ICRR Seminar 2009/07/24 Cryogenics in CLIO Masatake 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 10 8 is obtained at low temperature. Measured by Dr. Uchiyama 20K 300K Suspended by double sapphire wires ICRR Seminar 2009/07/24

Sapphire Mirror - Dissipation of the Coating film - Loss Angle 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 : Sapphire Suspension rods : Sapphire Exhaust heat ICRR Seminar 2009/07/24

CLIO Cryostat for end mirror ICRR Seminar 2009/07/24

58 th Fujihara Seminar 2009/05/28 Low vibration Pulse Tube refrigerator developed by KEK and SUMITOMO

8.8K 45K 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 Intermediate mass Basic design is double pendulum ICRR Seminar 2009/07/24

Cooling method by a cryocooler ICRR Seminar 2009/07/24

58 th 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 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 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