179 / 2023-04-15 14:24:34

Experimental study of a preconditioned Z pinch with dynamic axial magnetic field generated by helical return current posts

Z pinch,critical axial magnetic field,Faraday rotation

惯性约束聚变物理学 > 其他ICF途径和脉冲功率技术-II

Z-pinch plasma is a widely recognized approach for producing plasmas with high-temperature, high-density, and high-pressure characteristics. The use of an external magnetic field for magnetic field stabilization is an effective technique to suppress the instability of plasma in Z-pinch experiments.

In this research, the impact and mechanism of dynamic axial magnetic fields on a preconditioned Z-pinch were studied. The axial magnetic field was generated by four helical return current posts, which was also the first helical post structure manufactured using 3D printing technology in Z-pinch plasma. The application of 3D printing technology can provide a way to freely change the structure of the helical posts. The load inductance, axial magnetic field, and structure strength were modeled using different helical post parameters. The influence of different return structures on each parameter was analyzed, so that the load structure could be optimized. The applied axial magnetic field distribution was obtained using a B-dot array under short-circuit loading.

Optical diagnostic methods, including shadowgraphy, interferometry, Faraday rotation, and Thomson scattering, were employed to measure the parameters of magnetized plasmas. The compression processes of azimuthal and axial magnetic fields were observed, and the suppression process of plasma instability was recorded and analyzed. The findings revealed that the dynamic axial magnetic field could be significantly compressed during the plasma implosion, with a maximum compression ratio of up to 60 times. Moreover, the external axial magnetic field could reduce the instability of plasma, but it prolonged the implosion time and weakened the radiation intensity. Furthermore, the plasma rotated during implosion and expansion with the applied axial magnetic field, and the direction of rotation was related to the direction of the radial motion of the plasma. The study provides new insights into the simultaneous investigation of mass density and magnetic field stabilization in Z-pinch plasma, and it sheds light on the mechanism and coupling process between the axial magnetic field and imploding plasma.