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Spreading of collimated particle beams within a generalized Fokker-Planck diffusion equation

Robert Nyqvist (Institutionen för radio- och rymdvetenskap, Icke-linjär elektrodynamik) ; Dan Anderson (Institutionen för radio- och rymdvetenskap, Icke-linjär elektrodynamik) ; Mietek Lisak (Institutionen för radio- och rymdvetenskap, Icke-linjär elektrodynamik)
Nuclear Science and Engineering (0029-5639). Vol. 163 (2009), 1, p. 85-90.
[Artikel, refereegranskad vetenskaplig]

Recently, an expansion of the Boltzmann scattering operator describing the angular spreading of particle beams was given that included the effects of large angle scattering processes, thus generalizing the classical Fokker-Planck equation, valid in the limit of small angle scattering. The present work aims at making an analytical comparison between predictions based on the classical Fokker-Planck equation and those based on a generalized one, which includes a first-order correction term in the expansion of the Boltzmann scattering operator. The analysis is carried out for thin slabs where backscattering effects can be neglected and makes use of a moment approach, which leads to an infinite system of recursively coupled ordinary differential equations. The system is truncated in a consistent manner, and the effects of large angle scattering on the evolution of the moments are determined in explicit analytical form. An approximate similarity solution of the generalized Fokker-Planck equation is also found, and the results of both approaches provide a clear picture of the increased diffusive beam spreading due to large angle scattering. A comparison with previously published Monte Carlo simulation results shows good agreement.



Denna post skapades 2009-09-24. Senast ändrad 2014-09-02.
CPL Pubid: 98670

 

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Institutioner (Chalmers)

Institutionen för radio- och rymdvetenskap, Icke-linjär elektrodynamik (2005-2010)

Ämnesområden

Fusion, plasma och rymdfysik

Chalmers infrastruktur