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. Ohmori, M. Kimura , Y. Saito, T. Suzuki F2f meeting, 2011/02/05

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.

(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

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

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

Specific weight of One-layer of MLI MLI Sample w [gf / m2] Crinkled type NRC-2 8.2 IHI Dimple : DAM-06 8.5 IHI Dimple : DAM-12 17.6 Kaneka :KFP-9B08 21 Kaneka :KF-9B / KN-20 26.9 Fermilab Tevatron :LHe Transfer Line DAM + Tissue Glass Paper 49.3 Fermilab Tevatron : Dipole magnet DAM + wavy DAM 67.3 Fermilab : SSC Candidate DAM(1 mil) +2-Cerex spunbonded nylon 55.8

Specifications of Candidate MLI : KFP-9B08 ( provided by Tochigi Kaneka Co., Ltd.) Type of MLI Double Aluminized Polyester Film Laminated with Separator Material All Polyester Thickness Specific weight Surface Resistance of Vapor Deposited Aluminum Layer : Rs less than 　　　for each side of DAM Thickness of Aluminum Layer *1 more than 50 nm for each side of DAM Normal Emissivity Less than 0.1 for non-laminated side Less than 0.6 for laminated side *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

(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

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

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.