Axial Symmetric3D Reconstruction Method Of Plasma In Laser Fusion Experiments

With the further research of ICF, there is an urgent need to develop the morecomprehensive, accurate plasma diagnostic technique. In laser fusion experiments, thecompression symmetry and uniformity of core is one of the key factors to realize targethigh temperature and high density.Plasma3D reconstruction is the technique of using X-ray detection images to threedimensional reconstruction, in order to obtain the three dimensional distribution ofplasma parameters. With the X-ray detection images reconstruct the spatial distributionof laser plasma emission coefficient and absorption coefficient, obtain about thecompression symmetry, electronic temperature, electronic density and other importantphysical information, is an important means of laser plasma diagnostic.The main work of this thesis is to establish an X-ray forward transmission modeland imaging model in laser plasma, research and development of laser plasma3Dreconstruction technique, thereby reconstructing the emission coefficient and absorptioncoefficient. The thesis is composed of three parts:Firstly, study the traditional image based3D reconstruction techniques, includinganalytical method, the algebraic reconstruction technique and statistical iterative method,and Abel transformation theory. Due to Abel inverse transformation reconstructionmethod ignore the absorption effect, reconstruction error is larger, and can onlyreconstruct the emission coefficient.Secondly, in the simplified case, established the X-ray forward transmission modelin laser plasma, Monte Carlo and numerical integration method respectively are used toget the detection images. The results are briefly discussed: although plasma absorptioncoefficient is very small, has a great influence on the detected images.Thirdly, introduced optical computed tomography technology (OCT) and emissionspectral tomography technology (EST). According to the laser plasma X-ray imagingcharacteristics, build a layered structure imaging model, using LM (Levenberg-Marquardt) nonlinear least squares algorithm, a novel reconstruction algorithm isproposed, and the numerical simulation is done. The results show that: this algorithmcould successfully reconstruct the emission coefficient and absorption coefficient. Inlitter noise cases, can be almost exact reconstruction, significantly better than thereconstruction results of Abel inverse transformation.