Feasibility of a Plasma-Filled Inverse Free Electron Laser Accelerator

A high power millimeter (mm) wave, in the presence of a magnetic wiggler, produces a large longitudinal ponderomotive force that can accelerate electrons. When a plasma of density n ~ ncr, where ncr is critical density, is introduced in the interaction region, the ponderomotive force resonantly drives a plasma wave that accelerates electrons to higher energies. However, propagation of the mm wave requires a guide magnetic field; O-mode requiring less field than the X-mode. The plasma wave in this situation goes over to the upper hybrid (UH) mode. A parabolic plasma density profile with minimum on axis provides guiding for the mm wave as well as the UH wave, the latter being more strongly localized than the former. The UH wave, for typical parameters, can accelerate electrons to several tens of megaelectronvolts.