Transcript Cryogenic system design of LCGT

Cryogenic System design of LCGT
- Status of Cryogenic Design -
N. KIMURAA, S. KOIKEB, T. KUMEB, T. OHMORID,
Y. SAITOC, Y. SAKAKIBARAE, K. SASAKIA, Y. SATOC,
T. SUZUKIA, T. UCHIYAMAE, K. YAMAMOTOE,
H. YAMAOKAC, and LCGT Collaboration
A Cryogenics
Science Center/KEK
B
Mechanical Engineering Center/KEK
C
Accelerator Laboratory/KEK
D
Teikyo University
E
Institute for Cosmic Ray Research
University of Tokyo/ICRR
EGO-ICRR Meeting
Kashiwa, Japan, 4-5 October 2011 N. KIMURA
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Outline
Required Issues for the Cryogenics
Cryostat design
• Components
• Mechanical Analysis
• Thermal Analysis
• Performance of the proto-type cryocooler unit
• Estimation cooling characteristics of the
cryogenic load
Schedule
Future work
Summary
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Required Issues for the Cryogenics Design
• Temperature of the test mass/mirror < 20 K.
• Inner radiation shield have to be cooled < 8 K.
• The mirror have to be cooled without introducing
excess noise, especially vibration
from the cryo-coolers.
• Accessibility and enough space for
the installation work around the mirror
in the cryostat.
Estimated by Dr. Uchiyama (ICRR)
• Satisfy ultra high vacuum specification
< 10-7 Pa.
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Components of Mirror Cryostat
~3.8m
to SAS
Cryostat
Stainless steel t20mm
Diameter 2.4m
Height ~3.8m
M ~ 10 ton
Drawn by S. KOIKE (KEK)
Remote valve
Low vibration
cryocooler unit
Main beam
(1200mm FL)
Cryocoolers
Pulse tube, 60Hz
0.9 W at 4K (2nd)
36 W at 50K (1st)
Cryostat accompany with the four cryocooler units
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The interior of the cryostat
Drawn by S. KOIKE (KEK)
Support rods
View Ports
Heat path to
cryocooler
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Double radiation shields
with hinged doors
Static deformation analysis
S.KOIKE
Main vacuum duct and the duct to SAS are
not connected.
• periphery of the bottom : fix
•
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Modal analysis of outer shield
Mode frequency
Mass=
Remove support rod
Mode Frequency
Mass=
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S.KOIKE
Analyzing of Response to ground motion
resonant frequency
Cryo-top
Cryo-F
Cryo-L
Cryo-R
Y方向
X-direction
X方向
Input
Y-direction
Estimated Thermal Budget
Estimated Heat Loads at the radiation shields and Support posts
and rods
70
bythe
thetop
radiation
94 W
K at
of
at
the80
80K Kouter
outershield
shield
2.27.4
W Kbyatthe
theradiation
top of
at the
8 K8
inner
shield
K inner
shield
2.4 W by the radiation and
conduction
(support
posts and
Connection
point with
IM
tension rods) at 8 K
24 W by the radiation and
(support posts and
47 K atconduction
1st cold stage
tension rods) at 806.5
K K at 2nd cold
of Cryo-cooler
stage of Cryocooler
dT1st = 26 K
Very High PuritydT
Aluminum
2nd=0.5 K
Conductor (5N8)
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Low Vibration Cryo-cooler unit
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Estimated Heat load
1st Cold stage
Outer Shield
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◦
2nd Cold stage
(W)
Eleven View Ports
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Radiation From 300 K 70
Support post and Rods 24
Electrical wires
3 x 10-4
Total
W/unit
116
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•
Inner Shield
(W)
◦ Duct Shields*
< 0.05
(Beam and SAS)
◦ Eleven View Ports
0.4
◦ Radiation From 80 K
2.2
◦ Support post and Rods 2.4
◦ Electrical wires
3 x 10-4
◦ Mirror Deposition
0.9
◦ Scattering Light
?
Total
W/unit
5.9
1.5
*Heat Load of Duct Shields will be presented
by Mr. Sakakibara.
