Advantages of Aluminum Vacuum - indico.cern.ch
Transcript of Advantages of Aluminum Vacuum - indico.cern.ch
Advantages of Aluminum Vacuum
Jed Bothell
Atlas Technologies
April 2014
Presentation Outline
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
Advantages of Aluminum Vacuum
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)
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
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)
Advantages of Aluminum Vacuum
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.
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
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
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
Advantages of Aluminum Vacuum
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
Physical Properties Aluminum
6061-T6 Stainless Steel
304
Thermal Emissivity .04 -.07 .3-.7
Density g/cc
2.7 8.03
Modulus of Elasticity GPa
68.9 193
Advantages of Aluminum Vacuum
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
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
Advantages of Aluminum Vacuum
Monocoque (Billet) Chambers
MANUFACTURING
ADVANTAGES:
Monocoque chambers are
machined from single piece
solid aluminum billet or
thick plate.
Advantages of Aluminum Vacuum
Spherical Hemispherical Chambers
MANUFACTURING
ADVANTAGES:
Just like stainless spherical
chambers are spun thin
plates of aluminum.
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
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.
Advantages of Aluminum Vacuum
Welding Aluminum
Friction stir welding: Can be machined reliably and still be UHV quality
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
Atlas ATCR fittings:
All Metal Face Seal Fittings for
Aluminum:
Compatible with standard Swagelok
VCR fittings
Atlas ATCR fittings:
Atlas Chamber Mount:
Welded from inside the vacuum
vessel
The Robust female nut prevents
damage while in use on the
chamber
Standard Aluminum O-Ring Sealed Flanges
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
ECONIMICS:
Machining & labor pricing:
Aluminum is less expensive than Stainless.
Manufacturing costs can be significantly less
expensive:
–Aluminum machines 5 X faster than Stainless
Advantages of Aluminum Vacuum
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
Advantages of Aluminum Vacuum
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
www.Low2High.se
Advantages of Aluminum
Vacuum
Thank you for your attention!
& Thank you
Svenska Vakuumsällskape
Appendix
Advantages of Aluminum Vacuum
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