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Dense plasma focus (DPF) is a pulsed high current discharge device, which is widely used in particle accelerator, controlled nuclear fusion, space propulsion and pulsed neutron source. However, existing models for DPF dynamics, including semi-empirical snowplow approximations and particle-in-cell (PIC) methods, face limitations in balancing computational efficiency with comprehensive physical descriptions. In contrast, magnetohydrodynamic (MHD) models enable comprehensive analysis of macroscopic phenomena (e.g., sheath motion, current distribution, fluid instabilities) and parametric impacts (e.g., electrode geometry, gas pressure, driving current waveforms) on DPF performance. Although MHD cannot self-consistently resolve kinetic behaviors like high-energy particle beams or neutron production during pinch phases, it remains highly valuable for investigating macroscopic DPF physics when quantitative neutron yield analysis is unnecessary. Therefore, a two-temperature MHD model coupled with an external RLC circuit is developed in this paper, incorporating electron-ion thermal nonequilibrium, resistive effects, and plasma transport coefficients derived from Braginskii formulations. The model is rigorously validated against experimental data from two benchmark DPF devices (UNU and UDMPF1), demonstrating excellent agreement in current waveform, voltage profile, and radial implosion trajectory. The research shows that the DPF plasma sheath is continuously accelerated along the axial direction under the action of the Lorentz force. When it moves to the end of the inner electrode, the plasma sheath bends radially inward and is eventually compressed on the symmetry axis to form high-temperature and high-density plasma. For the UNU device, simulations reveal distinct plasma evolution phases: (1) Axial acceleration (0–2.5 μs), where the current sheath attains velocities up to 90 km/s under Lorentz force dominance, with ion temperatures rising from 1 eV to 100 eV. (2) Radial implosion (2.78–2.90 μs), during which plasma density increases by an order of magnitude (to ~10²⁴ m⁻³) and ion temperatures surge to ~1 keV through magnetically driven compression. Further studies also find that for large DPF devices, reducing the inductance and increasing the capacitance, the circuit current is prone to saturation; while increasing the circuit voltage has a more significant effect on the current increase. This paper shows that for large DPF devices, the ratio of the anode radius to cathode radius needs to be as small as possible, which can increase the peak current and pinch current of DPF as much as possible under the condition that other parameters remain unchanged.
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Keywords:
- Dense plasma focus /
- magnetohydrodynamic simulation /
- plasma acceleration /
- pinch
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