Physics Colloquium: Surfing on an electric wave

Prof. Alec Thomas, University of Michigan

Tuesday 03 November 2015, 1100-1200
Lecture Theatre 2, Fylde College

In laser wakefield acceleration (LWFA) an electron bunch “surfs” on the electron plasma wave generated by an intense laser pulse. The plasma wave has a strong longitudinal electric field that stays in phase with the relativistic driver and is therefore an ideal structure for accelerating charged particles. The principal benefit of plasma based accelerators is the absence of a breakdown electric field limit, because the medium is already ionized. Over the last decade, LWFA has been a very successful technique for accelerating electrons, with experiments demonstrating accelerating gradients in excess of 100 GeV/m by many groups around the world. Conventional RF accelerators are restricted to accelerating gradients many orders of magnitude lower.

Electron beams generated by LWFA also have other desirable properties, such as small emittance and ultrashort duration, that arise naturally in the acceleration process. These attributes suggest that LWFA has great potential as an advanced accelerator concept, for industrial, medical and engineering applications as well as future colliders for high energy physics. Although highly competitive in terms of accelerating gradient, however, results from LWFA experiments need improvement to compare with the state-of-the-art in conventional accelerators in terms of important characteristics; in particular, beam energy spread, repetition rate and stability. I will present results from experiments on laser systems at the University of Michigan that attempt to address some of these issues and demonstrate how LWFAs can be used for ultra-short time-resolved pump-probe measurements. In addition, I will discuss how, in combination with very high intensity laser beams, new physics regimes may be accessed in the future.