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.