Numerical Investigation On Diagnosing Plasma Density Gradients By Relativistic Electron Radiography

Inertial confinement fusion seeks to release copious atomic energy by driving a pellet of cryogenic fusion with high power lasers and other sources to achieve efficient implosion and activate nuclear reactions.In the driving processes,density perturbations and steep density gradients such as ablative surfaces,shock fronts and hydrodynamic instabilities are commonly generated in targets and play profound roles in compression and even ignition.Such tiny spatial density structures indisputably require high-resolution observations.Benefited from its high-quality properties like high energy,quasi-monochromaticity,high collimation,short pulse duration and synchronization to lasers,electron bunches generated from ultra-short ultra-intense lasers interactions with matters are receiving increasingly research attentions.Compared to widely used diagnostics like X-ray radiography that relies on absorptions and proton radiography based on energy losses,motion blurring effects caused by high speed of plasma targets can largely averted when high electron probes are used because of their sources' intrinsic natures.Furthermore,investigations on electron scattering in plasmas and its characteristics can provide a new perspective for experimental data analysis and interpretations,as well as a reference for electron radiography experiment designs in diagnosing plasma steep density gradients.In the dissertation,based on relativistic electron differential cross sections on plasma ions and electrons,as well as energy loss physical models,a Monte Carlo code MCERP(Monte Carlo Electron Radiography in Plasmas)has been developed that calculates electron scattering when traversing full-ionized polystyrene plasma targets with density gradients,combined with a detector imaging system that records electron fluences.The research indicates that a typical target with a TS density profile of 1:3 density ratio(1 g/cm3 and 3 g/cm3)can reach a maximum contrast?13%on the detector.Moreover,electron source properties such as beam energy and energy spreads,target configurations including density gradient and density ratio/difference,detector positions and plasma self-generated electromagnetic fields are investigated to study the influence on electron radiography.