Contributions to Plasma Physics最新文献

Considerable interest has emerged in atmospheric pressure discharges within the microwave frequency range over the past decade, driven by the growing potential applications such as material processing, CO₂ dissociation, waste treatment, hydrogen production, water treatment, and so forth. This review delves into the diverse types of atmospheric pressure plasma jets (APPJs) operated at microwave frequencies. The analysis integrates insights from an overall review that encapsulates the different types of geometry, characterizations, modeling, and various applications of microwave atmospheric plasma jets (MW-APPJs). This paper will contribute to a comprehensive understanding of microwave plasma generated in the ambient atmosphere. The fundamental insights into these discharges are emerging, but there are still numerous unexplained phenomena in these inherently complex plasmas that need to be studied. The properties of these MW-APPJs encompass a higher range of electron densities (n_e), gas temperatures (T_g), electron temperatures (T_e), and reactive oxygen and nitrogen species (RONS). This review provides an overview of the key underlying processes crucial for generating and stabilizing MW-APPJs. Additionally, the unique physical and chemical properties of these discharges are summarized. In the initial section, we aim to introduce the primary scientific characterizations of different types of waveguide-based and non-waveguide-based MW-APPJs. The subsequent part focuses on the diverse modeling approaches for different MW-APPJs and the outcomes derived from these models. The final section describes the potential applications of MW-APPJs in various domains.

The structure and phase transition of a two-dimensional $���\left(��2�D��\right)��$ dusty plasma, confined by an anisotropic power-law potential and interacting via a screened Coulomb potential, were investigated using Monte Carlo simulations. The study varied the number of particles ($��N�$), screening strength ($��k�$), eccentricity parameter ($��\alpha �$), and confinement power parameter ($��n�$) to characterize the system's structural properties. According to the simulation results, the melting temperature is influenced by the eccentricity parameter. Reducing the eccentricity results in a corresponding decrease in the melting temperature. However, the confinement power parameter does not appear to have any impact on the melting temperature.

A new integrating model has been developed to couple tokamak edge multiscale magnetohydrodynamic (MHD) events and transport simulations, such as edge-localized mode (ELM) cycles. As a proof of principle, we first start from a set of three-field two-fluid model equations, which includes the pressure, current, and vorticity. The equations are separated into the slowly evolving part of the axisymmetric component by taking a time average of the axisymmetric component. The time-averaged fluxes, which are quadratic in fluctuating quantities, act as driven terms for the time-averaged axisymmetric quantities that determine the plasma transport, and therefore the large-scale evolution of the plasma profiles. Then the HL-2A's ELM cycles are simulated using the model. Good agreements of ELM size and pedestal recovery time have been achieved for the solutions obtained from the coupled simulation compared with experiment. For one ELM cycle simulation, the coupled code can achieve a speedup of a factor of up to 30 over standalone code.

The wave-breaking amplitude of a strong nonlinear plasma wave has been determined in a warm plasma. Pseudopotential technique has been adopted to describe the wave-breaking phenomena in such plasma. The solution is obtained with the consideration that the phase velocity of the plasma wave is equal to the velocity of light in vacuum. This assumption is justified since the wave which is excited usually by the relativistic charged particle bunches or laser pulses has phase speed very close to the speed of light in vacuum. The investigation shows that the breaking amplitude decreases with the increase of the electron temperature. Furthermore, the wavelength of the plasma wave is seen to decrease as we increase the electron temperature. The obtained results have relevance in the astrophysical situation as well as in the field of plasma based charged particle acceleration process.

Ken Golden (top photo) and Gabor Kalman (bottom photo). Photos by P. Hartmann.

This manuscript examines the non-linear interaction between the negative energy beam cyclotron mode and the high-frequency whistler waves. The negative energy beam mode is supported in the vicinity of the beam gyro-frequency harmonics by a gyrating ion beam with $��a�$ ring-shaped velocity distribution. Using a gyrating ion beam, we have examined how dust charge variations affect the parametric up-conversion of high-frequency whistler waves (WWs) into a side band wave and a low-frequency mode. For the linked modes, a non-linear dispersion relation is obtained. It is demonstrated that the WWs divided by beam gyro-frequency harmonics are up-converted by a gyrating ion-beam frequency. An expression for the ion cyclotron mode wave growth rate has been obtained. The estimation of the turbulence growth rate takes into account for the typical parameters of existing dusty plasma. It has been observed that an increased growth rate is reported with a rise in the pump wave amplitude, beam gyro-frequency, number density of dust grains, and the relative density of dust grains. However, a decline in the growth rate has been observed with increasing gyrating ion beam density and dust grain's size.

A study of multi-ion species plasmas in divertor region through kinetic simulation helps us understand particle transports and wall interactions. We analyzed plasma sheath behavior without collisions involving electrons, hydrogen isotopes, and helium ions using a one-dimensional spatial space and three-dimensional velocity space (1D3V) Particle-In-Cell (PIC) simulation. The PIC simulation model follows Maxwellian velocity distributions with the pre-sheath acceleration for each particle species in the plasma source, and the plasmas move to the absorption wall with equal and constant flux. This revealed spatial potential variations due to differences in masses and charges of multi-ion species plasmas, including independent sound velocities of each ion species. Increasing ion masses result in a more negative wall potential. The electrostatic force repels electrons and accelerates multi-ions to reach the absorption wall. This information is found in the phase spaces of velocity in the sheath.