Study Of Electrothermal Effects On Z-pinch Magnetized Liner Inertial Fusion

Magnetized liner inertial fusion（MagLIF）represents a promising path way to con-trolled thermonuclear fusion which would provide clean,plentiful energy.The concept arise as a combination of the compression heating,characteristic of inertial confinement fusion,with the magnetic insulation and alpha heating enhancement typical of magnetic confinement fusion.MagLIF uses a cylindrical magnetized target and preheating the fuel prior to compression,and significant increment in the neutron yield when the target was magnetized has been measured,thus the advantages of fuel magnetization are demon-strated.The electrothermal effects have the potential risk to reduce the advantages of magnetization in MagLIF,which are resulted from the temperature gradient in the fuel perpendicular to the axial magnetic field,which have not aroused enough attention.Our work conducts a detailed study on this issue,and the main research contents and results are as follows:Firstly,the electrothermal effects in MagLIF are concered.The thermoelectric effect is considered in the radiation-magnetohydrodynamic model,and the axial magnetic field module including the thermoelectric effect is developed,and the MULTI-IFE code is up-graded and perfected.Considering the magnetized resistivity and electrothermal tensors in the axial magnetic field leads to frozen magnetic field,resistive magnetic diffusion,and magnetic field advection due to resistivity gradients and temperature gradients.The advection driven by the temperature gradient is electrothermal effect.Considering that the electrothermal transport in the axial magnetic field and the frictional thermal flux in the thermal conduction are coupled with each other,it is necessary to use a semi-implicit method to solve the axial magnetic field and temperature step by step,where unconditional stability is obtained without needing to solve large sparse systems of equations.Bench-mark of the energy conservation and magnetic flux conservation has been completed in the updated code,as well as the frozen-in-flow,diffusion and transport process of the axial magnetic field.Comparing this code with the classic code LASNEX,the general physical process is consistent.Therefore,the updated code is considered stable and effective.Secondly,the influence of the electrothermal effects on the magnetic field and tem-perature in the MagLIF target are researched in this thesis.The results show that the electrothermal effects aggravated theαparticles energy and thermal conduction losses,and ultimately reduced the fusion efficiency.To guarantee the driving efficiency and the stability of the liner,it is obtained that the optimal initial density range of the pure gas target is 0.003-0.0053 g·cm^-3,and the optimal inner radius of the liner is 0.27-0.36 cm.Thirdly,the Nernst thermomagnetic waves are studied in the high gain target.The steep temperature gradient in the high gain target makes the speed of the thermomagnetic waves exceed 10 km/s,the wave propagates against the temperature gradient,causing the magnetic field in the fuel decompressed.However,the high-density DT layer in the high gain target is an effective magnetic flux sink,and its magnetic field compression is significantly greater than that of a pure gas target.When considering the electrothermal effects,the fusion yield of the pure gas target MagLIF is reduced by nearly 60%,but it is only reduced by 7%in the high gain target.Fourthly,the dependence of the thermal conduction on thermal and Nernst flux lim-iter is explored,and find that in MagLIF it is not particularly sensitive to flux limiting.If the Nernst flux limiter is changed,different Nernst thermomagnetic wave speeds will be obtained as well as the fusion yield.The Nernst flux limiter between 0.1 and 0.3 prevents the thermomagnetic wave velocity from significantly reducing the pressure of the axial magnetic field and obtains a relatively high yield.Finally,a multi-shell target suitable for direct drive of low-current Z-pinch is pro-posed.The results show that under fusion conditions high radiative opacity of high-Z materials contributes to retain more energy in the fuel area.Adding a thin gold layer be-tween the gas fuel and the low-Z liner alleviates the steep temperature gradient of the fuel boundary,and helps to improve the thermal conduction and magnetic flux loss in the fuel under the influence of the electrothermal effects.Under a same driven current,the energy gain of the multi-shell target is increased by 74%.