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Proto-type cryocooler unit under the performance test
Pulse tube type cryo-cooler
with anti-vibration stage
Vacuum duct for very high pure
aluminum thermal conductor
and radiation shield
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Tri-axial laser displacement meter
Vibration Level at edge of AL thermal conductor
Axial
Vertical
Horizontal
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PTC connection
L=2 m
F.F.T. analysis (Ex. Axial direction)
Results of displacement at connection point
Axial < 200 nm
Vertical < 50 nm
Horizontal < 10 nm
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Axial
Cooling curve of proto-type cryo-cooler unit
Reached
lowest temp.
2nd stage=4.8 K
1st stage=37 K
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Cooling Performance of Proto-type
Cryo-cooler Unit
Cooling Power per unit
4.5 W at 8 K
48 W at 75 K
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Estimation cooling characteristics
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Model is constructed to estimate initial cooling time
Y.SAKAKIBARA
Heat is transferred by conduction in sapphire fibers and heat links and radiation
Inner shield of 410 kg is connected to the 2nd stages of 4 cryocoolers
◦ Cooling power is derived from test result of proto-type cryo-cooler
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SuspensionKashiwa,
from isolation
system2011
is excluded
Japan, 4-5 October
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Effect on Diamond Like Carbon coating
Y.SAKAKIBARA
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Increased radiation by platform,
intermediate mass, and inside of inner
shield coated with DLC (Diamond Like
Carbon)
Absorptivity of DLC at 10 um is 0.41
(cf. emissivity of Cu and Al is 0.03)
◦ We assume that it equals emissivity
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Production plan of LCGT mirror cryostats
and peripheral components
2011 Jfy
‘11.3
2012 Jfy
‘12.3
‘13.3
We are here
Four Mirror Cryostats
Assemble and
factory test with
cryo-coolers
‘11.09.20&21
Contractors
were decided;
JEC- Tohrisya
Toshiba
Design by KEK
Proto-type
Cryo-cooler unit test
‘14.3
Manufacture components
Design by KEK
Cryo-cooler units
2013 Jfy
Production of
7 cryo-cooler
units
Custody at Kamioka
Performance test
Transport to Kamioka
Performance test
Duct shield units
Design by KEK
Transport to Kamioka
Production
of 9 cryocooler units
Production of Proto-type ducts
shield units with cryo-coolers
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Custody at Kamioka
Mirror Cryostats with the duct shields
Type-A (2-layer structure)
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Vacuum duct450
with radiation
shield
Mirror a cryostat
Gate valve
L=~17 m
Vacuum duct1000
with radiation
shield
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Upper tunnel containing pre-isolator
(short IP and top filter)
1.2m diameter 5m tall borehole
containing standard filter chain
Lower tunnel containing cryostat
and payload
Connection Port to SAS
L=~17 m
Vacuum duct1000
with radiation
shield
Gate valve
Status of the cryogenic payload for LCGT
• We have just started R&D and design
work for the cryogenic payload based
on the information from Roma.
• Key person of the LCGT cryogenic
payload group is Dr. K. Yamamoto.
• Mr. Koike, mechanical engineer in KEK,
is now calculating thermal analysis by
ANSYS.
• We are preparing a cryostat for the
cryogenic payload at ICRR.
• We would like to discuss it with INFN
group during the workshop.
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An example of a cryogenic payload’s drawing
drawing by S. KOIKE
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A cryogenic payload in the cryostat
drawing by S. KOIKE
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Summary
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The performance of the cryo-cooler unit with antivibration stage have almost confirmed, but need
some modification to clear the specification.
The design of the cryostat and cryo-cooler for LCGT
were almost finished.
The production of the components for the cryostat
have just started in this September 2011.
Performance of the first cryostat will be
demonstrated on the mid of 2012 Jfy.
Total performance of the first cryo-cooler will be
confirmed on the mid of this August.
To do works;
We have to fix the design of two kinds of duct shields
for beam duct and SAS connection.
 We also have to focus on R&D work for the cryogenic
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payload.
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Back UP
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MLI utilizes quite a lot of aluminized thin
polyester films as radiation shields.
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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.
