https://doi.org/10.1140/epjd/s10053-025-00951-w
Regular Article - Plasma Physics
Space-resolved transport properties of the thermalizing particle ensemble via Monte Carlo simulations
Institute of Physics, University of Belgrade, POB 68, 11080, Belgrade, Serbia
Received:
19
October
2024
Accepted:
22
December
2024
Published online:
24
January
2025
Understanding the thermalization process of mono-energetic particle beams in gases is fundamental for various applications in plasma physics. A statistical model is introduced and analyzed through Monte Carlo simulations. The simulations are initialized with a delta-function impulse of a non-interacting particle beam colliding with a gas in an infinite domain at a finite temperature. Spatially-resolved profiles of the thermalizing particles, including their average kinetic energy, reveal spatial variations during their evolution. The overall energy balance over time reveals that the local kinetic energy near the center of mass of the thermalizing particles is lower than the thermal energy of the gas, a phenomenon referred to as ‘diffusive cooling’. At the periphery of the particle swarm, the local kinetic energy exceeds the thermal energy, resulting in ‘diffusive heating’. Previous studies have mostly examined these phenomena separately and in confined spaces, such as those observed in the Cavalleri experiment. These effects are explored in an unbounded gas. Calculated quasi-stationary, spatially-resolved profiles in an unbounded gas are compared with stationary profiles observed in confined systems between two infinite planes with perfect absorption. The effective diffusion coefficient, derived from the diffusion equation used in the Cavalleri model, is shown to align with the flux value of the transverse diffusion coefficient predicted by swarm theory. Additionally, it was observed that certain thermalized particles exhibit higher kinetic energy than their initial values at both the front and tail edges of the beam, marking an unexpected transitional phenomenon in the evolution of the beam swarm.
Key words: Monte Carlo simulation / Thermalization / Swarm / Spatiotemporal development / Diffusion cooling and heating
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1140/epjd/s10053-025-00951-w.
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Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.
