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In modeling the charged alpha particle transport in hot-spot plasmas of inertial confinement fusion, the energy-losing rate is a major concern in the Monte Carlo simulations of alpha particle transport of a radiative-hydrodynamic code. However, the traditionally used energy stopping-power only describes the averaged energy-losing rate of the incident charged particles, whereas the variance of the energy exchange with the background particles is generally ignored. In this paper, the variance of charged particle collisions is studied by both analytical derivation and Monte Carlo simulations. An expression of the divergence of the charged particle energy-losing rate is given for the first time, which can be directly used for practical estimations. It indicates that when the areal density of the target particles along the incident particle path length is low, the divergence of the lost energy would be much larger than the average value, and the traditionally used energy stopping-power would be no longer sufficient to describe the charged particle Coulomb collisions. It helps to obtain a more comprehensive understanding about the charged particle transport in plasmas. [ABSTRACT FROM AUTHOR]

In the alpha particle transport in ICF hotspot, previous models focus mainly on how the incident particles lose their energy but lost sight of how the target particles will respond to this lost energy. In this paper, we developed a novel single-scattering model based on the Monte Carlo method, which abandons the stopping-power and models every single-scattering event in the alpha particle life. It enables to describe both the energy stopping of the incident alpha particle and the target particles response to the collisions. With this model, it shows that the target DT-ions at the ICF hotspot boundary will be non-Maxwellian distributed after colliding with the high-energy alpha particles, which refers to a much higher fusion reactivity compared with a Maxwellian one. At the same time, this model gives a longer and dispersed alpha particle range in hotspot plasmas and suggests that the traditionally used stopping power models would overestimate the stopping ability of the target particles. [ABSTRACT FROM AUTHOR]