Governing factors for production of photoemission-modulated electron beams

Abstract

Charged particle beams normally contain a complicated pulse shape structure when created. This structure is created by particular equipment and techniques such as high bandwidth laser systems driving photocathodes, and may drive effects that degrade beam quality or produce coherent electromagnetic radiation. While often encountered, such structure is generally poorly diagnosed and difficult to control. To study the effects of pulse shape structure in intense beams, we have developed a system using combined thermionic emission and photoemission to produce carefully tailored pulse shapes in an electron beam. In this paper, we discuss the performance of this system and derive limiting curves to explain the range of electron beam pulse shapes measured with it. Suggestions for improved design of future photomodulation systems are also made.