icrr seminar 2009/07/24 cryogenics in clio masatake ohashi and the lcgt collaboration
TRANSCRIPT
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