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The generalized computational ablation model of multi-wire Z-pinches is developed. Using derived equations, one can calculate at each moment of time both the mass ablation rate from single and nested cylindrical wire arrays as well as the matter ablation velocity. These two important variables provide the capability to numerically simulate high energy density Z-pinch experiments in a wide range of load parameters: the initial multi-wire array radius up to tens of centimeters, the inter-wire gap up to a few millimeters, the Z-pinch implosion time up to a few microseconds, and the current amplitude in a load up to tens of mega-amperes. The generalized ablation model makes it possible to reproduce the main characteristics of the Z-pinch implosion, such as the moment of starting and following movement trajectory of current-plasma sheath, timing of x-ray pulse generation, its duration, x-ray power, and total radiation energy, in radiative magneto-hydrodynamic calculations. The generalized computational ablation model of tungsten multi-wire Z-pinch was validated using results of experiments with explosive magneto-cumulative generators (Russia) and was applied further to various pulsed power generators such as Z-accelerator, PTS, MAGPIE, and Angara-5-1. [ABSTRACT FROM AUTHOR]

A dynamic Z-pinch based on a multi-wire cylindrical array having azimuthally twisted wires, called a "screw-wire array," is numerically simulated in the framework of the 3-D magneto-hydrodynamic approximation. As the current flows through the screw-wire array, an axial component of the magnetic field is generated inside, which intensifies during the radial Z-pinch implosion. The pulse parameters of the compressed magnetic field that can be recorded by a cylindrical probe arranged on the system axis are computed according to the starting twist angle of the screw-wire array. A screw-wire array is compared with a typical "flux compression" scheme in terms of their efficiencies for generating ultrahigh magnetic fields pulses. [ABSTRACT FROM AUTHOR]

Generalizations of the Dawson multibeam model are constructed, which makes it possible to analyze the stability of the system of beams with different densities in a plasma. These models can also serve as the grounds for analyzing the stability of the electron component in a plasma with a preset law of its velocity distribution. [ABSTRACT FROM AUTHOR]

Phase synchronization in a system of three virtual-cathode microwave oscillators (vircators) simulated by coupled van der Pol oscillators is studied. The phasing dynamics of the vircators is visualized with the phase portraits of the system in the triangular coordinates. Different phasing conditions are found. [ABSTRACT FROM AUTHOR]

This paper presents the results of predictive calculations of the parameters of pulses of soft X-ray radiation (SXR) on a four-module electrophysical facility GAMMA-4 (the current pulse amplitude is ~3 MA with rise time of ~60 ns) that has been constructed in Russia. Scaling numerical simulation of implosion of a cylindrical single and nested multiwire array in 0-D, 2-D, and 3-D radiation magnetohydrodynamic– approximations is performed, taking into account, the updated double-loop equivalent electrical circuit of the GAMMA-4. The main purpose of the conducted studies was the numerical optimization of the multiwire array parameters to obtain the best characteristics of the SXR pulse generated as a result of Z-pinch implosion on the axis of the system. [ABSTRACT FROM AUTHOR]

This paper demonstrates the improved simulation of a Z-pinch experiment with 2-D magnetohydrodynamic code FLUX-rz developed in RFNC-VNIIEF. A Z-pinch load was nested wire array powered by a helical magnetocumulative generator with the current pulse $I_{\max } \approx 4.2$ MA and effective rise time $\tau \approx 400$ ns. Validation of X-ray spectral measurements carried out with scintillation detector filters pointed out a necessity to take into consideration both the scintillator “dead” layer and oxide films on the aluminum filter surface. [ABSTRACT FROM AUTHOR]

This paper presents the calculation results of the initial axial magnetic field compression by the cylindrical multiwire array, powered by the pulsed power electrophysical facility Gamma. (The current pulse amplitude with 16 modules is ~11 MA, and rise time is ~60 ns.) The facility is being constructed in RFNC-VNIIEF and presently has four operating modules. [ABSTRACT FROM AUTHOR]

This paper presents the results of the experiment with an overmassed wire-array $Z$ -pinch load that is powered by a current pulse (amplitude ~4.3 MA and rise time $\sim 0.9~\mu \text{s}$) from a multidisk magnetocumulative generator. Interesting feature of the experimentally recorded soft X-ray (SXR) pulse is short (~10 ns) duration at a microsecond current rise time with total energy of several hundreds of kilojoules. Obtained results are the evidence of high-quality implosion of the current-carrying plasma. The 2-D magnetohydrodynamic code FLUX-rz was used for the numerical simulation and analysis of the obtained results. The calculations indicated that only ~30% of the initial load mass took part in the SXR generation. The main peculiarities of the overmassed $Z$ -pinch implosion are discussed in this paper. [ABSTRACT FROM AUTHOR]

Results are presented from experimental studies and numerical simulations of the effect of preliminary wire explosion on the parameters of X-ray emission generated during wire array Z-pinch implosion. The wire array implosion was driven by a current pulse with an amplitude of 0.5 MA and a rise time of 0.5 μs, while the preliminary wire explosion was produced by a current pulse with an amplitude of 0.5–1 kA per wire, a rise time of 100 ns, and a full width at half maximum of ∼200 ns. The experiments showed that the current prepulse significantly impaired the parameters of X-ray pulses. In particular, along with a decrease in the amplitude and an increase in the duration of the X-ray pulse, its spiky structure became more pronounced. The results of numerical simulations with the use of a one-dimensional radiative MHD code are in good agreement with the parameters of Z-pinch emission in experiments with and without a current prepulse. [ABSTRACT FROM AUTHOR]