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

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 ?

ICRR Seminar 2009/07/24

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

LCGT

• Summary

ICRR Seminar 2009/07/24

Sapphire Mirror

ICRR Seminar 2009/07/24

CLIO Sapphire Mirror

Substrate: Crystal Systems (US)

Polish: CANON (Japan)

Coating: JAE (Japan) R=99.9%

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

ICRR Seminar 2009/07/24

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)

ICRR Seminar 2009/07/24

Sapphire Mirror- Mechanical Quality Factor -

Over 108 is obtained at low temperature.

Measured by Dr. Uchiyama

20K300K

Suspended by double sapphire wires

ICRR Seminar 2009/07/24

Sapphire Mirror- Dissipation of the Coating film -

Loss A

ng

le

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

Measured by Dr. K. Yamamoto

ICRR Seminar 2009/07/24

Cryogenic Techniques

ICRR Seminar 2009/07/24

Cryogenic Technique- Estimated Heat Generation in the Mirror -

T=20 K

q=290 mW ・ Design Safety factor

Mirror substrate : SapphireSuspension rods : Sapphire

Exhaust heat

ICRR Seminar 2009/07/24

CLIO Cryostat for end mirror

ICRR Seminar 2009/07/24

58th Fujihara Seminar 2009/05/28

Low vibration Pulse Tube refrigerator

developed by KEK and SUMITOMO

8.8K45K

63K

12.9K

Cooling test and achieved temperature

Several days are necessary for mirror cooling.

Measured by Dr. Uchiyama

ICRR Seminar 2009/07/24

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, …

ICRR Seminar 2009/07/24

Radiation Shields (cloistered mirror)

Radiation shield for mirrors

ICRR Seminar 2009/07/24

Cryogenic suspension system

Mirror

Intermediatemass

Basic design is double pendulum

ICRR Seminar 2009/07/24

Cooling method by a cryocooler

ICRR Seminar 2009/07/24

58th Fujihara Seminar 2009/05/28

Cooling procedure

Cooling shortens length of suspension by 2mm STEP1

cooling mirror alignment

STEP4 cooling mirror alignment

STEP2 cooling mirror alignment

STEP3 cooling mirror alignment

Current status of CLIO

ICRR Seminar 2009/07/24

Noise budget at room temperature

Thermal noise of suspension

Thermal noise of mirror

Current sensitivity is limited by thermal noises

ICRR Seminar 2009/07/24

Expected Noise Spectrum at 20K

Frequency [Hz]100 1K10 10K

10-21

10-20

10-19

10-18

10-17

10-16

Shot Noise

Suspension Thermal Noise@300K

Mirror Thermal Noise@300K

SQL

Total@300K

Total@20K

This curve is already realized

We started mirror cooling last week.

ICRR Seminar 2009/07/24

Today’s DATA

Preliminary

One mirror is cooled to 14K.

ICRR Seminar 2009/07/24

• 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

lck

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.

ICRR Seminar 2009/07/24

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