Effect of rear surface fields on hot, refluxing and escaping electron populations via numerical simulations  

作　　者：D.R.Rusby C.D.Armstrong G.G.Scott M.King P.McKenna D.Neely 

机构地区：[1]Central Laser Facility,STFC,Rutherford Appleton Laboratory,Chilton,Didcot 0X11 OQX,UK [2]SUPA,Department of Physics,University of Strathclyde,Glasgow G4 ONG,UK

出　　处：《High Power Laser Science and Engineering》2019年第3期76-86,共11页高功率激光科学与工程（英文版）

基　　金：funding from EPSRC Grant Nos. EP/J003832/1, EP/K022415/1, EP/R006202/1;the use of the Scarf simulation cluster

摘　　要：After a population of laser-driven hot electrons traverses a limited thickness solid target,these electrons will encounter the rear surface,creating TV/m fields that heavily influence the subsequent hot-electron propagation.Electrons that fail to overcome the electrostatic potential reflux back into the target.Those electrons that do overcome the field will escape the target.Here,using the particle-in-cell(PIC)code EPOCH and particle tracking of a large population of macro-particles,we investigate the refluxing and escaping electron populations,as well as the magnitude,spatial and temporal evolution of the rear surface electrostatic fields.The temperature of both the escaping and refluxing electrons is reduced by 30%–50%when compared to the initial hot-electron temperature as a function of intensity between 1019 and 1021 W/cm^2.Using particle tracking we conclude that the highest energy internal hot electrons are guaranteed to escape up to a threshold energy,below which only a small fraction are able to escape the target.We also examine the temporal characteristic of energy changes of the refluxing and escaping electrons and show that the majority of the energy change is as a result of the temporally evolving electric field that forms on the rear surface.After a population of laser-driven hot electrons traverses a limited thickness solid target, these electrons will encounter the rear surface, creating TV/m fields that heavily influence the subsequent hot-electron propagation. Electrons that fail to overcome the electrostatic potential reflux back into the target. Those electrons that do overcome the field will escape the target. Here, using the particle-in-cell（PIC） code EPOCH and particle tracking of a large population of macro-particles,we investigate the refluxing and escaping electron populations, as well as the magnitude, spatial and temporal evolution of the rear surface electrostatic fields. The temperature of both the escaping and refluxing electrons is reduced by 30%–50%when compared to the initial hot-electron temperature as a function of intensity between 1019 and 1021 W/cm2. Using particle tracking we conclude that the highest energy internal hot electrons are guaranteed to escape up to a threshold energy, below which only a small fraction are able to escape the target. We also examine the temporal characteristic of energy changes of the refluxing and escaping electrons and show that the majority of the energy change is as a result of the temporally evolving electric field that forms on the rear surface.

关 键 词：ELECTRON transport high power laser PARTICLE-IN-CELL simulations 

分 类 号：O57[理学—粒子物理与原子核物理]