A sputter ion pump is made of arrays of stainless steel anode cells between titanium cathode plates, held at 3 to 7 kV in a magnetic field of about 0.1 to 0.2 T. Electrons trapped in the cells ionize gas, and the ions slam into the cathodes, burying themselves and sputtering fresh titanium that chemically traps active gases. It is silent, vibration-free and oil-free, reaches UHV and doubles as a gauge because its current tracks pressure, but it needs a starting pressure below about 10⁻⁵ mbar.
Ion pump current fell off a cliff after the bake and the B-A agrees, we're in the 10 to the minus ten range.
The pump current doubles as a free pressure gauge, but at very low pressure field-emission leakage current sets a floor, so the reading stops tracking real pressure.
Also heard as
- sputter ion pump
- SIP
- VacIon
Related terms
Argon instability
Periodic pressure bursts in a diode ion pump as buried argon is released again from the cathodes.
Getter
Reactive material that removes gas from a vacuum by binding it chemically to a fresh metal surface.
UHV
Ultra-high vacuum: pressures below about 10⁻⁷ mbar, reached only with baked, metal-sealed systems.
TSP
Titanium sublimation pump: a heated titanium filament that coats nearby walls with a fresh gettering film.