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Ionisation effects for laser-plasma interactions by particle-in-cell code
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Lawrence-Douglas, Alistair (2013) Ionisation effects for laser-plasma interactions by particle-in-cell code. PhD thesis, University of Warwick.
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WRAP_THESIS_Lawrence-Douglas_2013.pdf - Submitted Version Download (22Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b2686775~S1
Abstract
The particle-in-cell code EPOCH was extended to include field and collisional ionisation
for use in simulating initially neutral or partially-ionised targets in laser-plasma inter-
actions. The means by which particles ionise in the the field of an intense laser was
described and physical models were included to determine the instantaneous ionisa-
tion rate at particles within the simulation domain for multiphoton, tunnelling, barrier-
suppression and electron-impact ionisation. The algorithms used to implement these
models were presented and demonstrated to produce the correct ionisation statistics. A
scheme allowing for modelling small amounts of ionisation for an arbitrarily low number
of superparticles was also presented for comparison and it was shown that for sufficient
simulation time the two schemes converge. The three major mechanisms of ionisation
in laser-plasma interactions were described as being ionisation-induced defocussing, fast
shuttering and ionisation injection. Simulations for these three effects were presented
and shown to be in good agreement with theory and experiment. For fast-shuttering,
plasma mirrors were simulated using the pulse profile for the Astra Gemini laser at the
Central Laser Facility. Rapid switch-on and the theoretical maximum for contrast ratio
was observed. For ionisation injection, simulations for laser wakefield acceleration in a
helium gas were performed and the accelerated electron population was shown to be
greatly increased through use of a 1% nitrogen dopant consistent with the experimental
results of McGuffey et al. A study of the laser filamentation instability due to SRS
backscatter at the relativistically corrected quarter critical surface (RCQCS) was per-
formed in collaboration with C.S. Brady and T.D. Arber at the University of Warwick
[1]. It was found that for hydrogen and plastic the instability was unaffected by the in-
clusion of ionisation. Further study with argon revealed a
attening of the RCQCS and
it was demonstrated that for a material with multiple ionisation levels ionising strongly
near the self-focussed intensities at the RCQCS, rapid ionisation caused an inversion of
the RCQCS that suppressed the filamentation instability.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QA Mathematics Q Science > QC Physics |
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Library of Congress Subject Headings (LCSH): | Ionization, Laser-plasma interactions, Ionization -- Mathematical models | ||||
Official Date: | April 2013 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Physics | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Arber, T. D. | ||||
Sponsors: | Engineering and Physical Sciences Research Council (EPSRC) | ||||
Extent: | x, 149 leaves : illustrations. | ||||
Language: | eng |
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