gwadw2011 elba/italy, 26/may/2011 n. kimura refrigerator and cryostat design for lcgt n. kimura a,...

GWADW2011 Elba/Italy, 26/May/2011 N. KIMURA

Refrigerator andRefrigerator andCryostat Design for LCGT Cryostat Design for LCGT

N. KIMURAA, T. SUZUKIA, S. KOIKEB,

T. KUMEB, T. OHMORID, K. SASAKIA,

Y. SAITOC, Y. SATOC, H. YAMAOKAC

and LCGT CollaborationA Cryogenics Science Center/KEKB Mechanical Engineering Center/KEKC Accelerator Laboratory/KEKD Teikyo University

KEK: High Energy Accelerator Research Organization

GWADW2011 Elba/Italy, 26/May/2011 N. KIMURA2

Outline

• LCGT cryogenics Cooling option for the Mirror

Thermal Analysis

Mechanical Analysis

Materials (New MLI for LCGT)

• Summary


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 with four cryocooler unitsCryostat with four cryocooler units

Structure of Mirror Cryostat


Basic requirements from the LCGT Basic requirements from the LCGT cryogenicscryogenics

• Temperature of the test mass/mirror : 20 [K]

Inner radiation shield have to be cooled to < 8 K

• Cool the mirror without introducing excess noise,

especially vibration due to cryo-coolers.

• Easy access and enough space

for installation work around the mirror.

• Satisfy ultra high vacuum specification < 10-7 PaI was requested make a design for the LCGT I was requested make a design for the LCGT cryostat cryostat from ICRR just One year ago!from ICRR just One year ago!

ISSUESISSUES

Estimated by Dr. Uchiyama (ICRR)


Cooling Cooling OptionOption

Vibration Reduction

Stage

HeatLink

VRSCold Stage

Our decision: Use CLIO type Cryo-coolerOur decision: Use CLIO type Cryo-coolerwith low vibration mount for LCGTwith low vibration mount for LCGT


Advantage and Disadvantage of Advantage and Disadvantage of CLIO type cryocooler unitCLIO type cryocooler unit

AdvantageBasic concept of design has been established since

the R&D done in CLIO. (2001~2003)

DisadvantageSome critical components are unavailable today.

Reasons are in the followings. ◦ Withdrawal business by social condition◦ A change of generation of experienced workers◦ Replace or renewal of the equipment of a factory

We have to find substitutes!

Disappeared ItemsReady to use Cryo-Cooler equipped special cold

stage, such as CLIO typeAluminum FRP tube as anti-vibration support

rodsHigh pure aluminum thin wire less than 0.12

mmfor heat link.

Substitutes for the ItemsAttach new design of cold stage flanges

to mass-produced 1W/4K PTCReplace to Carbon FRP tube as anti-vibration

support rods (stiffness AFRP > CFRP > GFRP)Start R&D work with new company

for development of high pure aluminum thin wire less than 0.12 mm.


Other Candidate Other Candidate => re-condensation cryo-cooler => re-condensation cryo-cooler

Field quality is sensitive to relative position btw yoke and coil

random & individual vibration due to mechanical resonance

-> disturb uniform field

It needed more R&D worker than to find substitutes materials for the new CLIO type cryo-cooler,when the project was started.

Example; SCGR meter, g-2 project at J-PARCThe g-2 SC magnet is required with very high magnetic field uniformity below the level of 0.1 ppm.


An Estimated Break Down List of Thermal Budget

• 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 was presented by Mr. Sakakibara on Monday.

1st Cold stage

2nd Cold stage


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)


40,000 W/m/K @ 6K

6N Aluminum

2N Aluminum~Type A-1070

Example of Thermal Conductivity of 6N-class Very High Pure Aluminum*

For inner shield

For outer shield

5N up AlRRR=3000

We must put the right material in the right position.

Cost:5N8 > 2N Aluminum


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

< 8 K at Connection point with IM

dT2nd=0.5 K

94 K at the top of the 80 K outer shield (A1070)

7.4 K at the top of the 8 K inner shield (5N8+A1070)

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

stage of Cryo-cooler

dT1st = 26 K


*PTC: Pulse Tube-type *PTC: Pulse Tube-type CryocoolerCryocooler

dQ=2 W

5W/50W

4W/40W

Heat load/Unit= 400 kW * 20 ppm / 4 units = 2 Heat load/Unit= 400 kW * 20 ppm / 4 units = 2 W/unitW/unit

Rough Estimation of the PTC* operationRough Estimation of the PTC* operationwith 20 ppm deposition by Scattering Light at 400 kWwith 20 ppm deposition by Scattering Light at 400 kW

20 ppm deposition may be accepted,20 ppm deposition may be accepted,but we lost contingency cooling power of 2 W.but we lost contingency cooling power of 2 W.

11 K

23 K


Doors for access to insideDoors for access to inside

Inner shield

S. Koike

Outer shieldW 1600 mm X h 1900 mmW 1020 mm X h 1600 mm


Static deformation analysisStatic deformation analysis

Main vacuum duct and the duct to SAS are not connected. Boundary conditions

◦ periphery of the bottom : fix

S.Koike


Modal Modal analysisanalysis

Resonance Frequency

S.Koike

Boundary condition: fix the perimeter of the bottom

* Interface to SAS is not fixed at the moment.


Structure of Structure of Radiation Radiation ShieldsShields

Outer ShieldsOuter Shields Inner ShieldsInner Shields

Flame by Flame by A6000A6000AluminumAluminum

Secure stiffnessSecure stiffnessof the radiation shieldsof the radiation shields


Modal analysis of outer shieldModal analysis of outer shield

M=

Mode frequency

M=

S.Koike

Remove support rodMode Frequency


Modal analysis of inner shieldModal analysis of inner shieldS.Koike

M=

Frequency


Response to ground motion Jan. 31st,2011H. Yamaoka

Input to peripheral of bottom

Mozumi 50m K.Y. 2005

Cryo-top

Cryo-L

Cryo-F

Input

Cryo-R

X-direction Y-directionX 方向

Y 方向

Response to ground motion


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


SummarySummary

26

The design of the mirror cryostat for LCGT satisfying requirements was almost finishedin one year.

The production of the components for the cryostat will be started after contractor decided.

Performance of the first cryostat will be demonstrated on the mid of 2012 Jfy.

Proto type cryo-cooler units replaced with substituted materials will be completed on the end of this June.

Performance of the first cryo-cooler will be confirmed on the mid of this July.

gwadw2011 elba/italy, 26/may/2011 n. kimura refrigerator and cryostat design for lcgt n. kimura a,...

Documents

polyester films

thickness of polyester

motiongwadw2011 elbaitaly

conduction term qc

qr qc radiation term

reflective films

mli qt

contact pressure