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To reduce the total amount of out-gas,
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Thickness of polyester film must be
thin
Light Weight MLI
Total number of films in MLI must be
reduced
High Thermal Resistance
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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 m
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 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
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2010
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The measurement is now underway
MLI : Kaneka KFP-9B08
Back ground
(SUS Chamber)
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(2) High Thermal Resistance
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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 from
thermal resistance point of view.
⇒ Light weight MLI
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F.F.T. analysis (Vertical direction)
Vertical
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F.F.T. analysis (Horizontal direction)
Horizontal
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Appendix(Conduction cooling of
suspension system, No radiation)
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Thermal conductivity of heat links or sapphire fibers limits cooling time
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Appendix(Conduction and radiation cooling
of suspension system)
Radiation
Radiation dominates above 100 K
Conduction dominates below 100 K
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Incident Thermal Radiation through Duct
Shield
and
Cooling Time of Mirror
Yusuke SAKAKIBARA (ICRR)
2011.8.4 EGO-ICRR
LCGT f2fMeeting
meeting
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Incident Thermal Radiation through
Duct Shield
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Purpose of duct shield
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Thermal radiation from opening of 900 mm in diameter
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Cooling power 3.6 W at 4 K (4 pulse tube cry coolers of 0.9 W at 4 K)
Thermal radiation can be decreased if solid angle reduces
Thermal radiation reflected by metal shield pipe
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◦ Problem experienced in CLIO
Cryostat
Cryostat
Duct Shield
900 mm
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17 m
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Reducing thermal radiation by baffles
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Incident thermal radiation calculated using ray trace model by
counting up number of reflections
(Aluminum of A1070 measured at 10 um, 80 K)
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Calculation of incident thermal radiation
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Apertures of baffles change linearly
R=0.94 at 10 um
R=0.94±0.02
Worse case
R=0.96 P=0.172 W
Better case
R=0.92 P=0.0615 W
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Thermal radiation can be sufficiently
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reduced by baffles
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Cooling Time of Mirror
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Summary
• Thermal radiation through duct shield can be
sufficiently reduced by baffles
◦ 200 mW (100 mW x 2 duct shields)
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It takes 20 days to cool down mirror with DLC
coating
◦ Research for high emissivity coating is now
underway
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Calculation about incident heat through radiation
shields of LCGT ducts
ICRR，KEKA
Yusuke Sakakibara，Nobuhiro KimuraA，
Toshikazu SuzukiA，Kazuaki Kuroda，
Yoshio SaitoA，Shigeaki KoikeA，
Masatake Ohashi，Shinji Miyoki，
LCGT Collaboration
2011.9.18 JPS 2011 Autumn Meeting
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Contents
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S. KOIKE
Vibration Isolation System
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Schematic diagram
of cryostat
Beam Duct
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Background
◦ Cooling mirror to reduce thermal
radiation
◦ Cooling only cryostats
◦ Thermal radiation through holes
of cryostat is problematic
Calculating incident thermal
radiation from ducts
◦ Comparison with experimental
value
Calculation in LCGT case
Laser Beam
Mirror(20 K)
Inner Shield(8 K) Outer Shield(80 K)
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Purpose of duct shield
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Thermal radiation from opening of 900 mm in diameter
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Cooling power 3.6 W at 4 K (4 pulse tube cry-coolers of 0.9 W at 4 K)
It is necessary to reduce thermal radiation
Thermal radiation appears to be proportional to solid angle to hole
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Solid Angle
Cryostat
Cryostat
Duct Shield
29.2 W
900 mm
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17 m
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Cooling test in LCGT prototype
（CLIO）
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Thermal radiation reflected by duct shield
◦ Experimentally verified
T. Tomaru et al. Jpn. J. Appl. Phys. 47 (2008) 1771-1774
Incident power
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Calculated by tracing rays (reflectivity is 0.94)
600 times larger than considered from solid angle
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Solid Angle
Cryostat
Cryostat
Duct Shield
29.2 W
900 mm
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17 m
6.22 W
Although "black"
duct shield
absorbs thermal
radiation, it
radiates itself.
