cryogenics in clio masatake ohashi and the lcgt collaboration
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58th Fujihara Seminar 2009/05/28
Cryogenics in CLIOMasatake Ohashi and the LCGT collaboration
58th Fujihara Seminar 2009/05/28
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
58th Fujihara Seminar 2009/05/28
Contents
• CLIO Outline– Sapphire Mirror– Cryogenic Suspension System– Cryostat and Cooling Technique
• Status of CLIO– Present Status as a prototype of
LCGT
• Summary
58th Fujihara Seminar 2009/05/28
Sapphire Mirror
58th Fujihara Seminar 2009/05/28
CLIO Sapphire Mirror
Substrate: Crystal Systems (US)
Polish: CANON (Japan)
Coating: JAE (Japan) R=99.9%
Diameter 100mm Thickness 60mm (same as TAMA mirrors)
58th Fujihara Seminar 2009/05/28
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)
58th Fujihara Seminar 2009/05/28
Sapphire Mirror- Mechanical Quality Factor -
Over 108 is obtained at low temperature.
Measured by Dr. Uchiyama
20K300K
Suspended by double sapphire wires
58th Fujihara Seminar 2009/05/28
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
58th Fujihara Seminar 2009/05/28
Cryogenic Techniques
58th Fujihara Seminar 2009/05/28
Cryogenic Technique- Estimated Heat Generation in the Mirror -
T=20 K
q=290 mW ・ Design Safety factor
Mirror substrate : SapphireSuspension rods : Sapphire
Exhaust heat
58th Fujihara Seminar 2009/05/28
CLIO Cryostat for end mirror
58th Fujihara Seminar 2009/05/28
Low vibration Pulse Tube refrigerator
developed by KEK and SUMITOMO
58th Fujihara Seminar 2009/05/28
8.8K45K
63K
12.9K
Cooling test and achieved temperature
Several days are necessary for mirror cooling.
Measured by Dr. Uchiyama
58th Fujihara Seminar 2009/05/28
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, …
58th Fujihara Seminar 2009/05/28
Radiation Shields (cloistered mirror)
Radiation shield for mirrors
58th Fujihara Seminar 2009/05/28
Cryogenic suspension system
Mirror
Intermediatemass
Basic design is double pendulum
58th Fujihara Seminar 2009/05/28
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
STEP2 cooling mirror alignment
STEP3 cooling mirror alignment
58th Fujihara Seminar 2009/05/28
Current status of CLIO
Noise budget at room temperature
58th Fujihara Seminar 2009/05/28
Thermal noise of suspension
Thermal noise of mirror
Current sensitivity is limited by thermal noises
58th Fujihara Seminar 2009/05/28
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.
Today’s DATA
58th Fujihara Seminar 2009/05/28
Preliminary
One mirror is cooled to 14K.
58th Fujihara Seminar 2009/05/28
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.
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