OVERVIEW OF HIGH-BRIGHTNESS ELECTRON GUNS*

Abstract

In most electron linear accelerators, the beam brightness is set by the beam source. It is very difficult to improve the overall beam brightness after it has been produced; on the other hand, providing a brighter beam source can provide an “instant upgrade ” to the performance of a brightness-limited electron-linac-based facility. The development and routine operation of high-brightness guns, therefore, is critical to the success of next-generation linac-based light sources. This includes sources already under construction, as well as proposed and as-yet completely theoretical machines. In recent years, other potential applications of high-brightness electron beams have been identified, including high-average-power IR and UV free-electron lasers, an