Numerical studies of the effects of precursor plasma on the performance of wire-array Z-pinches

Ning, Cheng; Sun, Shunkai; Xiao, Di; Zhang, Yang; Ding, Ning; Huang, Jun; Xue, Cun; Shu, Xiaojian

doi:10.1063/1.3430633

Cited by 8 publications

(7 citation statements)

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“…From our simulation results, the dependence of the maximum radial velocity V a on the ratio of interwire gap/core size D g /d can be approximately expressed by the formula V a = 1.61×10 7 (1−0.8e (−Dg/3.8d) ), which is similar to that obtained from the experimental observations on MAGPIE [44]. Previous studies have shown that the existence of the precursor column resulted in higher x-ray power [45]. If the interwire separation is too small, the radial velocity of ablated plasmas would be very low and the precursor column would not be formed before the implosion phase and that might lead to decrease in x-ray power.…”

Section: Ablation and Initializationsupporting

confidence: 83%

Theoretical and numerical research of wire array Z-pinch and dynamic hohlraum at IAPCM

Ding

Zhang

Xiao

et al. 2016

Matter and Radiation at Extremes

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Dense Z-pinch plasmas are powerful and energy-efficient laboratory sources of x rays, and show the possibility to drive inertial confinement fusion (ICF). Recent advances in wire-array Z-pinch and Z-pinch dynamic hohlraum (ZPDH) researches at the Institute of Applied Physics and Computational Mathematics are presented in this paper. Models are setup to study different physical processes. A full circuit model (FCM) was used to study the coupling between Z-pinch implosion and generator discharge. A mass injection model with azimuthal modulation was setup to simulate the wire-array plasma initiation, and the two-dimensional MHD code MARED was developed to investigate the Z-pinch implosion, MRT instability, stagnation and radiation. Implosions of nested and quasispherical wire array were also investigated theoretically and numerically. Key processes of ZPDH, such as the array-foam interaction, formation of the hohlraum radiation, as well as the following capsule ablation and implosion, were analyzed with different radiation magneto-hydrodynamics (RMHD) codes. An integrated 2D RMHD simulation of dynamic hohlraum driven capsule implosion provides us the physical insights of wire-array plasma acceleration, shock generation and propagation, hohlraum formation, radiation ablation, and fuel compression.

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Section: Ablation and Initializationsupporting

confidence: 83%

Theoretical and numerical research of wire array Z-pinch and dynamic hohlraum at IAPCM

Ding

Zhang

Xiao

et al. 2016

Matter and Radiation at Extremes

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“…17 Previous studies have shown that the existence of the precursor column resulted in higher x-ray power. 27 If the interwire separation is too small, the radial velocity of ablated plasmas would be very low and the precursor column would not be formed before the implosion phase and that might lead to decrease in x-ray power. The calculational results can be used to explain the experimental observation that the x-ray power decreases once a critical wire number is exceeded.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

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

et al. 2011

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The dynamics of ablated plasmas of wire-array Z-pinches are studied numerically in (r,h) 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,h) plane. The dynamics of ablation streams determine the distribution of magnetic field and the current density J z inside the wire array. The precursor current can be approximately calculated by the integral of J z 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.

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“…In the practice of Z-pinch simulation, which is mostly based on the radiation magnetohydrodynamics equations (model), for obtaining better simulation results, which agree well with the experimental data, such as convergence ratio, and x-ray power and energy, the electrical resistivity of Zpinch plasma needs artificially modifing more or less. [12,14] The characteristic results might be obtained through this modification, but the magnetic field evolution and the pinch dynamic process might be changed unexpectedly. It is interesting and important to explore the variations of the magnetic field evolution and the dynamic process with this modification.…”

Section: Introductionmentioning

confidence: 99%

“…There are a lot of measured images from the wire-array (without preconditioning) Z-pinch experiments to demonstrate that the majority of wire-array substance has been ablated due to Joule heating and is radially swept inward towards the array axis by 𝑗 × 𝐵 force, while the wire-cores keep stationary at their original positions before its implosion begins. [7][8][9][10][11][12] So actually inside the wire-array is prefilled with ablated plasma, whose density varies with time and radius. It is possibly very low sometime and somewhere.…”

Section: Introductionmentioning

confidence: 99%

“…In most of simulations of wire-array Z-pinch, the ablation process of wire-array is ignored due to its complexity, and the wire-array is treated as a plasma shell with a precursor plasma inside, or the wires are treated as the metallic gas sources with high density and low temperature. [12,13] The metallic gas is partly ionized and expanded. The ionized gas is driven inward by Lorentz force, and a precursor plasma profile is formed.…”

Section: Introductionmentioning

confidence: 99%

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Analytical studies on the evolution processes of rarefied deuterium plasma shell Z-pinch by PIC and MHD simulations

Ning¹,

Zhang²,

Zhang³

et al. 2018

Chinese Phys. B

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In this paper, we analytically explore the magnetic field and mass density evolutions obtained in particle-in-cell (PIC) and magnetohydrodynamics (MHD) simulations of a rarefied deuterium shell Z-pinch and compare those results, and also we study the effects of artificially increased Spitzer resistivity on the magnetic field evolution and Z-pinch dynamic process in the MHD simulation. There are significant differences between the profiles of mass density in the PIC and MHD simulations before 45 ns of the Z-pinch in this study. However, after the shock formation in the PIC simulation, the mass density profile is similar to that in the MHD simulation in the case of using multiplier 2 to modify the Spitzer resistivity. Compared with the magnetic field profiles of the PIC simulation of the shell, the magnetic field diffusion has still not been sufficiently revealed in the MHD simulation even though their convergence ratios become the same by using larger multipliers in the resistivity. The MHD simulation results suggest that the magnetic field diffusion is greatly enhanced by increasing the Spitzer resistivity used, which, however, causes the implosion characteristic to change from shock compression to weak shock, even shockless evolution, and expedites the expansion of the shell. Too large a multiplier is not suggested to be used to modify the resistivity in some Z-pinch applications, such as the Z-pinch driven inertial confinement fusion (ICF) in a dynamic hohlraum. Two-fluid or Hall MHD model, even the PIC/fluid hybrid simulation would be considered as a suitable physical model when there exist the plasma regions with very low density in the simulated domain.

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Numerical studies of the effects of precursor plasma on the performance of wire-array Z-pinches

Cited by 8 publications

References 50 publications

Theoretical and numerical research of wire array Z-pinch and dynamic hohlraum at IAPCM

Theoretical and numerical research of wire array Z-pinch and dynamic hohlraum at IAPCM

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

Analytical studies on the evolution processes of rarefied deuterium plasma shell Z-pinch by PIC and MHD simulations

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