CER SEMINAR

High-Intensity Laser Acceleration of Electrons at Normal Incidence

Joshua May Institute of Laser Engineering, Osaka University
February 1, 2018, 2:00pm - 3:00pm, SERF Room 232

ABSTRACT:

The interaction of high intensity linearly-polarized lasers (eA/mec ≡ a0 >> 1) with solid-density matter at normal incidence is a fundamental question. We show that, while the surface remains smooth and sharp, the laser energy is absorbed by hot electrons interacting with the standing wave structure of the partially reflected wave at the plasma surface; initially cold targets absorb due to heating at the surface caused by unstable electron flows in the evanescent fields. This mechanism accelerates electrons to proper velocities of twice the laser vacuum quiver velocity; conservation of transverse canonical momentum means that all electrons enter the plasma with non-zero velocity in the direction of the laser electric field. When the surface is no longer smooth or sharp, electrons are able to escape the surface and gain energy through stochastic motion in the superimposed incoming and reflected waves, leading to peak momenta without theoretical limit. Surface acceleration still occurs as well, and total absorption is governed by the competition between these mechanisms. We also show how the mechanism for acceleration at the surface explains the need for circular polarization in Radiation Pressure Acceleration of ions. 

BIO:

Joshua May is currently a researcher at UC Los Angeles. He received a PhD from UCLA in 2017, with a dissertation titled, "On the Acceleration and Transport of Electrons Generated by Intense Laser-Plasma Interactions at Sharp Interfaces;" before that he received a BA in Mathematics with honors and a BS in Physics with highest honors from UC Santa Cruz. His research focuses on kinetic plasma physics, especially in high energy-density and relativistic systems.