Laser plasma accelerator and wiggler
Author(s)
Kneip, Stefan
Type
Thesis
Abstract
This thesis details experimental research of laser-driven electron acceleration from
underdense plasmas and the characterisation of the x-ray radiation owing to the
transverse oscillatory motion that electrons perform during the acceleration process.
Acceleration of monoenergetic electron beams to the GeV level was achieved for
the first time in a self-guiding, self-injecting wakefield accelerator in the nonlinear
regime, driven by the 200 TW Astra Gemini laser. The laser pulse was shown to
be self-guided for 1 cm or more than ten times its Rayleigh range, by measurement
of a single filament containing > 30% of the initial laser energy at this distance. The
intensity in the guided filament is amplified beyond its initial value, as suggested by
the GeV electron energy gain. Three dimensional numerical modeling is in excellent
agreement with the experimental findings.
In this regime, a beam of tens of keV x-rays emanating from a micrometer source
with milliradian divergence, spatial coherence and a peak brightness comparable to
third generation light sources was measured on experiments with the 100 TW Hercules
laser. The measurements show that, due to their small transverse oscillations,
the electron trajectories and their radiation properties resemble the scenario of an
electron in a wiggler-type insertion device, with a strength parameter K close to
1. The experimental findings are supported by three dimensional modeling of the
electron and x-ray beam.
Betatron radiation was also measured with ten times longer and more intense
pulses from the Vulcan Petawatt laser. In this case, electron acceleration is
strongly driven transversely by the laser and a betatron resonance leads to a tenfold
increase in oscillation amplitude. This alters the characteristics of the emitted
synchrotron radiation fundamentally, increasing 50-fold the strength parameter and
divergence, 10-fold the source size and up to 5-fold the x-ray energy, thereby broadening
the electron energy distribution and converting up to 5% of their energy into
x-rays.
The studies provide evidence for the scalability of self-guided laser wakefield
accelerators from 0.1 to 1 GeV. Furthermore the work demonstrates that betatron
radiation can help to understand the acceleration process and has characteristics
comparable to conventional synchrotron light.
underdense plasmas and the characterisation of the x-ray radiation owing to the
transverse oscillatory motion that electrons perform during the acceleration process.
Acceleration of monoenergetic electron beams to the GeV level was achieved for
the first time in a self-guiding, self-injecting wakefield accelerator in the nonlinear
regime, driven by the 200 TW Astra Gemini laser. The laser pulse was shown to
be self-guided for 1 cm or more than ten times its Rayleigh range, by measurement
of a single filament containing > 30% of the initial laser energy at this distance. The
intensity in the guided filament is amplified beyond its initial value, as suggested by
the GeV electron energy gain. Three dimensional numerical modeling is in excellent
agreement with the experimental findings.
In this regime, a beam of tens of keV x-rays emanating from a micrometer source
with milliradian divergence, spatial coherence and a peak brightness comparable to
third generation light sources was measured on experiments with the 100 TW Hercules
laser. The measurements show that, due to their small transverse oscillations,
the electron trajectories and their radiation properties resemble the scenario of an
electron in a wiggler-type insertion device, with a strength parameter K close to
1. The experimental findings are supported by three dimensional modeling of the
electron and x-ray beam.
Betatron radiation was also measured with ten times longer and more intense
pulses from the Vulcan Petawatt laser. In this case, electron acceleration is
strongly driven transversely by the laser and a betatron resonance leads to a tenfold
increase in oscillation amplitude. This alters the characteristics of the emitted
synchrotron radiation fundamentally, increasing 50-fold the strength parameter and
divergence, 10-fold the source size and up to 5-fold the x-ray energy, thereby broadening
the electron energy distribution and converting up to 5% of their energy into
x-rays.
The studies provide evidence for the scalability of self-guided laser wakefield
accelerators from 0.1 to 1 GeV. Furthermore the work demonstrates that betatron
radiation can help to understand the acceleration process and has characteristics
comparable to conventional synchrotron light.
Date Issued
2010-03
Date Awarded
2010-06
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Najmudin, Zulfikar
Creator
Kneip, Stefan
Publisher Department
Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)