Experimental studies on high-energy radiation sources from laser wakefield accelerators

In this work I discuss a series of experiments on generating and characterizing a compact, ultrashort-duration source of Thomson backscatter γ-rays at the University of Texas, Austin. The γ-rays are created in a three-step process that begins with the Texas Petawatt laser-plasma accelerator producing GeV-scale electron beams. At the exit of the accelerator, the leading edge of the TPW laser pulse ionizes the surface of a glass or plastic substrate to form a plasma mirror. The plasma mirror retro-reflects a majority of the remaining laser energy back into the accelerated electrons to act as an optical undulator, which stimulates the production of γ-rays. By adjusting the separation between the plasma mirror and exit of the accelerator, we were able to simultaneously confirm that the inherently self-aligning quality of the plasma mirror is maintained over a wide range of intensities and observe the transition from linear to nonlinear Thomson backscatter. Linear Thomson backscatter calculations inferred from accelerated electron spectra imply γ-ray spectra with peaked components ranging from 5 - 85 MeV.