Knudsen cell

In crystal growth, Knudsen effusion cells are often used as sources in evaporators for relatively low partial pressure elementary sources (e.g. Ga, Al, Hg, As). Because it is easy to control the temperature of the evaporating material in Knudsen cells, they are commonly used in molecular-beam epitaxy.

A typical Knudsen cell contains a crucible (made of pyrolytic boron nitride, quartz, tungsten or graphite), heating filaments (often made of metal tantalum), water cooling system, heat shields, and an orifice shutter.