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Reducing thermal radiation by baffles
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Reflecting thermal radiation to room temperature side by baffles
Increasing number of reflections of rays by baffles
Room Temperature
Low Temperature
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Calculation of incident thermal radiation
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It is necessary to reduce incident heat by optimizing layout and shape of
baffles
Incident thermal radiation calculated using ray trace model by counting up
number of reflections
:Area of baffle aperture
:Number of reflections
:Reflectivity of duct
Subscript d means duct, r room temperature side of
baffles , c cryogenic temperature side of baffles
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Comparison with experimental value
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Experiment in prototype of cryogenic interferometer(CLIK)
◦ Tomaru T et al. J. Phys.: Conf. Ser. 122 (2008) 012009
◦ Introducing 2 baffles, reflectivity of duct and baffles is 0.95
◦ Incident heat 7.9 mW
Calculated value 18.6 mW
Calculated value is consistent with experimental value within several
times
◦ If reflectivity is 0.90, calculated value is exactly experimental value
◦ Change of several percent of reflectivity leads to several times’
difference
of incident heat because
3 cm
117 cm of many reflections.
Room Temperature
7 cm
Cryogenic Temperature
Baffle
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2.3 cm
135 cm
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Calculation in LCGT case
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Apertures of baffles change linearly
R=0.94 at 10 μm (reflectivity of duct and baffles)
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R=0.94±0.02
(measured value of
aluminum A1070 at
wavelength 10 μm, 80 K)
Worse case
R=0.96 P=0.283 W
Better case
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R=0.92 P=0.100 W
High absorptivity coating （DLC）
Room Temperature Cryogenic Temperature
DLC coating
Position of baffles x=0,10,14,16,17 m
Without DLC 0.163 W
With DLC 0.0883 W
Heat absorbed by baffles
Heat load becomes smaller
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Baffles whose room temperature sides are coated with DLC (DiamondLike-Carbon)
Baffles whose cryogenic temperature sides are NOT coated with DLC
because it radiates
• Reflectivity of Aluminum A1070 CP+DLC(1.0 μm in thickness) at
wavelength 10 μm, 80 K is measured; 0.59
◦ Reflectivity of duct 0.94
◦ Reflectivity of room temperature sides of baffles 0.59
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◦ Reflectivity
of cryogenic temperature sides of baffles 0.94
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Budget of thermal loads on 2nd stages
of LCGT cryocoolers
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Heat sources
◦ Radiation through duct shields
◦ Eleven view ports
◦ Radiation from outer shield
◦ Conduction from supports
◦ Absorption of laser by mirror
W
0.3
0.4
2.2
2.4
0.9
◦ Scattering of laser by mirror
Total
N. KIMURA
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～9
Thermal radiation through duct shields
can be sufficiently reduced by baffles
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S. KOIKE
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
Summary
◦ We calculated incident thermal radiation through duct
shield
◦ Calculated value is consistent with experimental value
◦ Thermal radiation can be sufficiently reduced by baffles
◦ Baffles coated with high absorptivity coating were useful

Future works
◦ We will calculate detail to design LCGT duct shields
◦ We will verify calculation result using LCGT cryostat
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Appendix (Heat capacity)
Sapphire: Y.S.Touloukian: "Thermophysical Properties of Matter Volume 5 Specific Heat Nonmetallic Solids," IFI/Plenum (1970)
Copper:EGO-ICRR
AIST Network
Database System for Thermophysical Property Data
Meeting
Aluminum:
NIST http://cryogenics.nist.gov/MPropsMAY/5083%20Aluminum/5083Aluminum_rev.htm
Kashiwa,
Japan, 4-5 October 2011 N. KIMURA
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Appendix (Thermal conductivity)
Sapphire: Y.S.Touloukian: "Thermophysical Properties of Matter Volume 5 Specific Heat Nonmetallic Solids," IFI/Plenum (1970)
EGO-ICRR
Meeting
Aluminum:
AIST Network
Database System for Thermophysical Property Data
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Appendix (Emissivity)
Sapphire: Y.S.Touloukian: "Thermophysical Properties of Matter Volume 5 Specific Heat Nonmetallic Solids," IFI/Plenum (1970)
Copper:EGO-ICRR
Y.Sakakibara Meeting
et al. TEION KOGAKU 2011;46
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