With the advent of petawatt-class laser facilities, laser intensities reach unprecedented levels enabling novel and efficient regimes of secondary particle and radiation beams. A regime involving relativistic transparency of dense plasmas and the generation of a Megatesla-level azimuthal magnetic field is shown to be promising for generating energetic electrons and collimated gamma-ray beams. This dissertation focuses on the above regime to explore the acceleration mechanism of electrons, to optimize the gamma-ray yield, to examine the application to two-photon pair production, and to investigate the feasibility of magnetic field detection.
First, we investigate direct laser acceleration in the presence of a strong azimuthal magnetic field. Test-particle models are built to explain the enhanced acceleration. The magnetic fields mitigate electron dephasing and allow an efficient acceleration over a short distance. We then report the important role of the laser phase velocity on electron confinement in this acceleration regime.
We investigate the emission of collimated gamma-ray beams from laser-irradiated channel targets through three-dimensional kinetic simulations. We find a strong power scaling of conversion efficiency into MeV-level photons. The electron-positron pair production via two-photon collisions directly benefits from such a power scaling. We explore two schemes of generating pairs through the linear Breit-Wheeler process: colliding two gamma-ray beams and colliding one gamma-ray beam with blackbody radiation. The strong power scaling boosts the pair yield to the level of 100,000.
Our research on the hollow-channel regime corroborates the robustness of prefilled channels. Due to the influence of ion motion, electrons acceleration and photon emission degrade in hollow channels. With a broader angular spread of gamma-ray beams, the pair yield in hollow channels is shown to be less efficient.
At last, we examine the feasibility of detecting Megatesla-level magnetic fields. We choose XFEL beams to detect magnetic fields, based on the magnetic field inducing a polarization rotation via the Faraday effect. A setup of structured targets with a prefilled channel which mitigates the reduction of rotation caused by relativistic transparency is necessary to achieve rotations that exceed 0.1 mrad. A study on laser focusing configurations suggests there is flexibility regarding laser intensities.
|Commitee:||Beg, Farhat, Quest, Kevin, Surko, Clifford, Tynan, George|
|School:||University of California, San Diego|
|Department:||Mechanical and Aerospace Engineering|
|School Location:||United States -- California|
|Source:||DAI-B 82/1(E), Dissertation Abstracts International|
|Subjects:||Plasma physics, Physics|
|Keywords:||Direct laser accelelration, High-power lasers, Laser plasma interaction, Mega-tesla magnetic fields, Particle-in-Cell simulations, Relativistic transparency|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be