Status of LCGT and CLIO Masatake Ohashi (ICRR, The University of TOKYO) and LCGT, CLIO collaborators...

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


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.


LCGT on LIGO Web

Next generation IFO from Japan

TAUP 2007 Sendai Japan 2007/09/12

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.


Interferometer Design


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


Interferometer Design - Over View 2 -

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


Interferometer Design - Layout 1 -

Center room for IFO-1

Center room for IFO-2

3km arm

3km

arm

Two IFOs share the vacuum pipes


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)


Sapphire Mirror


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.


Sapphire Mirror- Mechanical Quality Factor -

Over 108 is obtained


Sapphire Mirror- Dissipation of the Coating film -

Loss A

ng

le

Temperature [K]

Dissipation is almost independent of Temperature


Sapphire Mirror- Thermal Expansion -

Thermal expansion is negligible at cryogenic temperature.

Th

erm

al Exp

an

sio

n

Temperature [K]


Cryogenic Techniques


Cryogenic Technique- Estimated Heat Generation in the Mirror -

T=20 K

q=290 mW ・ Design Safety factor

Mirror substrate : SapphireSuspension rods : Sapphire


Cooling method by a cryocooler


Seismic Noise Attenuation


Seismic Attenuation System (SAS)

• Inverted pendulum – 30mHz

• 3 cascaded GAS filter – 500mHz

• Test mass suspension– triple pendulum


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


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


CLIO


Cryogenic prototype for LCGT


Overview of CLIO


Cryostat for an end mirror


8.8K45K

63K

12.9K

Cooling test and achieved temperature


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.


Low vibration PT refrigeratorby KEK and SUMITOMO


Cryogenic suspension


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)


Radiation Shields


Cooling procedure

Cooling shortens suspension by 2mm

STEP1 cooling mirror alignment





Expected Noise Spectrum at 20K

Current best (300K)

Target sensitivity (300K)

Target sensitivity (20K)

Resonance of suspension system


Noise budget for CLIO (300K)

Cooling


YES !Thermal Noise of Aluminum Wires

Thermal noise reduced by cooling ?


CLIO Stability

Akutsu’s POSTER


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.


European Plan


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.

Status of LCGT and CLIO Masatake Ohashi (ICRR, The University of TOKYO) and LCGT, CLIO collaborators...

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Transcript of Status of LCGT and CLIO Masatake Ohashi (ICRR, The University of TOKYO) and LCGT, CLIO collaborators...