A Monte-Carlo method for coulomb collisions in hybrid plasma models

Sherlock, M.

doi:10.1016/j.jcp.2007.11.037

Cited by 37 publications

(43 citation statements)

References 18 publications

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“…There are two different types of Monte Carlo methods used to solve (3) and (5). The first is a Monte Carlo method using a drag/diffusion formulation developed by Mannheimer, Lampe, and Joyce [8] and extended recently in [12]. In their method each particle velocity evolves due to drift (drag) and random jumps (diffusion), corresponding to the drift velocity F d (or drag coefficient F d ) and the diffusion coefficient D, as in (3).…”

Section: Fokker-planck Equationmentioning

confidence: 99%

A Hybrid Method for Accelerated Simulation of Coulomb Collisions in a Plasma

Caflisch¹,

Wang²,

Dimarco³

et al. 2008

Multiscale Model. Simul.

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Abstract. If the collisional time scale for Coulomb collisions is comparable to the characteristic time scales for a plasma, then simulation of Coulomb collisions may be important for computation of kinetic plasma dynamics. This can be a computational bottleneck because of the large number of simulated particles and collisions (or phase-space resolution requirements in continuum algorithms), as well as the wide range of collision rates over the velocity distribution function. This paper considers Monte Carlo simulation of Coulomb collisions using the binary collision models of Takizuka and Abe and of Nanbu. It presents a hybrid method for accelerating the computation of Coulomb collisions. The hybrid method represents the velocity distribution function as a combination of a thermal component (a Maxwellian distribution) and a kinetic component (a set of discrete particles). Collisions between particles from the thermal component preserve the Maxwellian; collisions between particles from the kinetic component are performed using the method of Takizuka and Abe or of Nanbu. Collisions between the kinetic and thermal components are performed by sampling a particle from the thermal component and selecting a particle from the kinetic component. Particles are also transferred between the two components according to thermalization and dethermalization probabilities, which are functions of phase space. The Fokker-Planck equation has a time scale t F P , defined by the rate of change of the particle velocity vector angle. If the characteristic time t 0 of interest is large compared to t F P , then Coulomb interactions will drive the velocity distribution f (v) to its equilibrium, given by a Maxwellian distribution M , with density n M , velocity u M , and temperature T M . Further evolution of the system can be described by continuum equations for n M , u M , and T M . At the other extreme if t 0 << t F P , the plasma can be described as collisionless. In the intermediate regime with t 0 and t F P

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Section: Fokker-planck Equationmentioning

confidence: 99%

A Hybrid Method for Accelerated Simulation of Coulomb Collisions in a Plasma

Caflisch¹,

Wang²,

Dimarco³

et al. 2008

Multiscale Model. Simul.

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“…The second of these interactions is discussed in Subsection II C. Coulomb collisions are modeled using dynamic friction and diffusion coefficients in velocity-space that are a function of the particle's velocity. 24 In the simulations reported here, it is found that, in general, Coulomb collisions have only a small effect on the evolution of the computational particle momentum, which is dominated by the E and B fields. Coulomb collisions between computational particles are also modeled, but these have a very small effect due to the low density of beam ions.…”

Section: B Ion Beam Formation and Transportmentioning

confidence: 59%

Neutron spectra from beam-target reactions in dense Z-pinches

Appelbe

Chittenden

2015

Physics of Plasmas

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The energy spectrum of neutrons emitted by a range of deuterium and deuterium-tritium Z-pinch devices is investigated computationally using a hybrid kinetic-MHD model. 3D MHD simulations are used to model the implosion, stagnation, and break-up of dense plasma focus devices at currents of 70 kA, 500 kA, and 2 MA and also a 15 MA gas puff. Instabilities in the MHD simulations generate large electric and magnetic fields, which accelerate ions during the stagnation and break-up phases. A kinetic model is used to calculate the trajectories of these ions and the neutron spectra produced due to the interaction of these ions with the background plasma. It is found that these beam-target neutron spectra are sensitive to the electric and magnetic fields at stagnation resulting in significant differences in the spectra emitted by each device. Most notably, magnetization of the accelerated ions causes the beam-target spectra to be isotropic for the gas puff simulations. It is also shown that beam-target spectra can have a peak intensity located at a lower energy than the peak intensity of a thermonuclear spectrum. A number of other differences in the shapes of beam-target and thermonuclear spectra are also observed for each device. Finally, significant differences between the shapes of beam-target DD and DT neutron spectra, due to differences in the reaction cross-sections, are illustrated.

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“…Coulomb collisions between the tritons and the background plasma are modelled using a Fokker-Planck model that calculates both slowing and diffusion of the particles. [15,16] Reactions between a triton particle and the background deuterium plasma are also calculated at every time step. Given the deuterium density, temperature and the triton particle weighting, the secondary DT yield can be calculated.…”

Section: Accepted Manuscriptmentioning

confidence: 99%