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

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 Apparatus

Test chamber

TMP

MLI Sample

MLI Sample : Kaneka KFP-9B08 Aluminized 9m polyester film laminated with thin polyester paper

Back ground(SUS Chamber)

The measurement is now underway.

MLI : Kaneka KFP-9B08

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 LineDAM + Tissue Glass Paper 49.3

Fermilab Tevatron : Dipole magnetDAM + wavy DAM 67.3

Fermilab : SSC CandidateDAM(1 mil) +2-Cerex spunbonded nylon 55.8

Specifications of Candidate MLI : KFP-9B08

m535

2m/gf121

1

( provided by Tochigi Kaneka Co., Ltd.)

Type of MLIDouble 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 Hemispherical EmissivityLess 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

Test calorimeter

MLI Sample

GM Refrigerator

( 1.5 W at 4K )

Cold Drum (～5K)

Calibration HearterHeat Leak Meter

Warm Drum (～ 80K)

MLI

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.