Production and Use of Femtosecond Electron Bunches

Abstract

Sub-picosecond electron pulses are desired in a variety of applications. Such bunches can, in principle, be obtained in large, high energy electron linear accelerator systems by repeatedly applying an energy slew and magnetic compression. Another process is the production of short electron pulses at low energies. An rf-gun with a thermionic cathode together with a bunch compressing a-magnet can serve as such a source. Although such sources have been constructed and are operating, a systematic analysis of capabilities and limits has not been performed yet. In this paper, we discuss the particular parameter choices to generate femto-second electron bunches from an rf-gun. The impact of geometric and electric specifications on the 6-dimensional phase space distribution of the electrons are investigated through numerical simulations with the particle-in-cell code PARMELA. Specifically, this includes effects and limitations due to space charge forces. While the production of femtosecond electron bunches is of primary concern, we also consider the preservation of such short bunches along a beam transport line.