1. 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

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. 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

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

6. 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

7. 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

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. 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

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.