advantages of aluminum vacuum - indico.cern.ch

Advantages of Aluminum Vacuum

Jed Bothell

Atlas Technologies

April 2014

Presentation Outline


Properties of Aluminum Vacuum Mechanical Physical Surface Preparation and Cleaning

Manufacturing Considerations Machining, Extruding Joining: Welding, Brazing, Friction Stir

Aluminum Flanges & Fittings Atlas Flanges & Fittings Conventional O-ring seals

Economics of Aluminum

Summary



VACUUM PROPERTIES:

Lower levels of Hydrogen and Carbon desorption from Aluminum

• Aluminum has seven (7) orders of magnitude less Hydrogen

than in stainless steel 1

• Aluminum alloys have less carbon than stainless steel, including grade

316L

• Consequently reduced H2, CO, CO2 and CH4 outgassed species in

Aluminum

Able to reach UHV and XHV regimes, useful when working with Duterium

1. J.F. Norton, Trans. 8th AVS Vac. Symposium, pp.14 (1962)


VACUUM PROPERTIES:

Outgassing Rate

1. H. Ishimaru, JVST A 7(3), 2439 (1989)

2. H. F. Dylla, D. M. Manos, P. H. LaMarche, JVST A 11(5), 2623 (1993)

3. D. J. Stanteler, JVST A 10(4), 1879 (1992)

Condition Aluminum 1

Torr·l/sec·cm2

Stainless Steel 2, 3

Torr·l/sec·cm2

Unbaked (After 10hr Pumping)

1x10 -10 3x10 -10

Baked (After 24hr, 150°C Bakeout)

1x10 -13 6.3x10 -11


Cleaning and Surface Preparation

• Outgassing from vacuum surfaces minimized with,

dense, stable passivation layer 1

• Remove contaminated mill-scale oxide layer through

mechanical machining/abrasion and/or chemical

means.

• Allow dense oxide passivation layer to form.

• Bakeout at 150°C converts hydroxides and oxides in

to stable oxide.

1. J Garner, Handbook of Vacuum Technology, pp.509 – 552, Academic Press (1997)


MECHANICAL PROPERTIES Deflection Thickness of Flat Plate Calculation*: tp = (kPrp

4/(Ed))1/3

Since the Modulus of Al is 1/3 of SS:

tAS = (ESS/EAl)1/3 = (19,000/7,474) 1/3 = 1.36 x SS

Aluminum Chambers need only be ~1.5x thicker than Stainless to maintain the same or less deflection

tp = Thickness of plate k = .0696 if Clamped, or = 0.171 of clamped P = Atmospheric Pressure rp = Radius of circular plate or small side of rectangular plate E = Modulus of Elasticity: Al = 7,474 Kgf/mm2 & SS = 19,000 Kgf/mm2 d = Acceptable deflection tAS = Acceptable deflection

* Mark’s Standard Handbook For Mechanical Engineers, by Avallone, E.A. and Baumeister, T; Ninth Edition, 1978 pp 5-52.


MECHANICAL PROPERTIES ...

Aluminum is Light Weight 1/3x the weight of stainless steel

Uses - Minimizing floor structure in clean rooms

- Portable chambers

- Mechanically manipulated chambers

- Ease of handling

- Large chambers

Physical Properties Aluminum

6061-T6 Stainless Steel

304

Thermal Conductivity W/mK

167 16.2

Density g/cc

2.7 8.03

Modulus of Elasticity GPa

68.9 193


Mechanical Properties…

Aluminum has a Lower Young’s Modulus

1/3 that of stainless steel

Aluminum chambers absorb vibration better

Useful for optics (photon, electron, …)

Inspection tools (wafer repair, )

Physical Properties

Aluminum 6061-T6

Stainless Steel 304

Thermal Conductivity W/mK

167 16.2

Density g/cc

2.7 8.03

Modulus of Elasticity

GPa 68.9 193


PHYSICAL PROPERTIES: Thermal Conductivity

Aluminum Has a Very High Thermal Conductivity

10x the thermal conductivity of Stainless

21x the thermal diffusivity

Uses

- Faster and more complete bakeout

- Even bakeout (no condensing cold spots)

- Thermal chambers



304

Thermal Conductivity

W/mK 167 16.2

Density g/cc

2.7 8.03


68.9 193


PHYSICAL PROPERTIES : Thermal Conductivity Cont. Aluminum consequently has Low Thermal Gradients

-10W of heat from 6mmᶲ feedthrough on 1mᶲ x 6mm thick plate rises temp to: 6.6C in Al V.S. 83.8C in SS

Fast Thermal Time Constants - Evenly spaced heating/cooling tubes 20cm apart produce a thermal time constant of 1min Al V.S. 19min SS

PHYSICAL PROPERTIES: Thermal Emissivity Aluminum Has a Very High Thermal Emissivity 10x that of stainless steel Aluminum does not readily absorb radiant heat or radiate heat - Useful for Cryogenic Dewar's & cryostats & telescopes



