We describe the development of a 3D Monte-Carlo model to study hot-electron transport in ionized or partially ionized targets,considering regimes typical of inertial confinement fusion.Electron collisions are modeled ...We describe the development of a 3D Monte-Carlo model to study hot-electron transport in ionized or partially ionized targets,considering regimes typical of inertial confinement fusion.Electron collisions are modeled using a mixed simulation algorithm that considers both soft and hard scattering phenomena.Soft collisions are modeled according to multiple-scattering theories,i.e.,considering the global effects of the scattering centers on the primary particle.Hard collisions are simulated by considering a two-body interaction between an electron and a plasma particle.Appropriate differential cross sections are adopted to correctly model scattering in ionized or partially ionized targets.In particular,an analytical form of the differential cross section that describes a collision between an electron and the nucleus of a partially ionized atom in a plasma is proposed.The loss of energy is treated according to the continuous slowing down approximation in a plasma stopping power theory.Validation against Geant4 is presented.The code will be implemented as a module in 3D hydrodynamic codes,providing a basis for the development of robust shock ignition schemes and allowing more precise interpretations of current experiments in planar or spherical geometries.展开更多
We describe two numerical investigations performed using a 3D plasma Monte-Carlo code,developed to study hot-electron transport in the context of inertial confinement fusion.The code simulates the propagation of hot e...We describe two numerical investigations performed using a 3D plasma Monte-Carlo code,developed to study hot-electron transport in the context of inertial confinement fusion.The code simulates the propagation of hot electrons in ionized targets,using appropriate scattering differential cross sections with free plasma electrons and ionized or partially ionized atoms.In this paper,we show that a target in the plasma state stops and diffuses electrons more effectively than a cold target(i.e.,a target under standard conditions in which ionization is absent).This is related to the fact that in a plasma,the nuclear potential of plasma nuclei has a greater range than in the cold case,where the screening distance is determined by the electronic structure of atoms.However,in the ablation zone created by laser interaction,electrons undergo less severe scattering,counterbalancing the enhanced diffusion that occurs in the bulk.We also show that hard collisions,i.e.,collisions with large polar scattering angle,play a primary role in electron beam diffusion and should not be neglected.An application of the plasma MonteCarlo model to typical shock ignition implosions suggests that hot electrons will not give rise to any preheating concerns if their Maxwellian temperature is lower than 25–30 keV,although the presence of populations at higher temperatures must be suppressed.This result does not depend strongly on the initial angular divergence of the electron beam set in the simulations.展开更多
基金This work has been carried out within the framework of the EUROfusion Enabling Research Project No.AWP17-ENR-IFECEA-01“Preparation and Realization of European Shock Ignition Experiments”and has received funding from the Euratom Research and Training Program 2014-2018 under Grant Agreement No.633053The views and opinions expressed herein do not necessarily reflect those of the European Commission.The authors thank Professors Vladimir Tikhonchuk and Stefano Atzeni for many useful discussions.We also thank the anonymous reviewers for their constructive comments.
文摘We describe the development of a 3D Monte-Carlo model to study hot-electron transport in ionized or partially ionized targets,considering regimes typical of inertial confinement fusion.Electron collisions are modeled using a mixed simulation algorithm that considers both soft and hard scattering phenomena.Soft collisions are modeled according to multiple-scattering theories,i.e.,considering the global effects of the scattering centers on the primary particle.Hard collisions are simulated by considering a two-body interaction between an electron and a plasma particle.Appropriate differential cross sections are adopted to correctly model scattering in ionized or partially ionized targets.In particular,an analytical form of the differential cross section that describes a collision between an electron and the nucleus of a partially ionized atom in a plasma is proposed.The loss of energy is treated according to the continuous slowing down approximation in a plasma stopping power theory.Validation against Geant4 is presented.The code will be implemented as a module in 3D hydrodynamic codes,providing a basis for the development of robust shock ignition schemes and allowing more precise interpretations of current experiments in planar or spherical geometries.
基金This work has been carried out within the framework of the EUROfusion Enabling Research Project No.AWP17-ENR-IFECEA-01“Preparation and Realization of European Shock Ignition Experiments”and has received funding from the Euratom Research and Training Program 2014-2018 under Grant Agreement No.633053.The views and opinions expressed herein do not necessarily reflect those of the European Commission.
文摘We describe two numerical investigations performed using a 3D plasma Monte-Carlo code,developed to study hot-electron transport in the context of inertial confinement fusion.The code simulates the propagation of hot electrons in ionized targets,using appropriate scattering differential cross sections with free plasma electrons and ionized or partially ionized atoms.In this paper,we show that a target in the plasma state stops and diffuses electrons more effectively than a cold target(i.e.,a target under standard conditions in which ionization is absent).This is related to the fact that in a plasma,the nuclear potential of plasma nuclei has a greater range than in the cold case,where the screening distance is determined by the electronic structure of atoms.However,in the ablation zone created by laser interaction,electrons undergo less severe scattering,counterbalancing the enhanced diffusion that occurs in the bulk.We also show that hard collisions,i.e.,collisions with large polar scattering angle,play a primary role in electron beam diffusion and should not be neglected.An application of the plasma MonteCarlo model to typical shock ignition implosions suggests that hot electrons will not give rise to any preheating concerns if their Maxwellian temperature is lower than 25–30 keV,although the presence of populations at higher temperatures must be suppressed.This result does not depend strongly on the initial angular divergence of the electron beam set in the simulations.
