Cryogenic System design of LCGT - Status of Cryogenic Design -

EGO-ICRR MeetingKashiwa, Japan, 4-5 October 2011 N. KIMURA

Cryogenic System design of Cryogenic System design of LCGTLCGT

- Status of Cryogenic Design -- 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/KEKB Mechanical Engineering Center/KEKC Accelerator Laboratory/KEKD Teikyo UniversityE Institute for Cosmic Ray Research

University of Tokyo/ICRR


2

Outline Required Issues for the Cryogenics Cryostat design

• Components• Mechanical Analysis• Thermal Analysis• Performance of the proto-type cryo-

cooler unit• Estimation cooling characteristics of

the cryogenic load Schedule Future work Summary


• 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.

• Satisfy ultra high vacuum specification

< 10-7 Pa.

Required Issues for the Cryogenics Design

Estimated by Dr. Uchiyama (ICRR)


Main beam(1200mm FL)

to SAS

View ports

Remote valve

Low vibration cryocooler unit

Main LASER beam

2.4m

~3

.8m

CryostatStainless steel t20mmDiameter 2.4mHeight ~3.8mM ~ 10 ton

CryocoolersPulse tube, 60Hz0.9 W at 4K (2nd)36 W at 50K (1st)

Drawn by S. KOIKE (KEK)

Cryostat accompany with the four cryocooler Cryostat accompany with the four cryocooler unitsunits

Components of Mirror Cryostat


The interior of the cryostat The interior of the cryostat

Double radiation shields with hinged doors

Support rods

View Ports

Heat path to cryocooler

Drawn by S. KOIKE (KEK)


Static deformation analysisStatic deformation analysis

• Main vacuum duct and the duct to SAS are not connected.• periphery of the bottom : fix

S.KOIKE


Modal analysis of outer shieldModal analysis of outer shield

Mass=

Mode frequency

Mass=

S.KOIKE

Remove support rodMode Frequency

Cryo-top

Cryo-L

Cryo-F

Input

Cryo-R

X-direction Y-directionX 方向

Y 方向

Analyzing of Response to ground motion

resonant frequency


9

Estimated Thermal BudgetEstimated Heat Loads at the radiation shields and Support posts and rods

70 W by the radiation at 80 K outer shield

2.2 W by the radiation at 8 K inner shield

24 W by the radiation and conduction (support posts and tension rods) at 80 K

2.4 W by the radiation and conduction (support posts and tension rods) at 8 K

Low Vibration Cryo-cooler unit

Very High Purity Aluminum Conductor (5N8)

Connection point with IM

dT2nd=0.5 K

94 K at the top of the 80 K outer shield

7.4 K at the top of the 8 K inner shield

47 K at 1st cold stage of Cryo-cooler 6.5 K at 2nd cold

stage of Cryo-cooler

dT1st = 26 K


10

Estimated Heat load

• Outer Shield (W)◦ Eleven View Ports 22◦ Radiation From 300 K 70◦ Support post and Rods 24◦ Electrical wires 3 x 10-4

Total 116W/unit 29

• 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 5.9W/unit 1.5

*Heat Load of Duct Shields will be presented by Mr. Sakakibara.

1st Cold stage

2nd Cold stage


Proto-type cryocooler unit under the performance test

Tri-axial laser displacement meter

Vacuum duct for very high purealuminum thermal conductorand radiation shield

Pulse tube type cryo-coolerwith anti-vibration stage


Vibration Level at edge of AL thermal conductor

VerticalPTC connectionAxial

HorizontalL=2 m


F.F.T. analysis (Ex. Axial F.F.T. analysis (Ex. Axial direction)direction)

Results of displacement at connection pointAxial < 200 nmVertical < 50 nmHorizontal < 10 nm


Cooling curve of proto-type cryo-cooler Cooling curve of proto-type cryo-cooler unitunit

Reachedlowest temp.2nd stage=4.8 K1st stage=37 K


Cooling Performance of Proto-type Cooling Performance of Proto-type Cryo-cooler UnitCryo-cooler Unit

Cooling Power per unit4.5 W at 8 K48 W at 75 K


Estimation cooling characteristics Estimation cooling characteristics Model is constructed to estimate initial cooling time 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

