Thesis

Experimental study of laser-driven electron and proton acceleration

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Awarding institution
  • University of Strathclyde
Date of award
  • 2012
Thesis identifier
  • T13311
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Department, School or Faculty
Abstract
  • This thesis addresses two important topics in the field of laser-driven plasma accelerators. Firstly, the research investigates the generation of relativistic electron beams through laser-wakefield acceleration (LWFA) by applying novel tapered capillary discharge waveguide accelerators, produced by femtosecond laser micromachining. A stable plasma waveguide is formed in a hydrogen-filled capillary driven by an all-solid state high-voltage pulser, specially constructed for this purpose. A longitudinal density taper has been confirmed by measurement of the transverse plasma density profiles at both ends of the waveguide and efficient guiding of low intensity (~10¹² W/cm²), ultra-short duration (50 fs) laser pulses is demonstrated. For optimal high-power laser conditions (intensity of 1.6 x 10¹⁸ W/cm²), electron beams are produced and compared in positively tapered, negatively tapered and straight capillaries with similar plasma densities of 3-6 x 10¹⁸ cm-3 over a length of 4 cm. In all three capillaries, low charge (<3 pC), low divergence (<4 mrad) monoenergetic electron beams are produced with resolution-limited energy spreads down to 1%. Significantly, an energy enhancement of 22% is obtained in the positive tapered capillary to obtain bunch energies up to 290 MeV, which may arise from the density taper. In addition, the negatively tapered capillary gives the best shot-to-shot pointing stability of the electron beam (mean r.m.s. fluctuation of 1.7 mrad). Secondly, enhanced yields of protons and ions from laser interactions with solid targets have been investigated. Using a second high power laser system (intensity of ~4 x 10¹⁹ W/cm²), hydrogen-doped foils of Au, Cu and Ti have been used as targets to identify the effect of hydrogen implantation on the produced proton beam. From these novel experiments, it has been demonstrated that an enhancement in the proton yield by approximately a factor of 3 is obtained from hydride Au and Cu targets for proton energies of ~3 MeV.
Resource Type
DOI
Date Created
  • 2012
Former identifier
  • 966981

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