304

Thermal Emissivity .04 -.07 .3-.7

Density g/cc

2.7 8.03


68.9 193


Other Physical Properties… Non-Magnetic: - Useful for electron optics μ Al = 1.000022 μ Austenitic SS = 1.003–1.007 μ Martinsitic SS= 49-95 (work hardened) Can be anodized: - Protects against many corrosives & halogens - Not ideal for high vacuum however Low Z (Low Neutron Nuclear Activation): - Low residual radioactivity… - X-ray transparent (relatively) - Neutron transparent (relatively)

Aluminum Alloys / Versatile Material

Aluminum is available in many alloys with a wide variety of properties

Wrought Alloy Principal Alloying

Element Heat Treatable General Comments Vacuum Comments

1xxx 99% Al No Good chemical resistance, poor strength Excellent

2xxx Cu Yes Good strength to weight ratio, poor corrosion properties Excellent

3xxx Mn No Moderate strength, good workability, used for cans Excellent

4xxx Si No Low melting temperature, used for welding fillers Excellent

5xxx Mg No Work hardens, good corrosion resistance Excellent

6xxx Mg-Si Yes Reasonable balance of strength to corrosion resistance Excellent

7xxx Zn Yes Very high strength, moderate corrosion resistance High Zn can pose problems


Advantages of Aluminum Vacuum MANUFACTURING ADVANTAGES:

Vacuum chambers of almost unlimited design possibilities…

• Plate-to-Plate

• Cylindrical

• Formed

• Monocoque (form solid billet)

• Extruded

Large Plate-to-Plate Chambers

Custom plate-to-plate

chamber manufactured

for NASA


Monocoque (Billet) Chambers

MANUFACTURING

ADVANTAGES:

Monocoque chambers are

machined from single piece

solid aluminum billet or

thick plate.


Spherical Hemispherical Chambers

MANUFACTURING

ADVANTAGES:

Just like stainless spherical

chambers are spun thin

plates of aluminum.


Joining Aluminum:

MANUFACTURING :

Aluminum brazing & welding technology is well understood with

many techniques:

-TIG (Tungsten Inert Gas) welding

- EBW (Electron beam welding)

-Brazing

- Vacuum

- Dip

- FSW (Fiction stir welding)

-Explosion bonding


Welding Aluminum

MANUFACTURING:

TIG Welding Aluminum:

- Design must account for

significant distortion after welding

- TIG Welds can generally not be

Machined and still hold vacuum

we recess welds if post machining

is required


Welding Aluminum

TIG Welding Aluminum:

Unlike TIG Welding Stainless:

- Due to high thermal conductivity

Try to weld similar masses

not thick to thin

- Aluminum TIG weld generally

require filler.


Welding Aluminum

Friction stir welding: Can be machined reliably and still be UHV quality


Brazing Aluminum

Vacuum brazing:

Clean & well suited for vacuum

products. Can not be easily

touched up with TIG welding later

Dip brazing:

Intricate aluminum assemblies can

be dip brazed in molten salts, can

be difficult to clean however


Atlas Flanges

EXW Explosion Welding (Bonding)

• Point source progressive discharge is detonated

• Plates are accelerated to contact each other

• Plasma is formed at the contact point, stripping surface oxides and contaminants

• Extreme pressures at impact form metallic bond

• Interlayers prevent intermetallic formation


Atlas ATCR fittings:

All Metal Face Seal Fittings for

Aluminum:

Compatible with standard Swagelok

VCR fittings

http://atlasuhv.com/images/uploads/content-full/atlas_atcr_exw_schematic_800px.jpg

Atlas ATCR fittings:

Atlas Chamber Mount:

Welded from inside the vacuum

vessel

The Robust female nut prevents

damage while in use on the

chamber

http://atlasuhv.com/images/uploads/product-images/atcr_chamber_mount_800px.jpg

Standard Aluminum O-Ring Sealed Flanges


ECONIMICS: Material pricing: Aluminum is by far less expensive than Stainless. • Aluminum ~$3.00 / lb • Stainless 304 ~$6.00/ lb & 316L ~$7.00/ lb Al needs to be ~1.5X thicker, but is 1/3 the density, therefore… Aluminum is ~$4.5 V.S. Stainless ~$17.8 – $20.8 for the same structural value

Stainless is ~ 4 X Aluminum per structural equivalent members


ECONIMICS:

Machining & labor pricing:

Aluminum is less expensive than Stainless.