16Suspension from isolation system is excluded in this case

Y.SAKAKIBARA


Effect on Diamond Like Carbon coatingEffect on Diamond Like Carbon coating

17

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

Y.SAKAKIBARA


Production plan of LCGT mirror cryostats Production plan of LCGT mirror cryostats and peripheral componentsand peripheral components

Manufacture components

Assemble and factory test with cryo-coolers

Transport to Kamioka

Custody at Kamioka

2011 Jfy 2012 Jfy 2013 Jfy

‘12.3 ‘13.3 ‘14.3‘11.3

Design by KEK

‘11.09.20&21Contractors were decided;JEC- TohrisyaToshiba

We are here

Four Mirror Cryostats

Cryo-cooler units

Design by KEK

Proto-type Cryo-cooler unit test

Production of7 cryo-cooler units Production

of 9 cryo-cooler units

Transport to Kamioka

Custody at KamiokaPerformance test

Duct shield units

Design by KEK Production of Proto-type ducts shield units with cryo-coolers

Performance test


Vacuum duct1000 with radiation shield

Gate valve Gate valve

Connection Port to SASMirror a cryostat

Mirror Cryostats with the duct shields


L=~17 m

L=~17 m


Type-A (2-layer structure)

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

20

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.

21

An example of a cryogenic payload’s An example of a cryogenic payload’s drawing drawing

drawing by S. KOIKE drawing by S. KOIKE

22drawing by S. KOIKE drawing by S. KOIKE

A cryogenic payload in the cryostat A cryogenic payload in the cryostat

Main LASER beam


SummarySummary

23

• The performance of the cryo-cooler unit with anti-vibration 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

payload.


Back UPBack UP


MLI utilizes quite a lot of aluminized MLI utilizes quite a lot of aluminized thin polyester films as radiation thin polyester films as radiation shields.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 generalcharacteristics of out-gas rate at room temperature.


To reduce the total amount of out-To reduce the total amount of out-gas,gas,

Thickness of polyester film must be thin Light Weight MLI

Total number of films in MLI must be reduced High Thermal Resistance


SpecificationsSpecifications of Candidate of Candidate MLI MLI : KFP-9B08: KFP-9B08

m535

2m/gf121

1

( provided by Tochigi Kaneka Co., Ltd.)

*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

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 EmissivityLess than 0.1 for non-laminated side

Less than 0.6 for laminated side


Back ground(SUS Chamber)

The measurement is now The measurement is now underwayunderway

MLI : Kaneka KFP-9B08


(2) High Thermal Resistance(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 from thermal resistance point of view.

⇒ Light weight MLI


F.F.T. analysis (Vertical F.F.T. analysis (Vertical direction)direction)

Vertical


F.F.T. analysis (Horizontal F.F.T. analysis (Horizontal direction)direction)

Horizontal


Appendix(Conduction cooling ofAppendix(Conduction cooling ofsuspension system, No radiation)suspension system, No radiation)

Thermal conductivity of heat links or sapphire fibers limits cooling time

32


Appendix(Conduction and radiation Appendix(Conduction and radiation cooling of suspension system)cooling of suspension system)

33

Radiation dominates above 100 KConduction dominates below 100 K

Radiation


Incident Thermal Radiation through Duct Incident Thermal Radiation through Duct ShieldShieldandandCooling Time of MirrorCooling Time of Mirror

Yusuke SAKAKIBARA (ICRR)

342011.8.4 LCGT f2f meeting


Incident Thermal Radiation through Incident Thermal Radiation through Duct ShieldDuct Shield

35


Purpose of duct shieldPurpose of duct shield Thermal radiation from opening of 900 mm in diameter

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

◦ Problem experienced in CLIO

36

Cryostat Cryostat

Duct Shield

17 m

900 mm


Reducing thermal radiation by bafflesReducing thermal radiation by baffles Incident thermal radiation calculated using ray trace model by

counting up number of reflections

37

(Aluminum of A1070 measured at 10 um, 80 K)


Calculation of incident thermal radiationCalculation of incident thermal radiation Apertures of baffles change linearly

38

R=0.94±0.02Worse caseR=0.96 P=0.172 WBetter caseR=0.92 P=0.0615 W

Thermal radiation can be sufficiently reduced by baffles

R=0.94 at 10 um


Cooling Time of MirrorCooling Time of Mirror

39


SummarySummary

• Thermal radiation through duct shield can be sufficiently reduced by baffles

◦ 200 mW (100 mW x 2 duct shields)

