On the Origin of Super-Hot Electrons in Intense Laser-Plasma Interactions

This thesis investigates the ultraintense laser-plasma interaction. An experiment to measure the generation of relativistic electrons and positrons was performed at the Texas Petawatt laser which resulted in the observation of the highest known positron energies ever recorded. The positrons are created by the Bethe-Heitler process where an electron scatters and emits bremsstrahlung radiation which then interacts with an atomic nucleus and creates an electron-positron pair. The positron bunch is a useful diagnostic for understanding the laser-plasma interaction. Modeling results are also presented that describe the acceleration mechanism for the highest energy electrons which drive many important applications. A simple mechanism we call loop-injected direct acceleration that is found to be overwhelmingly dominant in the acceleration of super-hot electrons is discussed in detail.