LCGT計画について

大型低温重力波望遠鏡の開発・設計（V）
共同利用研究発表会
2003.12.19@ICRR
東大宇宙線研
黒田和明，大橋正健，三代木伸二，内山隆、石塚秀喜，山元一広，早河秀章、
岡田淳、近藤寿浩、奥富聡、笠原邦彦、徳成正雄、阿久津朋美
国立天文台
藤本眞克，川村静児，高橋竜太郎，山崎利孝，新井宏二，辰巳大輔、上田暁俊，
福嶋美津広，佐藤修一，常定芳基，朱宗宏
高エ研
新冨孝和，山本明，鈴木敏一，斎藤芳男，春山富義，佐藤伸明，東保男，
都丸隆行
東大理
坪野公夫，安東正樹，沼田健司，麻生洋一
電通大レーザー研
植田憲一，米田仁紀，中川賢一，武者満
東大新領域
三尾典克，森脇成典，宗宮健太郎，竹野耕平、丹治亮
東大地震研
新谷昌人，高森昭光
大阪市立大、神田展行，産総研、寺田聡一，通総研、長野重夫，阪大理、田越秀行，
京大理、中村卓史，京大基研、佐々木節，田中貴浩，
新潟大理、大原謙一，高橋弘毅，早大理工、前田恵一、関戸文、
お茶大、阪田紫帆里、川添史子、
California Insititue of Technology、宮川治， The University of Western Australia、
M.E. Tobar
ＬＣＧＴの目的
• Einsteinの一般相対性理論により予言され、
Taylor & Hulseにより間接的に確認された重
力波を直接に検出することにより、重力理論
の検証を行う
• 天体からの重力波を頻度高く捉えることによ
り重力波天文学を開始する
Sources of Gravitational Wave (GW)
• Coalescence of binary
neutron stars
• Supernova explosion
• Coalescence of binary
black holes
• Falling stars into black
holes
• Spinning neutron star
• Orbiting binary stars
• Cosmological background
• Vibration of a cosmic
string
２重中性子星系と予想される頻度
•
•
•
•
PSR B1534+12 (0.5kpc) 10-6 in Galaxy
PSR B1913+16 (7.3kpc) 10-7 in Galaxy
PSR B2127+11C (10.6kpc) in M15
PSR J0737+3039 (0.5-0.6kpc) ~10-5 in Galaxy
When GW passes through space where two masses
are placed, a distance between them changes.
• Suspended mirror (Mx)
and suspended beam
splitter (BS) behave as
test masses for GW
• Michelson Interferometer
measures differential
displacement between
two arms in optical phase
• Typical magnitude of the
event at Virgo cluster is
10-14 rad, 10-18 m for 1km
baseline
• To increase phase
sensitivity, optical path is
folded many times using
Delay-Line, Fabry-Perot,
and so on
Several projects on the Earth are ongoing
TAMA
The Objective of TAMA is to develop
advanced technologies for km scale
interferometer and to observe possible
ＧＷ events in our Galaxy.
The funding originally covered five
years.
We began its construction in April of
1995.It ends in this March after two
years extension. Four year research
money has been approved from this
April.
TAMAによる観測
LIGO-GEO-TAMAの共同観測を2002年８月に実施し（TAMAは25時間
分記録），2003年２月１４日から再び共同観測を行っており，４月６日に
1000時間を超えた．４月１４日に終了する予定である．各検出器の到達感
度と稼動率は表の通りである．
到達距離
kpc
最長ロック
時間 hr
稼動率
%
３５
２０．５
８１
Hanford
4km
３００
６６．２
６８
Hanford
2km
２００
１２．４
５３
Livingston
８００
６．５
３８
TAMA
GEO
備
考
１９%
調整中
Since BNS exist and the signal
of the coalescence is precisely
predicted, the event is the most
important target of the ground
based interferometric detectors.
However, since the event rate is
10-6 per year per matured galaxy
as ours, we have to wait more
than 30 years on average by the
sensitivity to observe the VIRGO
cluster（20Mpc). Because there
is less than one galaxy per cubic
Mpc.
Therefore, it is clear to everyone
to develop more sensitive
detector to see more remote
galaxies. Expected rate is 0.050.6 events/year for 244Mpc of
the LCGT target sensitivity.
