ABSTRACT Helicon wave plasma discharge (HWPD) features low operating pressure, high plasma density and superior ionization efficiency, rendering it great application potential in plasma propulsion, thin‐film deposition and fundamental plasma physics research. The High Magnetic field Helicon eXperiment (HMHX) device adopts an asymmetric Shoji antenna, yet conventional one‐dimensional (1D) and two‐dimensional (2D) numerical models fail to fully reproduce the three‐dimensional (3D) spatiotemporal evolution of plasma inside the device, and cannot accurately resolve plasma transport and energy coupling mechanisms within the diffusion‐region. In this work, a simplified 3D multi‐physics model is established to investigate the axial and radial distributions of electron density, electron temperature, plasma potential and electron‐heavy‐particle collisional power loss under the modulation of three core control parameters: radio frequency (RF) power, external magnetic field intensity and background gas pressure. The physical mechanism governing the mode transition from inductively coupled plasma (ICP) to helicon wave plasma (HWP) under parametric tuning is elaborated. Simulation results indicate that moderately elevating RF power and magnetic field strength enable efficient excitation of Helicon wave modes; nevertheless, excessive values of both parameters trigger uneven spatial plasma distribution and degraded discharge stability. Increasing background pressure suppresses ionization reactions, lowering plasma density and overall discharge performance. All three control parameters modulate radial plasma gradients, forming a characteristic “blue core” discharge structure with high central density and elevated edge electron temperature. The 3D simulation framework and parametric evolution laws proposed in this study provide solid theoretical guidance for optimizing the operating conditions of HMHX.
ABSTRACT The propagation characteristics of high‐frequency dust‐electron‐acoustic solitary waves are theoretically investigated in an unmagnetized, collisionless five‐component plasma comprising inertial cold electrons, Maxwellian‐distributed hot electrons and positrons, stationary ions, and charge‐fluctuating positively charged dust grains. Employing the standard reductive perturbation method, the Korteweg–de Vries equation is derived to describe the nonlinear evolution of dust‐electron‐acoustic waves. A key focus of this study is the dynamic charging of positively charged dust grains and their profound influence on wave propagation. Our analytical and numerical results show that, depending on the critical plasma parameters, the system supports both compressive and rarefactive solitary structures. The effect of fundamental plasma parameters and dust charge fluctuations, such as the hot electron‐to‐positron temperature ratio, the relative number densities of plasma species, and the relative dust grain potential energy, significantly modifies the phase velocity, amplitude, and width of solitary waves. These findings provide valuable insights into the nonlinear electrostatic behaviors of multicomponent plasmas in space and laboratory environments.
ABSTRACT Dusty plasmas are characterized by the formation of multiple nonlinear structures, notably including vortices. These structures, which have been observed in numerous experimental studies, are characterized by the collective motion of a large number of dust grains following a vortical trajectory around a common center located at the core of the structure. To investigate this phenomenon, several theoretical models have been developed. Recently, one such theoretical study, based on fluid equations, highlighted the role of ions in the formation of these vortex structures [Phys. Plasmas 30, 082108 (2023)]. This model is improved by incorporating two important parameters: the variation in dust grain mass resulting from the grain erosion caused by impinging plasma ions and the effect of ion–neutral collisions occurring within the plasma. The results reveal that both effects have a significant influence on the characteristics and structure of the dust vortex.
ABSTRACT We report spatial characterization of multiple wave‐coupled modes in an argon helicon plasma. Under 0.8 Pa discharge and 0.05 T axial magnetic field, increasing RF power from 800 to 2000 W produces four distinct wave modes (W1–W4) at the antenna center. Observable modes decrease axially and radially with decaying plasma density. Critical densities for mode transitions are 1.3 × 10 12 , 3.2 × 10 12 , 5.0 × 10 12 and 8.0 × 10 12 cm −3 . Low‐order W1 mode shows flat density and temperature radial profiles, while high‐order W3, W4 modes form a prominent central density peak and “blue core”. Axial wave measurements capture standing‐traveling wave patterns with phase jumps for axial wavenumber extraction. Based on helicon wave dispersion theory, we identify two transition mechanisms: axial transitions from rising axial eigenmode numbers, and radial transitions corresponding to varied radial wave structures. Multiple evidence including profile evolution and scale length variation supports our interpretation. Higher‐order mode extinction originates from insufficient local plasma density. This work builds a quantitative framework linking density thresholds to eigenmode spatial persistence to support selective mode control. Full‐vector wave field mapping is required for precise radial eigenmode verification in future studies.
ABSTRACT We study the stochastic thermodynamics for a single dust particle in a low‐temperature plasma, where it is confined by a time‐dependent parabolic trapping potential and is interacting through an ion wake potential which is generated by streaming ions. We numerically solved the overdamped Langevin dynamics through simulation to analyze the stochastic response of the dust particle to external driving for different protocol durations and strength of the ion flow. The ion wake introduces strong anisotropic forces which reshape the confinement environment, leading to complex, non‐Gaussian fluctuations. Our findings show the multi‐modal position distributions, positively skewed work statistics which satisfy the Jarzynski equality, and time‐resolved kurtosis shows the continuous deviations from Gaussianity. These findings provide a quantitative understanding of fluctuation behavior and energy dissipation in driven dusty plasma systems. We believe that this framework may serve as a basis for future investigations into transport, self‐organization, and energy conversion processes in complex plasma environments and other driven soft matter systems.
