UC Berkeley

This thesis presents progress on a demonstration experiment of two-color ionization injection (TCII) in laser driven plasma accelerators (LPAs). The method has been theorized to potentially produce ultra-low, tens of nm rad, emittance beams, but has yet to be demonstrated in the laboratory. Were LPAs to reliably produce ultra-low emittance beams, they would become compact sources for a number of applications that require high brightness beams enabled by low emittance.Circularly polarized drive pulses were used for the first time to turn off ionization injection and prepare a dark-current-free wake for further injection. A regime was found in which wakes generated by circularly polarized pulses were proven to be of equivalent amplitude as those generated by linearly polarized pulses, but unlike the linearly polarized case, ionized electrons were not injected into the trapped region of the wake.High intensity, broadband, ultrashort third harmonic pulses were generated for ionization injection of electrons into a preformed wakefield accelerator for the first time. A low ponderomotive potential but high electric field injector was formed by harmonic conversion of 800 nm fundamental wavelength to 267 nm. Harmonic conversion efficiency as a function of intensity, bandwidth, and crystal thicknesses were measured. A UV pulse diagnostic was built to resolve pulse length and higher order nonlinearities.Planar laser-induced fluorescence (PLIF) was used to customize LPA targets for the first time. PLIF, combined with fluid simulations, were used to iteratively design gas density profiles for desired features. Manufactured nozzles were subsequently qualified via PLIF.Finally, methods of spatial and temporal coupling of the third harmonic injector into the preformed wake are presented and show achievement of femtosecond and micrometer precision required for controlled injection of low emittance beams.