Titanium Sublimation Pumps
The Titanium Sublimation Pump is a true UHV pump, it is used to supplement the pumping action of other UHV pumps (normally Ion pumps) as it can be more effective at pumping certain gases. The main advantage of this pump is that it is simple, low cost, and can give a high pumping speed.
Principle of Operation.
The ZST22 Titanium Sublimation Pump (TSP) 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 such that it glows red hot, at this temperature Titanium is sublimated directly from the filament (Ti vapour is produced from solid without becoming the liquid phase). This sublimated evaporant then coats the nearby walls of the chamber.
The chamber wall should be designed to have a large surface area, the resultant clean Titanium film reacting with the active gas molecules to form low vapour pressure compounds (i.e. the gases are effectively removed). Once the film has reacted it must be replaced by re-evaporation from the TSP. The time gap between these regenerative evaporations depends on the pressure of the system and the gas types being pumped. It can be anything from almost continuous (at 10-5 mbar) to once every 12 hours (in the 10-11 mbar region).
To enhance the pumping speed of the Titanium film, the condensing wall can be cooled to liquid nitrogen temperatures. The table below shows the difference in pumping speed for a surface at room temperature, and a surface at -196°C. It should be noted that this reservoir must be carefully designed to give a maximum surface area in the region of the Ti film so as to maximise pumping speed.
- Large Diameter Ti Filaments
- High sublimation rate
- Robust construction with replaceable clamps and insulators
- Filaments easily replaced
- Special insertion lengths made to order
