Contributions to Plasma Physics最新文献

Fast and reliable plasma chemistry plays a crucial role in the fabrication of micro- and nanoscale structures in numerous applications. In this work, we demonstrated that fast and optimal etch chemistry using an inductively coupled plasma (ICP) system in combination with a simple and cost-effective dry film photoresist (DFR) as a mask transfer. The results show that the proposed DFR, which simultaneously removes the edge bead and air bubbles, can be successfully used in chlorinated and fluorinated chemistries, resulting in fast etching rates and good selectivity from 5:1 to 16:1 for GaAs and from 30:1 to 150:1 for silicon substrates. This solution offers the promise of drastically cutting down microfabrication time and minimizing contamination. It could pave the way for a novel, rapid manufacturing process that is applicable in various fields, regardless of the size or shape of the substrate.

Irradiation effect on the different plasma modes in various dusty plasma conditions was studied theoretically. We revisit our investigation on the instability of the electrostatic dust acoustic (DA) mode elaborately in the case of ionospheric dusty plasmas. In this investigation, it is found that the growth rate of DA mode increases two orders more due to the photoelectric effect than that of the streaming effect. A detailed description of the dust charge fluctuation model in the irradiated dusty plasmas, the derivation of the DA mode, and discussions on the numerical analysis of the obtained results make the paper easy to understand. The present theory should be applied specially in understanding the formation of radar echoes in the presence of solar radiation.

We have studied the circular polarised Terahertz (THz) wave emission by mixing of two lasers in plasma when an externally applied helical structured electric field is present. A nonlinear transverse current density at difference frequency emerges on the accounts of ponderomotive nonlinearity. This occurs when the electrons moving under the influence of externally applied helical electric field, couples with the nonlinear plasma density at difference frequency. This transverse current density can be decomposed of two mutually perpendicular vector having equal amplitude and $��\pi �/�2�$ phase shift, which drives a circular polarised coherent THz radiation. It turns out that conversion efficiency of THz radiation substantially depends on electron plasma frequency, mismatch phase, polarisation angle between laser beams and externally applied helical electric filed. Numerical simulations show that the conversion efficiency increases as THz frequency approach to plasma frequency.

This paper presents the multi-species global impurity transport capability developed in a GPU-accelerated fully 3D unstructured mesh-based code, GITRm, to simultaneously track multiple impurity species and handle interactions of these impurities with mixed-material surfaces. Different computational approaches to model particle-surface interaction or surface response have been developed and compared. Sheath electric field is taken into account by employing a fast distance-to-boundary calculation, which is carried out in parallel on distributed or partitioned meshes on multiple GPUs without the need for any inter-process communication during the simulation. Several example cases, including two for the DIII-D tokamak, that is, one with the SAS-V divertor and the other with the collector probes, are used to demonstrate the utility of the current multi-species capability. For the DIII-D probe case, the capability of GITRm to resolve the spatial distribution of particles in localized regions, such as diagnostic probes, within non-axisymmetric tokamak geometries is demonstrated. These simulations involve up to 320 million particles and utilize up to 48 GPUs.

In this study, we developed a model to explore the characteristics of a magnetized plasma sheath, containing positive ions, electrons, and neutral particles. The ions are described using a fluid model based on the continuity and momentum equations, while the electron distribution is analyzed using three cases: the Maxwell–Boltzmann distribution and the Tsallis distribution in both 1-D and 3-D velocity spaces. Applying the Sagdeev method, we established the modified Bohm sheath criterion to obtain the required ion velocity at the sheath entrance for all three cases. The lower Mach number limit for Bohm velocity modification depends on factors such as ion temperature, ionization frequency, collision frequency, magnetic field angle, nonextensive parameter $��q�$, and the velocity space governing the density of nonextensive electrons, independent of magnetic field magnitude. Additionally, the electron velocity distribution was analyzed for various q-values, revealing that in 3-D velocity space, the energy range is broad and extensive, while in 1-D velocity spaces, it is narrower and confined within the broader 3-D interval. We examined the influence of key parameters on sheath characteristics under the Maxwellian distribution, as well as in 1-D and 3-D velocity spaces for the Tsallis distribution. The results demonstrated significant differences between the three cases, showing that in the 3-D case, the sheath thickness expands more compared to the 1-D and the Maxwell–Boltzmann distribution. This underscores the significance of accounting for the dimensionality of velocity space when investigating plasma sheath phenomena. Such understanding is crucial for optimizing plasma-surface interactions in various applications.