Manufacturing costs can be significantly less

expensive:

–Aluminum machines 5 X faster than Stainless


ECONIMICS:

General Rule Aluminum chambers can be less

expensive than those made of SS when they…

• Have intricate and/or extensive machining

• Are larger than about three (3) cubic feet

• Can be manufactured using plate material

• Can be extruded

• Have multiple o-ring seals

• Superior vacuum properties of Aluminum enable

cost savings in pumping components


ECONIMICS:

Cost of Ownership (COO) of Aluminum chambers

can be lower than Stainless

• Vacuum pumps can be smaller –Because there is less H2, C and byproduct gasses

• There is less need for special H2 getter & water pumps –Because there is less H2, C and byproduct gasses

• Shorter bake time –Once baked Aluminum pumps much faster than SS

Summary

Reasons to use aluminum…

• Lower vacuum surface outgassing

• Lower Hydrogen permeability

• Efficient bakeout

• Excellent machinability

• Large and complex shapes

• Specific Properties

(magnetic, nuclear, chemical…)

• Light weight

• Lower cost

Repented in Scandinavia by:

Low2High Vacuum Box 9084, S-400 92 Göteborg

Sweden

Tel +46 31 68 84 701 Tel Tel +46 31 68 39 39 FAX

[email protected]

www.Low2High.se

Advantages of Aluminum

Vacuum

Thank you for your attention!

& Thank you

Svenska Vakuumsällskape

Appendix


VACUUM PROPERTIES:

Unbaked System

• Desorbing H2O dominates gas load of both stainless steel and aluminum

• Approximately similar outgassing rate for aluminum and stainless steel

Baked System

• Water desorbs much faster from aluminum than stainless steel

• Baking aluminum at 150°C is more effective than baking stainless steel at

much higher temperatures 1

• Bakes out faster and more completely than stainless steel

1. J Garner, Handbook of Vacuum Technology, pp.509 – 552, Academic Press (1997)

Atlas Customers — Physics & Accelerators

ANL Argonne Lab

BNL Brookhaven Lab

CAMD Louisiana State University

FNL Fermi Lab

JNL Jefferson Lab

LANL Los Alamos Lab

LBNL Lawrence Berkeley Lab

LLNL Lawrence Livermore Lab

NASA National Aeronautics &

Space Administration

SLAC Stanford Linear Accelerator

BESY Germany

CERN Switzerland

DESY Germany

ESRF France

KEK Japan

MP Germany (Max Plank)

Soleil France

NSRRC Taiwan

And many, many more!

Atlas Customers — Semiconductor, FAB and Solar

Applied Materials

Novellus Systems

Tokyo Electron

Ovonic ECD

Maxim

Toshiba

KLA

Cymer

Perkin Elmer

Vergeson

Varian

IBM

General Electric

Unaxis

Intel

Universal Display

Zilog

Ulvac

Aixtron Genus…

And many, many more!

World Leaders in Aluminum Vacuum

Be sure to request our latest catalogs…

• Atlas Flanges & Fittings 48-Page catalog

• Atlas Vacuum Chambers

12-Page Catalog

Welcome to the aluminum revolution!

The Aluminum vacuum

revolution has started —

In a remote corner of

Washington State,

in the rain shadow of the

Olympic Peninsula,

nestled along Puget

Sound, USA

Atlas delivers the aluminum revolution!

Modern aluminum vacuum components — with

lower cost and superior vacuum performance.

• Standard Flanges & Fittings

• Chambers

• Engineering & Technical Services

Atlas Flanges

Stainless Steel / Aluminum Bond Interface

• UHV rated to 1x10 -13 Torr

• Leak tested to < 1x10 -9 cc/sec of He

• Thermal Rating Peak — 300°C (during weld-up) Operational — (-)200°C to 250°C

• Mechanical Rating Tensile — 15,000 psi (103 Mpa) Shear — 10,000 psi (69 Mpa)

Atlas Standard Components

Aluminum & Aluminum/Stainless Products

Atlas CF and Wire-Seal flanges, ATCR tube fittings,

ISO Quick-Release / ISO Claw & Bolt flanges,

Pyrex Viewports, Tube & Pipe Transitions,

Neutron Windows, Quick-Disconnect,

Elbows, Tees and Crosses, Gaskets,

Fasteners, and more.

Bimetallic Flanges / Fittings

Available in all sizes and types…

• CF Flanges in US, Metric and ISO

• Flush, Tube and Weld-Neck mounts

• Rectangular

• Custom size and shapes

• Atlas ATCR TM metal-seal tube fittings… Swagelok VCR and Parker-Hannifin VacuSeal compatible

Advantages of Aluminum Vacuum Aluminum advantages depend on the vacuum regime

• At low vacuum the advantages are mainly cost

• At high and ultra high vacuum aluminum offers many technical

advantages

• There are also many special physical properties that make it an

excellent choice

Atlas Flanges

UHV flange couplings require…

• Knife-edge sealing (metal gaskets)

• Matching of thermal expansion properties

Solutions…

Hard coated aluminum knife-edge (TiC with Al gasket)

• Longevity is an issue

• Problematic during thermal cycling (bakeout)

Atlas CF Flange TM (Bimetallic)

Stainless steel knife-edge (Cu gasket)

• Aluminum flange body

advantages of aluminum vacuum - indico.cern.ch

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