L–Introduction to Materials for Ultra-High Vacuum (UHV) Applications

In ultra-high vacuum (UHV) environments, where pressures can drop below 10^{-9} Torr, the choice of materials is critical to maintain the vacuum and ensure the stability of experiments or processes. Key considerations for UHV materials include low outgassing, thermal stability, mechanical strength, and chemical resistance.

Outgassing refers to the release of gases trapped or adsorbed on material surfaces, which can degrade the vacuum. Materials like stainless steel, aluminum, and copper are commonly used due to their low outgassing properties and mechanical durability after proper cleaning and bakeout. For components such as seals, Viton and Kapton provide a balance of flexibility and low outgassing, though they are used with temperature limitations. Materials like Teflon are less suitable due to their relatively high outgassing.

Careful selection and preparation of materials are vital for maintaining the integrity of UHV systems. Here is a list of materials to consider:

Material	Outgassing (Torr·L/s/cm²)	Melting Point (°C)	Tensile Strength (MPa)	Thermal Expansion Coefficient (10⁻⁶/°C)	Thermal Conductivity (W/m·K)	Example Use Cases
Aluminium (6061-T6)	3 × 10⁻¹¹	582	310	23.1	167	Beam Tubes, Support Structures
Invar (36)	2 × 10⁻¹³	1450	490	1.2	12.5	Dimensional Standards, Precision Instruments
OFHC Copper	1 × 10⁻¹²	1083	210	16.5	398	Gaskets, RF Shields
Stainless Steel (304L)	1 × 10⁻¹²	1450	515	16.0	16.2	Chambers, Flanges, Support Structures
Titanium	5 × 10⁻¹²	1668	900	8.6	21.9	Pumps, Fasteners
Alumina (Ceramic)	1 × 10⁻¹³	2050	300	8.0	30.0	Insulators, Feedthroughs
Borosilicate Glass	1 × 10⁻¹²	1510	69	3.3	1.2	Viewports, Windows
Kapton (Polyimide)	5 × 10⁻¹¹	500+ (decomposes)	231	20.0	0.12	Cable Insulation, Thermal Barriers
PEEK (Polyether Ether Ketone)	5 × 10⁻¹⁰	343	90	47.0	0.25	Insulators, Structural Components
Teflon (PTFE)	1 × 10⁻⁷	327	23	100.0	0.25	Insulators, Gaskets, Seals
Viton (Fluoroelastomer)	1 × 10⁻⁹	200 (decomposes)	N/A	N/A	0.25	O-Rings, Seals

For more detailed information, you can explore these resources:

To Be Added

By understanding the properties and limitations of materials used in UHV, you will be better equipped to design and operate high-vacuum systems effectively.