Status of LCGT and CLIO Masatake Ohashi (ICRR, The University of TOKYO) and LCGT, CLIO collaborators TAUP2007 Sendai, Japan 2007/9/12.

Status of LCGT and CLIO

Masatake Ohashi(ICRR, The University of TOKYO)

andLCGT, CLIO collaborators

TAUP2007Sendai, Japan

2007/9/12

Status of LCGT and CLIO

Masatake Ohashi(ICRR, The University of TOKYO)

andLCGT, CLIO collaborators

TAUP2007Sendai, Japan

2007/9/12

TAUP 2007 Sendai Japan 2007/09/12TAUP 2007 Sendai Japan 2007/09/12

Contents

• LCGT Outline• Status of LCGT

– Interferometer Design– Sapphire Mirror and its Suspension– Cryostat and Cooling Technique

• Status of CLIO– Present Status as a proto-type of

LCGT

• Summary

TAUP 2007 Sendai Japan 2007/09/12illustration: KAGAYA

Large-scale Cryogenic Gravitational wave Telescope （ LCGT） 180Mpc

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LCGT Outline

• It is 3km Fabry-Perot interferometer with power recycling and broadband RSE.

• Main mirrors made of sapphire are cooled at 20K.

• It is built at underground site in Kamioka Mine.

• Two independent interferometers are installed.

• The main target is the coalescence of Binary Neutron Star ｓ at 180Mpc.

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LCGT on LIGO Web

Next generation IFO from Japan

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Merit of Underground site

Quiet !

Seismic activity of city area

Seismic activity of Kamioka Mine

The point is that

at least 100m below land surface is necessary to prevent wind effect.

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Interferometer Design

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Interferometer Design - Over View 1 -

• Detector parametersLaserNd:YAG laser (1064nm)Injection lock + MOPA

Power : 150 W

Main InterferometerBroad band RSE configuration

Baseline length : 3kmBeam Radius : 3-5cmArm cavity Finesse : 1550Power Recycling Gain : 11Signal Band Gain : 15Stored Power : 771kWSignal band : 230Hz

Vacuum systemBeam duct diameter : 100cmPressure : 10-9 Torr

MirrorSapphire substrate + mirror coating

Diameter :25cmThickness :15cmMass : 30 kgAbsorption Loss : 20ppm/cmTemperature : 20 KQ = 108

Loss of coating : 10-4

Final SuspensionSuspension + heat link with 4 Sapphire fibersSuspension length :40cmFiber diameter :1.5mmTemperature : 16KQ of final suspension : 108

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Interferometer Design - Over View 2 -

Main IFO : 3km IFO Input optics : Two MCs, Modulators, MMTOutput optics: OMC, Photo detectors

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Interferometer Design - Layout 1 -

Center room for IFO-1

Center room for IFO-2

3km arm

3km

arm

Two IFOs share the vacuum pipes

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Interferometer Design- RSE -

• Merit of RSEHigh-finesse cavity and moderate PRGEasier to realize high power in cavitiesSmaller transmission light in opticsFlexible optimization for GW sources

Independent adjustment of power in cavities and signal bandNarrow-band observation (optional)

Main reason for LCGT

Absorption in sapphire substrates Heat absorption : 20ppm/cm x 15 cm = 300 ppm Cooling power : 1W for each mirror

Laser power on BS should be less than ~1kW (safety factor 3)

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Sapphire Mirror

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Sapphire Mirror- Absorption -

Laser light absorption is important factor for cooling.

LCGT requirement :

substrate 20ppm/cm (-> 250mW) coating 1ppm (-> 40mW)

We need high quality sapphire substrate.

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Sapphire Mirror- Mechanical Quality Factor -

Over 108 is obtained

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Sapphire Mirror- Dissipation of the Coating film -

Loss A

ng

le

Temperature [K]

Dissipation is almost independent of Temperature

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Sapphire Mirror- Thermal Expansion -

Thermal expansion is negligible at cryogenic temperature.

