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Requirements for Multi-layer Insulation (MLI) in the LCGT Cryostat

Requirements for Multi-layer Insulation (MLI) in the LCGT Cryostat. (1) Low out-gas rate from the MLI (2) Low heat leak through the MLI. T. Ohmoti, M. Kimura , Y. Saito, T. Suzuki F2f meeting, 2011/02/05. MLI utilizes quite a lot of aluminized thin polyester films as radiation shields.

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Requirements for Multi-layer Insulation (MLI) in the LCGT Cryostat

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  1. Requirements forMulti-layer Insulation (MLI) in the LCGT Cryostat (1) Low out-gas rate from the MLI (2) Low heat leak through the MLI T. Ohmoti, M. Kimura , Y. Saito, T. Suzuki F2f meeting, 2011/02/05

  2. MLI utilizes quite a lot of aluminized thin polyester films as radiation shields. • The polyester film exhausts water vapor, which may dim the optical system of the Laser-Interferometer. • The exhaust rate of the water vapor may be reduced much at cryogenic temperature. But it is important to know the general characteristics of out-gas rate at room temperature.

  3. (1) To reduce the total amount of out-gas, • Thickness of polyester film must be thin Light Weight MLI • Total number of films in MLI must be reduced High Thermal Resistance

  4. Test chamber MLI Sample TMP Measurement of Out-gas Rate from the Light Weight MLI Test Apparatus MLI Sample : Kaneka KFP-9B08 Aluminized 9mm polyester film laminated with thin polyester paper

  5. The measurement is now underway. MLI : Kaneka KFP-9B08 Back ground (SUS Chamber)

  6. Specific weight of One-layer of MLI

  7. Specifications of Candidate MLI : KFP-9B08 ( provided by Tochigi Kaneka Co., Ltd.) *1 : estimated by the aluminum thickness data obtained by the atomic absorption spectroscopy reported by Teikyo University in the International Conference of Cryogenic Engineering, 2010

  8. (2) High Thermal Resistance • Heat transfer mechanisms in MLI qt = qr + qc Radiation term qr and Conduction term qc are comparable at good fabrication condition. Conduction term is governed by contact pressure between reflective films at the self-compression state. Radiation term is governed by total number of films. Thin polyester film will reduce the contact pressure. ⇒Light weight MLI

  9. MLI Sample Warm Drum (～80K) Cold Drum (～5K) GM Refrigerator ( 1.5 W at 4K ) MLI Heat Leak Meter Calibration Hearter Measurement of Heat Flux through MLI Test calorimeter

  10. Important Test Condition • Thermal performance of MLI fabricated in the LCGT cryostat must be evaluated by the data obtained in the laboratory. • Key test condition is the compressive pressure between adjacent layers of MLI. • Compressive pressure can be evaluated by the layer density of MLI • The layer density of MLI in LCGT cryostat must estimated. • The actual key test condition of MLI in the laboratory is the layer density of MLI.

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