Generation and transport of high-current relativistic electron beams in high intensity laser-solid interactions

Mireille Coury

Research output: ThesisDoctoral Thesis

Abstract

In this thesis, the generation and transport of ultra-high intensity laser-driven relativistic electron beams in overdense plasma is investigated experimentally and numerically. The fast electron beam is experimentally diagnosed by means of a 2D Cu Kα imager and the TNSA-generated proton beam. Analytical models together with a 3D hybrid-PIC code are employed to simulate the beam properties in solids. The effects of the self-generated fields on the fast electron beam transport, the effect of the preplasma density scale length on the laser energy coupling to fast electrons and the influence of the laser spot size on the fast electron beam generation and transport, and on the subsequent proton beam, are reported.

Fast electron injection and transport in metal foils irradiated at laser intensity up to 4 × 1020 W/cm2 , is investigated . The beam transport is simulated over a wide range of beam source conditions and with or without inclusion of selfgenerated magnetic fields. The resulting hot electron beam properties are used in rear-surface plasma expansion calculations to compare with measurements of the beam of accelerated protons. An injection half-angle of ∼ 50◦ − 70◦ is inferred, which is larger than that derived from previous experiments under similar conditions.

The influence of laser spot size on laser energy coupling to electrons, and subsequently to the TNSA-generated protons, in foil targets is reported. Proton acceleration is characterized for laser intensities ranging from 2 × 1018 - 6 × 1020 W/cm2 , by variation of the laser energy for a fixed spot size, and by variation of the spot size for a fixed energy. At a given laser pulse intensity, the maximum proton energy is higher under defocus illumination compared to tight focus. The results are explained in terms of higher laser pulse energy and geometrical changes to the hot electron injection.

The laser-to-electron energy conversion efficiency is investigated in metal foils over a wide range of preplasma density scale lengths. A hybrid-PIC code is employed to model the fast electron beam transport in the solid, for a given hot electron source. The resulting fast electron density is used to infer the maximum proton energy for comparison with experimental results. It is shown, in agreement with previous published work, that some preplasma density scale length leads to an enhancement of the energy coupling efficiency of laser light to fast electrons.
Original languageEnglish
QualificationPhD
Awarding Institution
  • University Of Strathclyde
Supervisors/Advisors
  • McKenna, Paul, Supervisor
Place of PublicationGlasgow
Publisher
Publication statusPublished - 30 May 2013

Keywords

  • electron beams
  • high intensity laser-solid interactions
  • overdense plasma

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