Laser-driven proton beams: Mechanisms for spectral control and efficiency enhancement

Ceri Mae Brenner

Research output: ThesisDoctoral Thesis

Abstract

This thesis reports on investigations of proton acceleration driven by the interaction of short, intense laser pulses with thin, solid targets. Laser-driven plasma interactions are used to establish accelerating quasi-electrostatic field gradients, on the rear surface of the target, that are orders of magnitude higher than the current limit of conventional, radio-frequency-based accelerator technology. The resulting high energy (multi-MeV) proton beams are highly laminar, have ultra-low emittance, and the inherently broad energy spectrum is particularly effective for use in proton imaging, heating and transmutation applications. This thesis reports on a series of investigations carried out to explore routes towards control of the spectral properties of laser-driven proton sources and optimisation of laser-to-proton energy conversion efficiency. The dependence of laser accelerated proton beam properties on laser energy and focal spot size in the interaction of an intense laser pulse with an ultra-thin foil is explored at laser intensities of 1016-1018 W/cm2. The results indicate that whilst the maximum proton energy is dependent on both these laser pulse parameters, the total number of protons accelerated is primarily related to the laser pulse energy. A modification to current analytical models of the proton acceleration, to take account of lateral transport of electrons on the target rear surface, is suggested to account for the experimental findings. The thesis also reports on an investigation of optical control of laser-driven proton acceleration, in which two relativistically intense laser pulses, narrowly separated in time, are used. This novel approach is shown to deliver a significant enhancement in the coupling of laser energy to medium energy (5-30 MeV) protons, compared to single pulse irradiation. The 'double-pulse' mechanism of proton acceleration is investigated in combination with thin targets, for which refluxing of hot electrons between the target surfaces can lead to optimal conditions for coupling laser drive energy into the proton beam. A high laser-to-proton conversion efficiency is measured when the delay between the pulses is optimised at 1 ps. The subsequent effect of double-pulse drive on the angular distribution of the proton beam is also explored for thick targets.
LanguageEnglish
QualificationPhD
Awarding Institution
  • University Of Strathclyde
Supervisors/Advisors
  • Neely, David, Supervisor
  • McKenna, Paul, Supervisor
Award date17 Aug 2012
Place of PublicationGlasgow
Publisher
Publication statusPublished - 2012

Fingerprint

proton beams
augmentation
lasers
protons
pulses
theses
proton energy
energy
plasma interactions
optical control
transmutation
energy conversion efficiency
emittance
hot electrons
foils
radio frequencies
energy spectra
accelerators
angular distribution

Keywords

  • proton beams
  • spectral control
  • efficiency enhancement
  • laser-driven proton beams
  • plasma interactions

Cite this

Brenner, C. M. (2012). Laser-driven proton beams: Mechanisms for spectral control and efficiency enhancement. Glasgow: University of Strathclyde.
Brenner, Ceri Mae. / Laser-driven proton beams : Mechanisms for spectral control and efficiency enhancement. Glasgow : University of Strathclyde, 2012. 199 p.
@phdthesis{2ac0d63e071842f5908e7553c59213b4,
title = "Laser-driven proton beams: Mechanisms for spectral control and efficiency enhancement",
abstract = "This thesis reports on investigations of proton acceleration driven by the interaction of short, intense laser pulses with thin, solid targets. Laser-driven plasma interactions are used to establish accelerating quasi-electrostatic field gradients, on the rear surface of the target, that are orders of magnitude higher than the current limit of conventional, radio-frequency-based accelerator technology. The resulting high energy (multi-MeV) proton beams are highly laminar, have ultra-low emittance, and the inherently broad energy spectrum is particularly effective for use in proton imaging, heating and transmutation applications. This thesis reports on a series of investigations carried out to explore routes towards control of the spectral properties of laser-driven proton sources and optimisation of laser-to-proton energy conversion efficiency. The dependence of laser accelerated proton beam properties on laser energy and focal spot size in the interaction of an intense laser pulse with an ultra-thin foil is explored at laser intensities of 1016-1018 W/cm2. The results indicate that whilst the maximum proton energy is dependent on both these laser pulse parameters, the total number of protons accelerated is primarily related to the laser pulse energy. A modification to current analytical models of the proton acceleration, to take account of lateral transport of electrons on the target rear surface, is suggested to account for the experimental findings. The thesis also reports on an investigation of optical control of laser-driven proton acceleration, in which two relativistically intense laser pulses, narrowly separated in time, are used. This novel approach is shown to deliver a significant enhancement in the coupling of laser energy to medium energy (5-30 MeV) protons, compared to single pulse irradiation. The 'double-pulse' mechanism of proton acceleration is investigated in combination with thin targets, for which refluxing of hot electrons between the target surfaces can lead to optimal conditions for coupling laser drive energy into the proton beam. A high laser-to-proton conversion efficiency is measured when the delay between the pulses is optimised at 1 ps. The subsequent effect of double-pulse drive on the angular distribution of the proton beam is also explored for thick targets.",
keywords = "proton beams, spectral control, efficiency enhancement, laser-driven proton beams, plasma interactions",
author = "Brenner, {Ceri Mae}",
note = "EThos id: uk.bl.ethos.576339",
year = "2012",
language = "English",
publisher = "University of Strathclyde",
school = "University Of Strathclyde",

}

Brenner, CM 2012, 'Laser-driven proton beams: Mechanisms for spectral control and efficiency enhancement', PhD, University Of Strathclyde, Glasgow.

