Development And Application Of Optical Collective Thomson Scattering Diagnostics

In the research of inertial confinement fusion,the neutron yield predicted with radiation hydrodynamic simulation systematically deviates from the experimental observations.It suggests that there are still important physical processes that are not included in the existing radiation hydrodynamic models,resulting in the failure to achieve fusion ignition as expected.The high accuracy of physical modeling requests a higher requirement on the diagnostic accuracy of plasma parameters.In this thesis,a new method to optimize the diagnostic accuracy of optical Thomson scattering is proposed,and validation experiments are carried out to address the research needs of laser-plasma physics in the corona region.The transport processes in non-uniform plasma are experimentally investigated with the new Thomson scattering diagnostic method.The results of the Thomson scattering diagnostic method and theory in this thesis are as follows:1)A multi-angle Thomson scattering diagnosis method is proposed.The Monte-Carlo simulation analysis shows that this method can significantly improve the precision and accuracy of plasma parameters.2)In terms of data processing methods,the least-square fitting and uncertainty analysis are introduced to systematically analyze the diagnostic method’s characteristics,thereby optimizing the experimental design.3)It is clarified theoretically that the thermal force coefficient is related to generalized electron-ion drift velocity.It is proposed for the first time to use the asymmetry of the Thomson scattering ion-acoustic resonance peak to diagnose the thermal coefficient.In order to verify the multi-angle Thomson scattering diagnostic method,we conducted experiments on the Joule-level laser device.In addition to diagnosing two-angle time-evolving ion-acoustic-wave features of the spectra simultaneously,holographic interference diagnosis and single-angle electron-plasma-wave feature of the spectra were also arranged for electron density diagnosis.It is confirmed that this method can diagnose electron density,compared with the single-angle ion-acoustic-wave feature diagnosis.The precision of electron density is improved from the original over 100%to～30%.We also carried out a three-branch Thomson diagnosis on the Shenguang-180 kJ facility.Although the dual-angle Thomson scattering diagnosis failed to give a valid electron density due to the insensitivity in such conditions,the precision of electron temperature increased to～10%.In addition,experimental studies have shown that the dual-angle Thomson scattering diagnosis is suitable for the scattering parameters a in the range from 1 to 2.We find that the asymmetry of the ion-acoustic-wave feature of Thomson scattering spectrum is closely related to the thermal force coefficient of electrons,which provides a new idea for studying electron transport driven by temperature gradients via Thomson scattering.We combined the radiation hydrodynamic fluid simulations and Fokker-Planck simulations to give the evolution of the thermal force coefficient at different spatial positions.When there are non-local effects,the thermal force coefficient deviates significantly from the local theory.By analyzing the results of Joule-level experiments,we give the experimental evolution of the thermal coefficient for the first time,which is close to the simulation results’ trend,although the details differ from the simulated results.