Study On Magnetized Hohlraum

In indirect-drive Inertial Confinement Fusion(ICF),laser beams are injected into a high-Z hohlraum and are converted into quasi-symmetrical X-ray radiation field,then the radiation irradiates a low-Z capsule in the center of the hohlraum to bring the central fuel in the capsule to ignition conditions.To improve the implosion performance,the radiation field is demanding for high temperature,high symmetry,and clean radiation environment.These qualities are affected by physical processes in the hohlraum,including hot electrons emission due to the interaction between laser and plasma,pre-heating of the capsule by M-band radiation emitted from corona plasma,plasma filling in the hohlraum caused by corona plasma motion which affects the propagation of the laser,laser spots movement on the hohlraum wall which affects the time-varied asymmetry of the radiation field,etc.To mitigate these problems,magnetic field was introduced to the conventional hohlraum.The interaction between laser and magnetized hohlraum was studied,including the following three aspects:1.Development of simulation codes for radiation magnetohydrodynamics(RMHD):Magnetic field module was added to Multi-ID(an open source code of radiation hydrodynamics),which made a 1D code of RMHD named Multi-1D-M.One this basis,a new 1D code of RMHD named Icefire-1D was developed.Icefire-1D and Multi-1D-M form the 1D simulation platform for RMHD.Furthermore,the corresponding 2D code named Icefire-2D was developed as well after several years efforts.Icefire-2D uses cylindrical coordinate,and it takes most of the physical issues into consideration,including 3D laser tracing,RMHD revolution,electron heat conduction,electron-ion energy transfer,etc.It provides a important 2D simulation platform for research of RMHD in ICF.2.Numerical simulation of magnetized hohlraum:numerical simulations were carried out on magnetized hohlraum based on the developed 1D and 2D codes.The magnetic field varies from about 10T to 1000T.For magnetic field of 10T order,the research focused on the flux limiting effect of magnetic field on electron heat conduction.For magnetic field of 100T order,the research focused on the dynamic effects of magnetic field,the influence of Lorenz force on the spatial distributions of plasma temperature and density was studied.For magnetic field of 1000T order,exploration was made to generate ultra-high temperature radiation source by laser irradiated small-size magnetized hohlraum.Through the study of a series of numerical cases,the influence of different magnetic field intensity on the performance of the hohlraum was obtained.3.Experimental demonstration of magnetized hohlraum:the experiment of laser irradiated magnetized hohlraum was conducted on the SGII laser facility.The mega Gauss magnetic field pulse was generated by the interaction between the ninth laser beam and the capacitor-coil target.The strong magnetic field was coupled into the hohlraum,which made a magnetized hohlraum,and afterwards 8 laser beams were injected into the hohlraum,to study the interaction of laser and magnetized hohlraum.The effect was observed that radial motion of wall plasma was suppressed by magnetic field.The research of this thesis established numerical simulation platform for RMHD in ICF,and both numerical simulation and experimental research were conducted on the magnetized hohlraum,providing important reference for strong magnetic field application to conventional hohlraum physics in ICF.