ICRR Seminar 2009/07/24 Cryogenics in CLIO Masatake Ohashi and the LCGT collaboration.

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ICRR Seminar 2009/07/24

Cryogenics in CLIOMasatake Ohashi and the LCGT collaboration

CLIO is a cryogenic interferometer with 100m baseline in the Kamioka Mine.

CLIO is a prototype for LCGT.

CLIO objective is to demonstrate reduction of thermal noise by mirror cooling.

What is CLIO ?

Illustrated by Dr. Miyoki

Contents

• CLIO Outline– Sapphire Mirror– Cryogenic Suspension System– Cryostat and Cooling Technique

• Status of CLIO– Present Status as a prototype of

• Summary

Sapphire Mirror

CLIO Sapphire Mirror

Substrate: Crystal Systems (US)

Polish: CANON (Japan)

Coating: JAE (Japan) R=99.9%

Diameter 100mm Thickness 60mm (same as TAMA mirrors)

Sapphire Mirror- Absorption -

Absorption of laser light is important factor for mirror cooling.

We need better quality sapphire substrates.

LCGT requirement : substrate 20ppm/cm (not achieved) coating 1ppm (OK)

Sapphire Mirror- Mechanical Quality Factor -

Over 108 is obtained at low temperature.

Measured by Dr. Uchiyama

20K300K

Suspended by double sapphire wires

Sapphire Mirror- Dissipation of the Coating film -

Loss A

Temperature [K]Dissipation seems to be almost independent of Temperature

Measured by Dr. K. Yamamoto

Cryogenic Techniques

Cryogenic Technique- Estimated Heat Generation in the Mirror -

T=20 K

q=290 mW ・ Design Safety factor

Mirror substrate : SapphireSuspension rods : Sapphire

Exhaust heat

CLIO Cryostat for end mirror

58th Fujihara Seminar 2009/05/28

Low vibration Pulse Tube refrigerator

developed by KEK and SUMITOMO

8.8K45K

Cooling test and achieved temperature

Several days are necessary for mirror cooling.

Measured by Dr. Uchiyama

300K Radiation in vacuum pipes

Radiation shield (40K)Mirror (20K)

300K Radiation( straying )

300K Radiation from inside of vacuum pipes warms mirrors

Serious Problem for cooling

Radiation shield, Baffles, …

Radiation Shields (cloistered mirror)

Radiation shield for mirrors

Cryogenic suspension system

Mirror

Intermediatemass

Basic design is double pendulum

Cooling method by a cryocooler

58th Fujihara Seminar 2009/05/28

Cooling procedure

Cooling shortens length of suspension by 2mm STEP1

cooling mirror alignment

STEP4 cooling mirror alignment

Current status of CLIO

Noise budget at room temperature

Thermal noise of suspension

Thermal noise of mirror

Current sensitivity is limited by thermal noises

Expected Noise Spectrum at 20K

Frequency [Hz]100 1K10 10K

Shot Noise

Suspension Thermal Noise@300K

Mirror Thermal Noise@300K

Total@300K

Total@20K

This curve is already realized

We started mirror cooling last week.

Today’s DATA

Preliminary

One mirror is cooled to 14K.

• The Skewness characterizes the degree of asymmetry of a distribution around its mean.

Gaussian check : Skewness and kurtosis

Negatively skewed DistributionPositively skewed Distribution

Skewness :

• The Kurtosis measures the relative peakedness or flatness of distribution.

Kurtosis :

Skewness >0 Skewness < 0

• A distribution with positive Kurtosis is termed leptokurtic.

• A distribution with negative Kurtosis is termed platykurtic.

• A distribution with 0 Kurtosis is termed mesokurtic.

In the case of Gaussian, we expect that the values of Skewness and Kurtosis are 0.

Variance :

Gaussian check of CLIO DATA

CLIO Data Acquisition Lock Status

18:00 19:00 20:00 21:00 22:00 23:00 0:00 1:00

2009/4/30

JST Data Time

unlock

SUMMARY

Cryogenic prototype CLIO is

in commissioning phase.

Cryogenic interferometer is feasible. But we have to improve some points, especially, the combination of heat transfer and vibration isolation is important.

ＣＬＩＯの今後

• 低温ミラー性能のデモンストレーション

• 量子干渉計への改造（ Caltechとの共同研究）

• デジタル制御の導入（ＬＩＧ Oとの共同研究）

ICRR Seminar 2009/07/24 Cryogenics in CLIO Masatake Ohashi and the LCGT collaboration.

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