It takes 20 days to cool down mirror with DLC coating

◦ Research for high emissivity coating is now underway

40


Calculation about incident heat through radiation Calculation about incident heat through radiation shields of LCGT ductsshields of LCGT ducts

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

41

ICRR ， KEKA


ContentsContents 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

42

Vibration Isolation System

Beam Duct

Laser BeamMirror(20 K)

Inner Shield(8 K) Outer Shield(80 K)

Schematic diagram of cryostat

S. KOIKE


Purpose of duct shieldPurpose of duct shield Thermal radiation from opening of 900 mm in diameter

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

43

Cryostat Cryostat

Duct Shield

17 m

900 mm

Solid Angle

29.2 W


Cooling test in LCGT prototypeCooling test in LCGT prototype（（ CLIOCLIO ）） Thermal radiation reflected by duct shield

◦ Experimentally verifiedT. Tomaru et al. Jpn. J. Appl. Phys. 47 (2008) 1771-1774

Incident power

　　 Calculated by tracing rays (reflectivity is 0.94) 600 times larger than considered from solid angle

44

Cryostat Cryostat

Duct Shield

17 m

900 mm

Solid Angle

29.2 W 6.22 W

Although "black" duct shield absorbs thermal radiation, it radiates itself.


Reducing thermal radiation by bafflesReducing thermal radiation by baffles Reflecting thermal radiation to room temperature side by baffles Increasing number of reflections of rays by baffles

45

Room Temperature Low Temperature


Calculation of incident thermal radiationCalculation of incident thermal radiation 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

46

: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


Comparison with experimental valueComparison with experimental value 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 of many reflections.

47

7 cm 2.3 cm

135 cm

117 cm3 cm

Baffle

Room Temperature Cryogenic Temperature


Calculation in LCGT caseCalculation in LCGT case Apertures of baffles change linearly

48

R=0.94 at 10 μm (reflectivity of duct and baffles) R=0.94±0.02(measured value of aluminum A1070 at wavelength 10 μm, 80 K)Worse caseR=0.96 P=0.283 WBetter caseR=0.92 P=0.100 W


Room Temperature Cryogenic Temperature

High absorptivity coating High absorptivity coating （（ DLDLCC ））

Baffles whose room temperature sides are coated with DLC (Diamond-Like-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◦ Reflectivity of cryogenic temperature sides of baffles 0.94

49

DLC coating

Heat absorbed by bafflesHeat load becomes smaller

Position of baffles x=0,10,14,16,17 mWithout DLC 0.163 WWith DLC 0.0883 W


Heat sources W◦ Radiation through duct shields 0.3 ◦ Eleven view ports 0.4 ◦ Radiation from outer shield 2.2◦ Conduction from supports 2.4◦ Absorption of laser by mirror 0.9◦ Scattering of laser by mirror ～ 3

Total ～ 9

Budget of thermal loads on 2Budget of thermal loads on 2ndnd stages stages of LCGT cryocoolersof LCGT cryocoolers

50S. KOIKE

N. KIMURA

Thermal radiation through duct shieldscan be sufficiently reduced by baffles


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

51


Appendix (Heat capacity)Appendix (Heat capacity)

52

Sapphire: Y.S.Touloukian: "Thermophysical Properties of Matter Volume 5 Specific Heat Nonmetallic Solids," IFI/Plenum (1970)Copper: AIST Network Database System for Thermophysical Property DataAluminum: NIST http://cryogenics.nist.gov/MPropsMAY/5083%20Aluminum/5083Aluminum_rev.htm


Appendix (Thermal conductivity)Appendix (Thermal conductivity)

53Sapphire: Y.S.Touloukian: "Thermophysical Properties of Matter Volume 5 Specific Heat Nonmetallic Solids," IFI/Plenum (1970)Aluminum: AIST Network Database System for Thermophysical Property Data


Appendix (Emissivity)Appendix (Emissivity)

54Sapphire: Y.S.Touloukian: "Thermophysical Properties of Matter Volume 5 Specific Heat Nonmetallic Solids," IFI/Plenum (1970)Copper: Y.Sakakibara et al. TEION KOGAKU 2011;46

Cryogenic System design of LCGT - Status of Cryogenic Design -

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