Transition from transparency to hole-boring in relativistic laser-solid interactions at the Texas Petawatt
type: CreativeWork
description: This dissertation examines the motion of the electron critical density surface during interactions between a relativistically intense laser pulse and a solid density target. On short time scales the laser field increases the electron quiver velocity, increasing the effective electron mass which increases the plasma frequency at a given electron density. This leads to transmission of a given laser frequency deeper into the target, known as relativistic self induced transparency with the effective critical density surface propagating quickly into the target bulk. On longer time scales, the ponderomotive force from the laser leads to large light pressure which pushes a sheet of electrons into the target bulk. This leads to a strong electric potential between the electron sheet and ions that are left behind. These ions are accelerated by the potential in a process known as hole boring. Both processes are present during laser-solid interactions, but relative contributions to critical surface motion depend on the density profile of the target and the da0/dt of the laser pulse. We have conducted experiments which use the spectral shift in second and third harmonic light generated at the target surface to measure the velocity of the laser reflection point for plastic, copper, and gold targets. This data is time integrated, with the signal limited to the period of high laser intensity. The measured second harmonic spectra show a unique two peak structure which indicates the existence of two velocity regimes in the critical surface dynamics. Qualitatively, there is a small difference between the target types. In shots on gold, the signal in the high velocity peak is slightly greater than that in the low velocity peak, and this trend is reversed for plastic targets, with copper somewhere in the middle. There is more variation in the third harmonic spectrum as spectra from gold are generally high velocity dominant, copper is transitional and show both velocity peaks, and spectr…
abstract: This dissertation examines the motion of the electron critical density surface during interactions between a relativistically intense laser pulse and a solid density target. On short time scales the laser field increases the electron quiver velocity, increasing the effective electron mass which increases the plasma frequency at a given electron density. This leads to transmission of a given laser frequency deeper into the target, known as relativistic self induced transparency with the effective critical density surface propagating quickly into the target bulk. On longer time scales, the ponderomotive force from the laser leads to large light pressure which pushes a sheet of electrons into the target bulk. This leads to a strong electric potential between the electron sheet and ions that are left behind. These ions are accelerated by the potential in a process known as hole boring. Both processes are present during laser-solid interactions, but relative contributions to critical surface motion depend on the density profile of the target and the da0/dt of the laser pulse. We have conducted experiments which use the spectral shift in second and third harmonic light generated at the target surface to measure the velocity of the laser reflection point for plastic, copper, and gold targets. This data is time integrated, with the signal limited to the period of high laser intensity. The measured second harmonic spectra show a unique two peak structure which indicates the existence of two velocity regimes in the critical surface dynamics. Qualitatively, there is a small difference between the target types. In shots on gold, the signal in the high velocity peak is slightly greater than that in the low velocity peak, and this trend is reversed for plastic targets, with copper somewhere in the middle. There is more variation in the third harmonic spectrum as spectra from gold are generally high velocity dominant, copper is transitional and show both velocity peaks, and spectr…
author: Wagner, Craig Franklin
language: en
keywords: Hole-boring, Relativistic transparency, RIT, Relativistic self induced transparency, Laser-plasma interaction, HEDP, Radiation pressure acceleration, Muon, Laser muon acceleration, Muon imaging, Target surface dynamics, Broadband laser pulse characterization, Texas Petawatt
date published: 2016-12
date modified: 2026-07-24T05:00:56Z
provider: University of Texas
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: The University of Texas at Austin

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2152/46020

PropertyValue
property ID: DOI
value: 10.15781/T27S7HZ0K