• UV LED discharge for DPF
• Other R&D for DECIGO
Summary
• DECIGO can detect GWs from the
inflation as well as can bring us
extremely interesting science.
• DPF has been selected as one of the
important mission candidates for small
science satellite series; they plan to
launch 3 missions in 5 years starting from
2011.
Let DPF fly!
Possible breakthrough for
3rd-generation detectors:
Displacement-noise free Interferometer
Kawamura and Chen, PRL, 93, (2004) 211103
Chen and Kawamura, PRL, 96 (2006) 231102
Motivation


Displacement noise: seismic Noise, thermal noise, radiation
pressure noise
Cancel displacement noise  shot noise limited sensitivity
Increase laser power  sensitivity improved indefinitely
Diplacement
noise
Displacement
noise
Cancel displacement noise
Shot noise
PD
Laser
Sensitivity

Increase laser power
Frequency
GW and mirror motion interact with
light differently
On
reflection
GW
On
propagation
Light
Mirror motion
Mirror motion
Difference outstanding for
GW wavelength  distance between masses
Cancel motion of objects
Clock
 BA   AB   BC   CB
 Motion of A, B, and C
cancelled
 GW signal remains
Why is it possible?
# of MQ (4) ＞ # of DOF (3)
MQ: Measurable quantity
DOF: Degree of freedom
Therefore a combination of MQs that is
free from DOFs exists!
Clock noise?
Clock
 BA   AB   BC   CB
 Motion: cancelled
 Clock noise:
not cancelled
Why?
# of DOF (Clock): 3
# of DOF (Displacement): 3
# of MQ: 4
Therefore it is not always possible to
make a combination of MQs that is free
from all the DOFs!
How can we cope with it?
d: # of dimensions, N: # of Objects
# of DOF (Displacement)：Nd
# of DOF (Clock) ：N
# of DOF (Total)：N(d+1)
# of MQ：N(N-1)
If N(N-1)>N(d+1) i.e. N>d+2
A combination of MQs that is free from
DOFs exists!
Displacement-noise free
interferometer
• Propagation time measurement 
interferometer
• Motion of object  displacement noise of
mirrors
• Clock noise  laser frequency noise
Example of DFI




Two 3-d bi-directional MZ
Take combination of 4
outputs
Mirror motion completely
cancelled
GW signal remains (f 2)
Experiment (Ideal)

One bi-directional MZ
Mirror motion
GW
Laser
PD
Extract
GW 
Mirror motion
Experiment (Practical)

EOM used for GW and mirror motion
Simulated mirror motion
Mirror motion GW
Laser
～
Simulated GW
～
Laser
PD
PD
Ideal
Practical
Results


Mirror motion cancels out
GW signal remains
Mirror motion to output
GW signal to output Difference
Difference
Mirror motion
GW signal
Sato, Kokeyama, Ward, Kawamura, Chen, Pai, Somiya, PRL 98 (2007) 141101
Possible breakthrough for
3rd-generation detectors:
Juggling Interferometer
Motivation
10-8
10-9
Displacement [mHz-1/2]
10-10
10-11
10-12
10-13
10-14
10-15
10-16
10-17
Seismic noise
Limiting the lowfrequency sensitivity
Pendulum thermal noise
Radiation pressure noise
10-18
10-19
10-20
Shot noise
1
10
Frequency [Hz]
100
• Lower frequency gives
higher GW signals.
• Suspension thermal
noise and seismic
noise are huge at low
frequencies.
• What if we can remove
suspension?
• Magnetic levitation is a
kind of suspension.
• Free-fall experiment is
just one shot.
km-class juggling interferometer
3 km
Beam
splitter
Laser
Fiber
Mirror
Laser beam
Clamp
Clamp
Simple Interferometer

Simple Michelson interferometer
– FP cavity is not necessary because the
sensitivity is limited by displacement noise at
low frequencies anyway

No fringe lock
– Fringe lock is not necessary because intensity
noise can be suppressed and no power recycling
is necessary
Data processing 1
Displacement

Produce displacement signal (x) from the
two PD outputs
Time
Noise caused by juggling
• x:
– Longitudinal position on release fluctuates
• dx/dt:
– Longitudinal velocity on release fluctuates
– Angular velocity on release fluctuates,
which couples with beam off-centering
• d2x/dt2:
– Above two effects couple with each other
• x, dx/dt, d2x/dt2 are constant in each
segment
Data processing 2
• In each segment, calculate <x>, <dx/dt>,
<d2x/dt2>
• Remove them from the data
Loss of GW signal
• A part of GW signal especially below 1
Hz is lost during the data processing 2.
• So is a part of any noise.
• S/N remains the same?
S/N degraded below 1 Hz
Displacement [mHz-1/2]
10-15
10-16
10-17
Shot noise after data processing
10-18
10-19
Original shot noise
10-20
0.1
1
Frequency [Hz]
10
Position
Continually
Freely falling
Hold
Release
Hold
Release
Hold
Time
Release
Clamp
~ 1 sec
Moving up and down
~2m
Juggling interferometer prototype