EXPERIMENTAL STUDY OF LASER PRODUCED ELECTRON BEAM

In this thesis, experimental studies are presented on longitudinal space-charge wave dynamics in space-charge dominated beams. Space-charge wave equations are derived using a cold-fluid model. Two kinds of perturbation are examined: an initial single peak pure-density perturbation and a small sinusoidal density modulation. The theoretical evolution of these two kinds of perturbation is compared with WARP RZ simulations. A new experimental method using a laser to produce such an initial pure-density perturbation is studied. The propagation of the resulting space-charge waves in University of Maryland Electron Ring (UMER) is measured and analyzed for different combinations of main beam current and perturbation current. Good agreement is achieved in all the theoretical analyses, simulation results and experimental measurements. In addition to the longitudinal space-charge wave dynamics study, the reconstruction of the transverse phase space of the photoemission beam is also reported

Efficiency Enhancement of Gallium Arsenide Photovoltaics Using Solution-Processed Zinc Oxide Nanoparticle Light Scattering Layers

We demonstrate a high-throughput, solution-based process for subwavelength surface texturing of a III-V compound solar cell. A zinc oxide (ZnO) nanoparticle ink is spray-coated directly on top of a gallium arsenide (GaAs) solar cell. The nanostructured ZnO films have demonstrated antireflection and light scattering properties over the visible/near-infrared (NIR) spectrum. The results show a broadband spectral enhancement of the solar cell external quantum efficiency (EQE), a 16% enhancement of short circuit current, and a 10% increase in photovoltaic efficiency