CER SEMINAR

Ultra intense laser ion acceleration and contrast-enhancing plasma mirrors – experiment and simulations

Ginevra Cochran, Ohio State University
April 19, 2018, 11:00am - 12:00pm, SERF Room 232

ABSTRACT:

The interplay between different laser ion acceleration mechanisms can be studied by varying parameters such as target thickness and laser angle of incidence. These experiments often require high pulse temporal contrast in order to minimize modification of the target surface by pre-pulse. We have recently demonstrated liquid crystal films as effective plasma mirrors for pulse cleaning. Presented here are novel LSP particle-in-cell simulations of plasma mirror operation that start with a cold, dense, neutral dielectric substrate and achieve excellent agreement with experiment over 3 decades in peak intensity. Data from an ion acceleration thickness scan using liquid crystal targets over target thicknesses ranging from 6 nm to > 1 µm is presented next, conducted at 45 degrees angle of incidence at an intensity of 1021 W/cm2. The ions produced were predominantly directed along the target normal for all thicknesses, with peak proton energies up to 26 MeV. Particle-in-cell simulations will be discussed which reproduce the experimental results. Particle tracking analysis reveals that as target thickness decreases, the origin of dominant high energy ions shifts from the rear target surface to volumetric behavior, with the highest energy ions originating at the target front surface. The ion acceleration mechanism evolves, while always yielding primarily near-target normal ions. The deformation of the target is well modeled using a momentum argument.

This work is supported by the AFOSR under award FA9550-14-1-0085, by the NNSA under DE-NA0003107, and by an allocation of computing time from the Ohio Supercomputer Center.

BIO:

Ginevra Cochran is a graduate student at The Ohio State University, studying high energy density physics under Douglass Schumacher. Her work focuses on ultrashort intense laser-matter interactions, in particular thin target ion acceleration and the physics of contrast-enhancing plasma mirrors, through a joint experimental-simulation approach.