The Flexible Design Of The Black Cavity Configuration And The Study Of The Volume Emission Effect In The Angular Distribution Of Radiation Flow

The high-temperature and high-quality X-ray source,generated inside the hohlraum,is utilized to drive the implosion of the capsule to be centrally ignited in laser indirectly driven inertial confinement fusion(ICF),which is very meaningful to high energy density physics such as the controlled nuclear fusion.The current hohlraum configurations are required to improve the drive symmetry,coupling efficiency,and laser-plasma instabilities(LPIs).This thesis is dedicated to the hohlraum configuration design and investigations on the angular distribution of radiation flux from the hohlraum.The main research contents are as follows.1.A three dimensional view-factor code named IRAD3D is developed together to laser arrangement design and physics simulation.All the leading great laser facility models,such as the OMEGA,NIF,LMJ,and Shenguang series laser facilities,have been included in the IRAD3D.The capability of the IRAD3D is analogous to the VISRAD,such as the 3-D target model,laser arrangement design,interference check of diagnostic instruments and view field simulation,calculation of drive on the sample and radiation drive symmetry analysis,uncertainty and sensitivity analysis.This thesis is based on the IRAD3D,which has been widely used for experiment design and data analysis on Shenguang series laser facilities.2.A novel flexible hohlraum configuration design approach based on the non-uniform rational basis spline(NURBS)model is proposed to perform unified representation and optimization of current hohlraum configurations in ICF by tuning the control points and their weights,which substantially expands the design domain to enable obtaining an optimal hohlraum for any laser facility.Two new hohlraum configurations,i.e.four half-cylindrical hohlraum(FHCH)and three-axis elliptical hohlraum(TAEH),are firstly proposed to mitigate the two daunting challenges of the radiation drive asymmetry and LPIs in the conventional hohlraum configurations with two laser entrance holes(LEHs),and improve the coupling efficiency of the new configurations with much more LEHs.Single-cone laser beams are injected into the FHCH and TAEH,without cross beam energy transfer(CBET)and the attenuation of the inner-cone beams by the Au bubble.Investigations indicate that the two new hohlraum configurations have good integrated hohlraum performance,namely,excellent and robust radiation drive symmetry and acceptable plasma filling comparable to those inside the spherical hohlraum with 6LEHs(SH)and three-axis cylindrical hohlraum(TACH),in particular,much higher coupling efficiency.It is envisioned that the FHCH and TAEH should be two feasible candidates meriting investigating for indirectly driven ICF.3.A model based on the planar mesh is conducted to simulate the angular radiation flux from the LEHs,which has been validated with the calculation by VISRAD and experimental measurement on the OMEGA laser facility.The model is used to analyze the radiation flux from different detection angles on the tens of kJ laser facility in China,where the effects of the wall albedo,axis motion of laser spots,closure of the LEHs and power imbalance of the laser beams,are studied.Furthermore,the temporal evolution of the drive on the capsule and multi-angle radiation flux is also investigated.This is helpful to explore the radiation flux from a special orientation,which could be utilized to approximately characterize the balance radiation temperature within the hohlraum.However,this model will fail when the volume emission from the filling plasma could not be neglected.A modified version of the view-factor method including plasma filling is proposed.Firstly,the radial velocity of the gold bubble motion is scaled from a simple data-based model in a low gas-fill hohlraum experiment performed on the hundreds of kJ laser facility.Then an equivalent radiative volume(ERV)model is proposed to consider the contribution of the blow-off bubble in the new view-factor method embodied in IRAD3D.Then the influence of the electron density and temperature distribution,bubble velocity,and layer of bubble grid is analyzed.The simulation shows reasonable agreement with experimental data in a low-fill hohlraum without capsule.This model is helpful to perform more exact characterization of the hohlraum performance.The research of this dissertation is meaningful to design and optimize the hohlraum configuration and characterize the radiation field inside the hohlraum in laser indirectly driven inertial confinement fusion.