A low-energy low-density electron beam diagnostic for large amplitude relativistic plasma waves

Abstract

The interactions of a low-energy electron beam that is injected perpendicularly through a large amplitude relativistic plasma wave are considered computationally. As the beam passes through the electrostatic fields of the plasma wave, its transverse profile becomes distorted. The amount of distortion provides information on the magnitude of the electrostatic field, as shown by particle trajectory simulations. The sensitivity and advantages of this low-energy beam diagnostic are compared with that for a relativistic electron beam diagnostic. The limit on the beam density required to prevent the growth of two stream instabilities is addressed. Implications for the use of this method as a diagnostic for ultrahigh-gradient plasma wave accelerators are discussed.