Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-...Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray radiography.By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and contrast.Using constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil targets.Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays.展开更多
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 propa...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.展开更多
基金supported by EPSRC grants EP/K022415/1and EP/R006202/1the STFC IPS grant ST/P000177/1
文摘Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray radiography.By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and contrast.Using constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil targets.Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays.
基金funding from EPSRC Grant Nos. EP/J003832/1, EP/K022415/1, EP/R006202/1the use of the Scarf simulation cluster
文摘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.
