Titanium Sublimation Pumps (TSP) are true UHV pumps.   They are used to supplement the pumping action of other UHV pumps (normally ion pumps and turbo molecular pumps) as they can be more effective at pumping certain gases.   Titanium Sublimation Pumps consists of 3 removable hairpin shaped filaments.   They are made from an alloy of titanium and molybdenum and are mounted in a simple carrier designed to have low electrical resistance.   A high current, from an external power supply, is passed through the filament so that it glows red hot.   At this temperature, titanium is sublimated directly from the filament.   This sublimated evaporant then coats the nearby walls of the chamber.