Th

erm

al Exp

an

sio

n

Temperature [K]

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Cryogenic Techniques

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Cryogenic Technique- Estimated Heat Generation in the Mirror -

T=20 K

q=290 mW ・ Design Safety factor

Mirror substrate : SapphireSuspension rods : Sapphire

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Cooling method by a cryocooler

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Seismic Noise Attenuation

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Seismic Attenuation System (SAS)

• Inverted pendulum – 30mHz

• 3 cascaded GAS filter – 500mHz

• Test mass suspension– triple pendulum

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Suspension Point Interferometer (SPI)- Background and Purpose -

(i) Seismic noisethrough heat link wires(HLWs)

DampingMagnets

VibrationIsolationSystem(Room temp.)

CryogenicSuspension(4K-20K)Upper Mass(SPI)

Test Mass (Main IFO)

Recoil MassCoil-magnetActuators

Upper RecoilMass

Flex Joint

GAS filter

Displacement sensorCoil-magnet actuator

Acc. sensor

InvertedPendulum

SuspensionPlatform

77K shield4.2K shield

(ii) Magnet - CoilActuator Noise

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Schedule and Budget

LCGT proposal is submitted to the Ministry of Education and Science （ MEXT) as one of recommended projects of the University of TOKYO. But LCGT will not start at 2008.

130 M$ without salary and maintenance

We will retry next year.

2008 2009 2010 2011 2012 2013 2014

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CLIO

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Cryogenic prototype for LCGT

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Overview of CLIO

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Cryostat for an end mirror

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8.8K45K

63K

12.9K

Cooling test and achieved temperature

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Cooling summary

Cooling time

Mirror tempHeat in the suspension

Heat at the 1st cooling2006/02

Inline end 176hourstart 07/06/22,10:00

13.5K 40mW N/A

Inline near 174hourstart 07/06/22,10:00

13.4K 36mW N/A

Per arm end

164hourstart 07/04/27,11:05

12.5K 62mW#1 116mW

Per arm near

193hourstart 07/08/16,12:30

13.8K 29mW 109mW

#1; No shield for radiation from the outer shield at 63K.

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Low vibration PT refrigeratorby KEK and SUMITOMO

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Cryogenic suspension

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Heat Transfer

Radiation shield (40K)Mirror (20K)

300K Radiation( straying )

300K Radiation from window of Gate Valve warms mirrors

Serious Problem for cooling

Good Heat Transfer, Baffles, …

Gate Valve (300K)

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Radiation Shields

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Cooling procedure

Cooling shortens suspension by 2mm

STEP1 cooling mirror alignment

STEP4 cooling mirror alignment

STEP2 cooling mirror alignment

STEP3 cooling mirror alignment

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Expected Noise Spectrum at 20K

Current best (300K)

Target sensitivity (300K)

Target sensitivity (20K)

Resonance of suspension system

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Noise budget for CLIO (300K)

Cooling

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YES !Thermal Noise of Aluminum Wires

Thermal noise reduced by cooling ?

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CLIO Stability

Akutsu’s POSTER

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SUMMARY

• We will submit LCGT budget request for FY2009 again next year.

• Cryogenic prototype CLIO was completed. Now in commissioning phase.

• We demonstrated to operate interferometer with cryogenic mirrors, but careful heat transfer is necessary for cooling.

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European Plan

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Interferometer Design - Layout 2 -

Baffle for LCGTSpecification of LCGT

Tube diameter 1000mmMirror diameter 250mmMirror distance 600mmMirror offset 340mmSeismic motion 1 x 10-11m/Hz1/2@30Hz

Estimated scattered light noise4.2 x 10-21m/Hz1/2@30Hz (Safety factor=7)

1/10

45

(for one mirror)

Integration

Each reflection

Baffle designNumber: 45x2for one armHeight: 35~50mmSurface: DLC coatings

Diamond-Like Carbon (DLC) coatingsSurface roughness: Ra=20nmOutgassing: lower than SS316 with baking

Reflectivity: 5% for p-polarization at 45deg.