Plasma Wake Accelerators: Introduction and Historical Overview

Fundamental questions on the nature of matter and energy have found answers thanks to the use of particle accelerators. Societal applications, such as cancer treatment or cancer imaging, illustrate the impact of accelerators in our current life. Today, accelerators use metallic cavities that sustain electricfields with values limited to about 100 MV/m. Because of their ability to support extreme accelerating gradients, the plasma medium has recently been proposed for future cavity-like accelerating structures. This contribution highlights the tremendous evolution of plasma accelerators driven by either laser or particle beams that allow the production of high quality particle beams with a degree of tunability and a set of parameters that make them very pertinent for many applications.