Laser Driven Electron and X-ray Sources Based on Micro-structured Targets

Laser generated electrons play a crucial role in laser plasma interactions. These fast electrons mediate the transfer of laser energy to the target and drive subsequent processes such as ion acceleration and Bremsstrahlung radiation. To date, most of laser-solid target interaction research has been focused on flat interfaces. In this thesis, a novel approach to laser plasma interactions is proposed. It takes advantage of recent advances in nano-technology and laser pulse cleaning techniques to achieve intense electron beams. The proposed targets consist of highly aligned front-surface target structures. Using three-dimensional Particle-In-Cell (PIC) simulations, the mechanism of electron production and acceleration in micro-wire arrays is investigated. It is found that electrons are accelerated via the direct laser acceleration mechanism and are guided by the strong quasi-static plasma fields near the structure surface. First experimental evidence of electron enhancement using these novel targets is carried out on the Scarlet laser facility at a laser intensity of 10 21 W/cm2. These proof of principle experiments show the maximum electron energy is 70 MeV with structured targets compared to 20 MeV with flat interface. An optimum target geometry that produces high-energy electrons well above 100 MeV while confining the emission to narrow (< 5 deg) is proposed at 5 x 1021 W/cm2. Furthermore, Monte Carlo simulations show that with a secondary high-Z converter target, these electrons can produce bright Bremsstrahlung radiation. The peak gamma ray brightness for this source is 6.0 x 1019 s--1 mm --2 mrad--2 at 10MeV and 1.4 x 1019 s--1 mm--2 mrad --2 at 100MeV (0.1% bandwidth). The combination of laser plasma physics and nano-technology not only makes it possible to control the rather stochastic nature of laser-plasma interaction but also opens up a new field of research with great promise.