Regular Article

Geometrical optimization of quasi-spherical wire-array implosion

Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, P.R. China

^a e-mail: chuyanyun@caep.cn

Received: 18 April 2017
Received in final form: 4 June 2017
Published online: 2 November 2017

Abstract

A geometrical optimization method based on the multi-element model is developed for electromagnetic implosion of quasi-spherical wire-array loads. The shapes of the initial quasi-spherical wire arrays are described with the parabolic formation, and the shapes of the final plasma shells are estimated with the multipole expansion method. By scanning the aspect ratios of the initial loads, we can obtain the most nearly-spherical final plasma shell with certain mean radius, i.e. the shell has the smallest quadrupole and hexadecapole deformation. As a typical case, starting with the preshaped cylindrical load (with height of 15.4 mm and with diameter of 8 mm), the imploding plasma shell with mean radius of 1.5 mm is almost spherical when the initial aspect ratio takes the value of 1.089, and the results is consistent with the synchronization analysis. The optimization calculations for different current waveforms and different initial load masses indicate that the shape of the optimized plasma shell is not sensitive to the drive current and load mass. The geometrical optimization method here can be served as a primary designing tool for the quasi-spherical wire-array load.