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.

As a highly automated carrying vehicle, an automated guided vehicle (AGV) has been widely applied in various industrial areas. The collision avoidance of AGV is always a problem in factories. Current solutions such as inertial and laser guiding have low flexibility and high environmental requirements. An INS (inertial navigation system)-UWB (ultra-wide band) based AGV collision avoidance system is introduced to improve the safety and flexibility of AGV in factories. An electronic map of the factory is established and the UWB anchor nodes are deployed in order to realize an accurate positioning. The extended Kalman filter (EKF) scheme that combines UWB with INS data is used to improve the localization accuracy. The current location of AGV and its motion state data are used to predict its next position, decrease the effect of control delay of AGV and avoid collisions among AGVs. Finally, experiments are given to show that the EKF scheme can get accurate position estimation and the collisions among AGVs can be detected and avoided in time.

The thin aluminum liners with an aspect ratio R/∆r 1 have been imploded on the primary test stand (PTS) facility, where R is the outer radius of the liner and ∆r is the thickness. The x-ray self-emission images present azimuthally correlated perturbations in the liner implosions. The experiments show that at −10 ns before the stagnation, the wavelengths of perturbation are about 0.93 mm and 1.67 mm for the small-radius and large-radius liners, respectively. We have utilized the resistive magnetohydrodynamic code PLUTO to study the development of magneto-Rayleigh-Taylor (MRT) instabilities under experimental conditions. The calculated perturbation amplitudes are consistent with the experimental observations very well. We have found that both mode coupling and long implosion distance are responsible for the more developed instabilities in the large-radius liner implosions.

This paper is to numerically investigate, in one dimension, the effects of precursor plasma resulted from wire-array ablation on the performance of its following implosion after the ablation. The wire-array ablation is described by an analytic model, which consists of a rocket model or Sasorov's expression of wire-array mass ablation rate, the evolution equation of magnetic field, and several roughly reasonable assumptions. The following implosion is governed by the radiation magnetohydrodynamics. The implosion processes of wire-array Z-pinch from plasma shells prefilled and un-prefilled by the low-density plasma inside them are studied, and that from the wire-array ablations, which may be changed through varying the ablation time, ablation rate, and ablation velocity V abl , are also simulated. The obtained results reveal that the prefilled low-density plasma and the precursor plasma from the wire-array ablation help to enhance the plasma shell pinch and the final implosion of the wire array, respectively, compared to the pinch of un-prefilled plasma shell. With the same plasma masses, which are distributed in the interior of the array and the shell, and modified Spitzer resistivity, the implosions that start from the wire ablation develop faster than that from the plasma shell with the prefill. If more substance ablates from the wire array before the start of its implosion, the final Z-pinch performance could be better. The Z-pinch plasma is highly magnetized with driven current more than 3 MA.

The implosion dynamics of wire-array Z-pinches are investigated numerically in 2D (r, θ) geometry by using a resistive MHD code. It is assumed that the wires have expanded to plasmas with diameter d0, which is used as the initial condition for the consequent implosion process. In fact, the explosion process of individual wires is not included. By changing d0, the effects of the wire expansion degree on the implosion dynamics are analyzed. When d0 is larger, the current density is more concentrated at the outer side of the wires and the fraction of current flow around the wire plasmas is nearly in proportion to d0. As a result, the ablation rate of wires is increased and the implosion phase starts earlier. This conclusion agrees with the simulation works of other authors [Chittenden et al., Phys. Plasmas 11(3), 1118 (2004)]. When the array radius and initial wire plasma diameter are fixed, the increase of wire number leads to the azimuthal merge of wires during implosion. When the wires number exceed a critical value, which is related to d0, wire plasmas can merge to a continuous shell with an azimuthal perturbation in density, which depends on the initial wires number.

In fast Z-pinches, rise time of drive current plays an important role in development of magneto-Rayleigh-Taylor(MRT) instabilities. It is essential for applications of Z-pinch dynamic hohlraum (ZPDH), which could be used for drivinginertial confinement fusion (ICF), to understand the scaling of rise time on MRTs. Therefore, a theoretical model for nonlinear development of MRTs is developed according to the numerical analysis. It is found from the model that the implosion distance L = r 0 – r mc determines the development of MRTs, where r 0 is the initial radius and r mc is the position of the accelerating shell. The current rise time τ would affect the MRT development because of its strong coupling with the r 0. The amplitude of MRTs would increase with the rise time linearly if an implosion velocity is specified. The effects of the rise time on MRT, in addition, are studied by numerical simulation. The results are consistent with those of the theoretical model very well. Finally, the scaling of the rise time on amplitude of MRTs is obtained for a specified implosion velocity by the theoretical model and numerical simulations.

Implosions of (quasi-)spherical loads with mass redistribution and displacement modification are investigated numerically. Both methods can theoretically counterbalance the nonuniformity of magnetic pressure along the load surface and realize quasi-spherical Z-pinch implosions. Mass redistribution is feasible for spherical loads with large radius and weight, while the displacement modification is more suitable for light loads, such as those composed of wire arrays. Simulation results suggest that, for mass redistributed spherical loads, wall instabilities induced by polar mass flows will deform the imploding shell. For prolate spherical loads, in which the wall instability cannot develop, the kinetic energy distribution is disturbed at high latitude. These passive behaviors and their possible mitigation methods, such as reshaping the electrode, are investigated numerically in this paper.

The instability evolvement induced by single mode and random density seeds have been investigated by using the Magnetics Atom Radiation Electron Dynamics ͑MARED͒ code, which is a two dimensional, three temperature, radiation magnetohydrodynamic Lagrangian code developed for the Z-pinch implosion simulation. The instability development during each stage ͑linear, weak nonlinear, and nonlinear͒ and its corresponding characteristics are studied with single-mode seeds. The evolvement of the dominant mode and its final wavelength are revealed through the development of seeds composed of modes covering the "whole" spectrum or just a "band-type" range of it. In addition, the relationship between the initial perturbation amplitude and the final x-ray output are also discussed. Through these discussions, the MARED code is found able to reproduce the primary dynamic characteristics of the Z-pinch implosions and the development of the instability qualitatively agrees with the theoretical analyses and experimental observations, which shows us a modest expectation of the broad coverage of the future application.