Laser-driven proton beams : Mechanisms for spectral control and efficiency enhancement. / Brenner, Ceri Mae.

Glasgow : University of Strathclyde, 2012. 199 p.

Research output: ThesisDoctoral Thesis

TY - THES

T1 - Laser-driven proton beams

T2 - Mechanisms for spectral control and efficiency enhancement

AU - Brenner, Ceri Mae

N1 - EThos id: uk.bl.ethos.576339

PY - 2012

Y1 - 2012

N2 - This thesis reports on investigations of proton acceleration driven by the interaction of short, intense laser pulses with thin, solid targets. Laser-driven plasma interactions are used to establish accelerating quasi-electrostatic field gradients, on the rear surface of the target, that are orders of magnitude higher than the current limit of conventional, radio-frequency-based accelerator technology. The resulting high energy (multi-MeV) proton beams are highly laminar, have ultra-low emittance, and the inherently broad energy spectrum is particularly effective for use in proton imaging, heating and transmutation applications. This thesis reports on a series of investigations carried out to explore routes towards control of the spectral properties of laser-driven proton sources and optimisation of laser-to-proton energy conversion efficiency. The dependence of laser accelerated proton beam properties on laser energy and focal spot size in the interaction of an intense laser pulse with an ultra-thin foil is explored at laser intensities of 1016-1018 W/cm2. The results indicate that whilst the maximum proton energy is dependent on both these laser pulse parameters, the total number of protons accelerated is primarily related to the laser pulse energy. A modification to current analytical models of the proton acceleration, to take account of lateral transport of electrons on the target rear surface, is suggested to account for the experimental findings. The thesis also reports on an investigation of optical control of laser-driven proton acceleration, in which two relativistically intense laser pulses, narrowly separated in time, are used. This novel approach is shown to deliver a significant enhancement in the coupling of laser energy to medium energy (5-30 MeV) protons, compared to single pulse irradiation. The 'double-pulse' mechanism of proton acceleration is investigated in combination with thin targets, for which refluxing of hot electrons between the target surfaces can lead to optimal conditions for coupling laser drive energy into the proton beam. A high laser-to-proton conversion efficiency is measured when the delay between the pulses is optimised at 1 ps. The subsequent effect of double-pulse drive on the angular distribution of the proton beam is also explored for thick targets.

AB - This thesis reports on investigations of proton acceleration driven by the interaction of short, intense laser pulses with thin, solid targets. Laser-driven plasma interactions are used to establish accelerating quasi-electrostatic field gradients, on the rear surface of the target, that are orders of magnitude higher than the current limit of conventional, radio-frequency-based accelerator technology. The resulting high energy (multi-MeV) proton beams are highly laminar, have ultra-low emittance, and the inherently broad energy spectrum is particularly effective for use in proton imaging, heating and transmutation applications. This thesis reports on a series of investigations carried out to explore routes towards control of the spectral properties of laser-driven proton sources and optimisation of laser-to-proton energy conversion efficiency. The dependence of laser accelerated proton beam properties on laser energy and focal spot size in the interaction of an intense laser pulse with an ultra-thin foil is explored at laser intensities of 1016-1018 W/cm2. The results indicate that whilst the maximum proton energy is dependent on both these laser pulse parameters, the total number of protons accelerated is primarily related to the laser pulse energy. A modification to current analytical models of the proton acceleration, to take account of lateral transport of electrons on the target rear surface, is suggested to account for the experimental findings. The thesis also reports on an investigation of optical control of laser-driven proton acceleration, in which two relativistically intense laser pulses, narrowly separated in time, are used. This novel approach is shown to deliver a significant enhancement in the coupling of laser energy to medium energy (5-30 MeV) protons, compared to single pulse irradiation. The 'double-pulse' mechanism of proton acceleration is investigated in combination with thin targets, for which refluxing of hot electrons between the target surfaces can lead to optimal conditions for coupling laser drive energy into the proton beam. A high laser-to-proton conversion efficiency is measured when the delay between the pulses is optimised at 1 ps. The subsequent effect of double-pulse drive on the angular distribution of the proton beam is also explored for thick targets.

KW - proton beams

KW - spectral control

KW - efficiency enhancement

KW - laser-driven proton beams

KW - plasma interactions

M3 - Doctoral Thesis

PB - University of Strathclyde

CY - Glasgow

ER -

Brenner CM. Laser-driven proton beams: Mechanisms for spectral control and efficiency enhancement. Glasgow: University of Strathclyde, 2012. 199 p.