摘要 |
<p>The invention relates to an electron beam generator for generating an electron beam, comprising an electron source and an extractor. The combination of electron source and extractor in use forms a negative lens, wherein said extractor has a positive voltage with respect to the source. The extractor and the electron source are positioned such that, in use, a space charge limited region is present between them. In an embodiment, the extractor is a planar extractor. In another embodiment, the source is a thermionic source.. The generator may comprise an illumination system for collimating the electron beam.</p> |