The state-of-the-art X-ray source based on inverse-Compton scattering between a high-brightness, relativistic electron beam produced by an X-band RF accelerator and a high-intensity laser pulse generated by chirped-pulse amplification (CPA) has been carried out by our research team at Lawrence Livermore National Laboratory. This system is called "Compact Laser-Compton X-ray Source". The applications include nuclear resonance fluorescence, medical imaging and therapy, and nuclear waste imaging and assay. One of the key factors in this system is how we know the interaction happened in the vacuum chamber, which is the spectrometer of electron beams. The other key factor is the interaction after the spectrometer, which is the outgoing X-ray. In this thesis, the work in the simulation for the result of the interaction between electrons and the laser, the calibration of spectrometer, and laser focus characterization are discussed.

Neutronics study to determine the validity and real world extendibility through Artificial Intelligence (AI) optimization of a transmutation concept with the aim of significantly reducing the radiotoxicity of Spent Nuclear Fuel (SNF) together with its required storage duration and volume. In this transmutation concept (the transmutator) utilizes a novel source providing laser-generated neutrons to transmute transuranic elements separated from SNF and dissolved in a molten salt within a subcritical core. The source neutrons are generated via beam-target fusion whereas the beam is created by laser irradiation of nanometric foils through the Coherent Acceleration of Ions by Laser (CAIL) process. This relatively low deuteron energy is catapulted by fusion and eventually by secondary fission processes. A significant factor in this study is that this can be accomplished using relatively cheap fiber lasers terminating onto small scale targets. Consequently, this makes possible the use of multiple tunable and distributable neutron sources. Such a source has not previously been considered and encourages an investigation with the aid of AI into new spatial arrangement and temporal control operation strategies as done here. This source is combined with a molten salt core whose liquid state allows and facilitates homogeneity by mixing, safety, laser irradiation, in-situ processing, and monitoring of chemical and physical properties. The combined use of molten salt and laser also allows for the introduction of rapid feedback or feedforward control of the system’s operation. This further extends the transmutator concept as this work demonstrates here by neutronics simulations showing: Efficient and continuous Minor Actinide (MA) waste only burning through AI optimized and balanced processing scheduling without the use of isotopic separation. As well as shaped thermal reactivity insertion for increased tank usage efficiency and active thermal management.

Recent developments in ultrashort (~ 30-50 fs) laser technology such as chirped pulse amplification (CPA) have made relativistic laser-plasma interactions accessible to research institutions and universities across the globe and paved the way for research institutions to increase laser pulse power beyond 1 petawatt. The high achievable intensities and ultrashort pulse durations now available have reinvigorated the fields of nonlinear optics and photonics as well as high intensity laser-plasma physics. Theoretical models which could previously only be explored computationally such as laser wakefield acceleration are now routinely realized experimentally and are being perfected at labs across the globe.

Though much progress has been made, there is a nearly accessible regime that could open the door to a new class of laser-plasma interactions providing novel schemes for heavy particle acceleration and secondary coherent source generation, the single-cycle regime. High efficiency pulse compression schemes such as thin film compression (TFC) have made possible the increase in optical power through a decrease in pulse duration. This technique not only serves as a powerful shortcut to higher laser peak power, but also reduces the laser pulse duration-consequently increasing the degree of coherence of the interactions of compressed laser pulses with plasmas.

The first half of this thesis is dedicated to demonstrating this pulse compression at intensities comparable to petawatt facilities (~ 1 TW/cm^2). Pulse compression experiments were carried out in the Dollar Lab at UCI, the LASERIX facility at the Universite Paris-Sud and the HERCULES laser at the University of Michigan. Pulse compression of a factor of ~2 has been demonstrated on multiple laser systems using fused silica as the nonlinear medium, with slightly better compression using plastics. Furthermore, laser mode quality is seen to be largely maintained in the process of nonlinear spectral broadening (which is required for pulse compression) in the highest power systems. Finally, a set of preliminary studies at near-infrared wavelengths (1140 - 1500 nm) investigate the high intensity spectral broadening in various dispersion regimes motivated by the potential for self-compression.

In the second half of this thesis particle-in-cell simulations are carried out that utilize x-ray laser pulses which could be generated by a combination of TFC and laser-plasma interactions in the single-cycle regime to drive laser wakefields in nanotubes. The laser wakefields generated in these nanotubes are shown to drive unprecedented acceleration gradients of up to TeV/cm and also an increased laser pulse propagation and therefore laser wakefield lifetime. At the other density extreme, another particle-in-cell study was performed investigating the possibility of laser wakefields as a contributing acceleration mechanism for ultra-high energy cosmic rays from blazar jets. In each case, the particle acceleration and photon emission properties of the wakefield are analyzed and scaling laws are developed for various parameters of interest, and are compared and contrasted to typical laboratory cases.