Nicholas P. Ernst PhD Dissertation Defense: “Tailored spatio-temporal control of high-intensity lasers for applications to next generation particle accelerators”

Abstract:

Entering the stages of a mature technology, laser-driven particle accelerators now look toward utilizing advanced techniques for improving radiation yield, beam quality, stability, and repetition-rate. Employing the influence of complex or “structured” light provides one such method to do so. In general, modifications to the electric field distribution on target can be approached using two methods: 1) spatio-spectral shaping of an individual pulse, 2) co-incident multi-laser interactions. This dissertation includes experiments, modeling, and discussion of both concepts. To begin, the role and manipulation of a known low-order spatio-temporal coupling, pulse-front curvature (PFC), is explored on the 3 PW Zettawatt-Equivalent Ultrashort pulse laser System (ZEUS). Work here includes compensating the curvature during laser amplification through careful optical design, a novel metrology technique which extends the use of a single-shot autocorrelator (the GRENOUILLE), design of specialty zero-power chromatic
doublets to produce the coupling, and preliminary experiments to identify the role of this coupling in laser wakefield acceleration (LWFA) by generation of chromatic flying-foci. Further, it is shown the use of two or more high-intensity laser pulses can be co-propagated in an underdense plasma to provide tunable electron injection by creating an ad hoc spatio-temporal distortion. Taking advantage of the non-linear plasma response, pulse coupling leads to predictable, asymmetric plasma wave shaping that can produce mono-energetic electron beams, high-radiation betatron sources, and/or pulse steering. Finally, the concept is extended to a large or “infinite” array of co-propagating lasers. A simple approach to modeling this multi-laser interaction is presented and applied to both electron acceleration from LWFA and ion acceleration from target-normal sheath acceleration (TNSA). Particle-in-cell simulations show laser cross-talk, energy exchange, interference, and coherent plasma wake excitation can  unlock a new regime of wakefield acceleration for a spatially extended, high-brilliance electron synchrotron and bremsstrahlung radiation source. These multi-pulse methods would be well suited for emerging fiber-laser architectures and may pave a route towards the next generation of controlled, compact, portable, high-repetition laser driven accelerators.

Dissertation Committee:
Karl M. Krushelnick, Chair
Alexander G.R. Thomas
Louise Willingale
Milos Burger
Paul T. Campbell