Purity |
≥99.9995% (6.0 grade) or ultra-high-purity ≥99.9999% (7.0 grade), with trace impurities (e.g., O₂, N₂ ≤ 0.5 ppm) |
Key Applications |
– Cryogenics: Cooling superconductors in MRI machines and particle accelerators |
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– Aerospace: Pressurizing rocket fuel tanks and purging engines |
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– Semiconductors: Carrier gas in photolithography and etching processes |
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– Research: Leak detection, gas chromatography, and fusion reactors |
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– Welding: Shielding gas for non-ferrous metals (e.g., aluminum) |
Physical Properties |
– Boiling point: -269°C (4.2 K, lowest of any gas) |
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– Low density (0.1785 g/L at STP) and high thermal conductivity |
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– Chemically inert (non-reactive) |
Safety Precautions |
– Non-toxic but displaces oxygen (risk of asphyxiation in confined spaces) |
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– Extreme cold hazard (liquid helium at -269°C requires cryogenic gloves) |
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– Avoid inhalation (voice alteration risks, though temporary) |
Storage & Handling |
– Compressed gas cylinders (e.g., 50L, 100L) at 137–200 bar pressure |
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– Dewar flasks for liquid helium (up to 10.000 liters) |
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– Store upright in well-ventilated areas away from heat/flammables |
Certifications |
Compliance with ISO 7291 (gaseous helium), ASTM D7673. and medical/FDA regulations for MRI use |