Gigavolt-per-Meter Wakefields in Annular Dielectric Structures

A wakefield accelerator uses a medium capable of sustaining appropriate electric fields to transfer energy from a drive beam to a witness beam. Examples of such systems include electron beam driven plasma wakefields, laser driven plasma wakefields and electron beam driven dielectric wakefield structures. Dielectrics and plasmas are of particular interest because they are capable of maintaining electric fields on the order of GV/m and in the case of plasmas upwards of TV/m. These systems provide a significant step beyond current radiofrequency accelerating structures capable of peak electric fields on the order of 100 MV/m and average effective electric fields of 20 MV/m. Furthermore, beam driven dielectric structures produce a wakefield which is phase synchronous with the beam, these structures do not suffer from transit time or dephasing effects. In the case of dielectric wakefield accelerators, the structures under study in this publication, the modes generated by the driving beam are in the terahertz (THz) regime. Thus development of dielectric wakefield accelerators is seen as a path to smaller, more compact accelerating systems and as a means to generate THz radiation. Here we demonstrate a beam-driven dielectric wakefield accelerating structure that produces sustained fields of 1.35 GV/m for many hundreds of thousands of drive beam pulses. In addition we show beam-driven dielectric structures have the potential to produce single mode, high spectral purity THZ radiation of unprecedented energy scale