低温干渉計LCGT計画, R&D
Revised LCGT のR&D
CLIO100の建設・観測
TAMA感度向上＆観測
重力波データ解析向上
Characteristic of LCGT
• Cryogenics
– 20K sapphire mirror
• Underground
– Stable & hard rock
• Parallel Interferometers
– Coincidence Observation
Cooling test
R&Ds for Cryogenic mirror
Contamination test
Mechanical Q test
Another example of the measured heat conductivity of sapphire fibers.
The sharp peak is believed to be a manifestation of goodness of the crystal.
This measurement proved the dependence of the fiber heat conductivity
On its diameter. Capacity varies with the third power of its diameter.
The next step of R&D for LCGT is to establish a
cryogenic interferometer. Suspension prototype was
tested in Kashiwa campus in ICRR.
Fake elimination using parallel Interferometers
• Assumption of the TAMA fake event << 1 / 1hour
• Coincidence analysis of two identical interferometer
placed side by side
• Probability detecting noise within ±Δt is p^2 Δt
• Δt～0.5ms×3
• Expected rate of the signal event is assumed as
1event/year ->3×10^{-8} /s
• p^2 Δt < 0.27% ×｛3×10^{-8}}= 8×10^{-11} / s =
2.7×10^{-3} / year
• p< 2.3×10^{-4} = 1 / (1.2 hour)
An Optical Design of LCGT interferometer
Optical Design Parameters
•
Main Interferometer
– Resonant Sideband Extraction
with power recycling, broad band configuration
– Arm cavity length
3000 m
– Power in arm cavities
800 kW
– Signal bandwidth
200 Hz
– Arm cavity finesse
1250
– Power recycling gain
10
– Signal band gain
10
・ Input optics
－Power transmittance
－Modulation sidebands
1st Mode cleaner
2nd Mode cleaner
・Laser source
- Output power 300W
- Wavelength 1064nm
33.3%
15 MHz, 50 MHz
10m Triangle ring cavity, 4.5kHz, FSR 15 MHz
180m Triangle ring cavity, 350Hz, FSR833kHz
・ Core optics
－Main Mirror: sapphire, 20K, 30cm, 18cm, 50kg
－Substrate optical loss 500ppm/18cm; heat absorption 20ppm/cm
・ PRM, SEM, BS, MC mirrors: Fused silica
Design detail
•
•
•
•
•
•
•
Suspension point interferometer
Vacuum system
Suspension system
Refrigerator system
Heat link system
Data acquisition system
Others
• Pressure
– 2X10-7 Pa
• Ducts
Vacuum System
–
–
–
–
Total length 3km
1.2m Diameter
11m Unit
Titanium or Stainless steel
• Pumps
– 10 Root pumps
– 30 Turbo molecular pumps or 10 Cryopumps
– 30 Ion pumps
• Optical Buffles
–
–
–
–
10cm Height
Made by M2052
DLC (diamond likecarbon)
80 pieces
Test mass of LCGT is connected to a cooling system by a heat link that introduces
mechanical noise. A suspension point interferometer is introduced to maintain high
attenuation of seismic and mechanical noise without degrading high heat
conductivity.
Schematic diagram of the installation of a main mirror with a mirror
of SPI. Outside of the cryogenic region, a super attenuator of vibration
is mounted inside a common vacuum. Heat budget is calculated according
to an experiment using a practical system (KLIC)
LCGT Schedule
Tunnel
Vaccu
m
Optics
Electric
Data
1st
year
*******
**
2nd
year
*******
3rd year 4th year 5th year
*******
*******
install
**
**
*******
install
*******
***
*****fin
***
Estimated budget (to be revised)
• Tunnel Construction
• Vacuum system
• Cryogenics
• Optics
• Suspension system
• Laser system
• Control system
• Computer
• Others
Total
3400
12100
400
800
260
400
100
200
340
18000
M JpnYen
まとめ
• 新しい設計に基づく詳細設計
• CLIOによる実践的干渉計技術の確立
• TAMAの結果
– 目標感度までもう一息の感度達成
– 市街地においても世界最高の連続観測実績を達成
• 経費の見積もりを継続中

Download Report