TITLE

Numerical studies of ablated-plasma dynamics and precursor current of wire-array Z-pinches

AUTHOR(S)
Huang, Jun; Sun, Shun-Kai; Ding, Ning; Ning, Cheng; Xiao, De-Long; Zhang, Yang; Xue, Chuang
PUB. DATE
April 2011
SOURCE
Physics of Plasmas;Apr2011, Vol. 18 Issue 4, p042704
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
The dynamics of ablated plasmas of wire-array Z-pinches are studied numerically in (r,θ) geometry by using the magnetohydrodynamic (MHD) simulation model in which the mass injection boundary conditions are presented, and two-dimensional spatio-temporal distributions of magnetic field and precursor current during the ablation phase are obtained. The ablated-plasma dynamics contains four processes: drifting toward the axis, arriving at the axis and forming the precursor column, and contraction and expansion of the precursor column. The relationship among the maximum inward velocity of ablated plasma streams and the initial wire array parameters is analyzed and it is found that this velocity is relatively sensitive to the change of inter-wire separation but weakly depends on the original array radius. The results are in reasonable agreement with the experiments on MAGPIE facility. The origin of the current flow in the precursor plasmas is analyzed from the point of view of the B-field convection in (r,θ) plane. The dynamics of ablation streams determine the distribution of magnetic field and the current density Jz inside the wire array. The precursor current can be approximately calculated by the integral of Jz inside the region of a radius near to the column. In this model, the fraction of precursor current is less than 10% of the total current, which is close to the experimental results. When the current waveform is fixed, the increase of the inter-wire gap or decrease of the initial radius will lead to the increase of the precursor current.
ACCESSION #
60313466

 

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