Transcript Requirements for Multi-layer Insulation 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.
• 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
MLI Sample
TMP
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
35  5 mm
Specific weight
21 1 gf / m2
Surface Resistance of Vapor Deposited
Aluminum Layer : Rs
less than 1  for each side of DAM
Thickness of Aluminum Layer *1
more than 50 nm for each side of DAM
Normal Hemispherical 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
Warm Drum (～80K)
Cold Drum (～5K)
GM Refrigerator
MLI
( 1.5 W at 4K )
Heat Leak Meter
Test calorimeter
Calibration Hearter
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.