Linde process
Cooling of gas (e.g. air) under high pressure using counterflow with subsequent throttling causing a liquid to form

Liquefier
Low-temperature system which cools gas from ambient temperature and liquefies it (in contrast to refrigerating plant

Neon adsorber
Cleaning step in a low-temperature system using adsorption at around 20 K (neon is used for preference, but also hydrogen, for example)

Nitrogen adsorption
Cleaning step in a low-temperature installation using adsorption at approx. 80 K (adsorbing nitrogen for preference, but also oxygen, methane, etc.)

Normal hydrogen
Balanced form of hydrogen at ambient temperature (25% para and 75% ortho)

Oil diffusion pump
Generates high vacuum by entrainment of residual gas molecules through condensation of oil

Ortho hydrogen
Modification of hydrogen with parallel spins

P&I diagram
Pipework and instrumentation diagram for a processing plant

Para hydrogen
Modification of hydrogen with antiparallel spins

Penning tube
Vacuum gauge for measurement of vacua from 10-4 to 10-8 mbar

Pirani gauge
Vacuum gauge for measurement of vacua from ambient pressure to 10-4

Power lead (of a magnet)
Power cable of a superconducting magnet (made of copper with connector to the superconducting material); must be actively cooled to prevent heat incidence

ppm
Parts per million: used to measure contaminants (in terms of volume or weight)

PSA
Pressure swing adsorber: cleaning step using adsorption, with regeneration through pressure release (in contrast to TSA, where T = temperature)