关键词: 准球形电磁内爆/
Z箍缩/
动态黑腔/
薄壳模型
English Abstract
Basic dynamic and scale study of quasi-spherical Z-pinch implosion
Zhang Yang1,Sun Shun-Kai1,
Ding Ning1,
Li Zheng-Hong2,
Shu Xiao-Jian1
1.Institute of Applied Physics and Computational Mathematics, Beijing 100088, China;
2.Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900, China
Fund Project:Project supported by the National Natural Science Foundation of China (Grant Nos. 11405012, 91330107, 11275030, 11675025), the Defense Industrial Technology Development Program, China (Grant No. B1520133015), and the Foundation of President of China Academy of Engineering Physics (Grant No. 2014-1-042).Received Date:06 December 2016
Accepted Date:09 March 2017
Published Online:05 May 2017
Abstract:Unlike cylindrical Z pinch, a quasi-spherical implosion enables load plasma to implode inward spherically and concentrate its kinetic energy toward the center. This helps to improve the energy-transport efficiency and increase the shock-induced radiation intensity of the foam convertor, when the quasi-spherical implosion is used to drive a dynamic hohlraum (DH). In previous work, it has been proved that a spherical metal shell with an exact mass-distribution can implode spherically by the nonuniform magnetic field, whose magnitude increases with the load latitude, Bφ~cos-1θ. However, this ‘mass-redistribution’ method is hard to realize on the fast pulse power generator widely used in today's Z-pinch study. The rise time of the facility is only ~100 ns, and the load is wire arrays with typical weight about 1 mg/cm. We develop a method of gaining quasi-spherical implosion with wire arrays by adjusting their initial shape, and it proves feasible on the 1.5 MA Qiangguang-I facility. Recently, we try to realize the quasi-spherical dynamic hohlraum (QSDH) implosion on generator with higher current, such as the 4.5 MA Angara5-I or the 8 MA PTS facility, and to make a direct compare with its cylindrical equivalence. But first of all, a basic but relatively comprehensive study on the quasi-spherical implosion dynamics is necessary and useful for the future QSDH load design and optimization.#br#Comparing with the device for classical cylindrical Z-pinch implosions, the load and electrodes structures of quasi-spherical implosions are complex, which leads to distinct implosion dynamics and scale rules. In this paper, we develop a thin shell model for the quasi-spherical implosion, from which the movement equation, as well as the energy scale relation is derived analytically. It is found that under the same drive condition, the implosion velocity and total kinetic energy of cylindrical load are higher than those of quasi-spherical one. However, as we expected, the quasi-spherical implosion has larger kinetic energy density, which is important for the applications such as driving a dynamic holhraum. Besides the peak current, the kinetic energy of quasi-spherical implosion also depends on the initial size of the load. By increasing the initial radius and maximum latitude angle moderately, one can obtain higher kinetic energy and energy density of the implosion, which is crucial for the load design. The theoretical study is supported by simulation results. It is found that under a drive condition close to that of the ZR facility, a quasi-spherical load with an initial radius of 5 cm will reach a peak kinetic energy density of 3.2 MJ/cm, which is about 3 times those from the cylindrical ones.
Keywords: quasi-spherical implosion/
Z-pinch/
dynamic hohlraum/
thin shell model
