Ultra-High Vacuum Compatible Electron Source
Original Publication Date: 1985-Apr-01
Included in the Prior Art Database: 2005-Feb-18
The evaporation of low vapor pressure compounds, such as refractory metals under ultra-high vacuum (UHV) conditions, is difficult due to outgassing from the electron source or E-gun and the surrounding parts. The sources of outgassing which result from excess heating can be eliminated by a thorough outgassing and by building all parts from materials, such as Mo, W or Ta. However, outgassing due to desorption of gas molecules from chamber walls because of electron bombardment has been a problem heretofore. The use of electrostatic E-guns, which have a cage at -10 KV around them, operates to prevent most of the electrons from escaping from the gun. The principles of operation are demonstrated in the figure which shows a concentrically symmetric electrostatic E-gun.