Effects of secondary electron emission on plasma characteristics in dual-frequency atmospheric pressure helium discharge by fluid modeling

Based on the rough surface topography with fractal parameters and the Monte–Carlo simulation method for secondary electron emission properties, we analyze the secondary electron yield (SEY) of a metal with rough surface topography. The results show that when the characteristic length scale of the surface, G, is larger than 1 × 10−7, the surface roughness increases with the increasing fractal dimension D. When the surface roughness becomes larger, it is difficult for entered electrons to escape surface. As a result, more electrons are collected and then SEY decreases. When G is less than 1 × 10−7, the effect of the surface topography can be ignored, and the SEY almost has no change as the dimension D increases. Then, the multipactor thresholds of a C-band rectangular impedance transfer and an ultrahigh-frequency-band coaxial impedance transfer are predicted by the relationship between the SEY and the fractal parameters. It is verified that for practical microwave devices, the larger the parameter G is, the higher the multipactor threshold is. Also, the larger the value of D, the higher the multipactor threshold.

Section: Introductionmentioning

confidence: 99%

Analysis of secondary electron emission using the fractal method*

Bai

et al. 2021

“…Since the electron mean free path is much smaller than the electrode gap, the arc and near-cathode sheath formation process can be described by a fluid method. [54]…”

Section: Geometric Model and Basic Assumptionsmentioning

confidence: 99%

“…The electron number density conservation equation, electron energy density conservation equation, and electron momentum conservation equation are obtained by solving the electron continuity equations [38,[54][55][56][57] ∂ n e ∂t…”

Section: Electron Transport Equationsmentioning

confidence: 99%

Fluid-chemical modeling of the near-cathode sheath formation process in a high current broken in DC air circuit breaker

Peng

Duan

et al. 2023

When the contacts of medium-voltage DC air circuit breaker (DCCB) are separated, the energy distribution of arc is determined by the formation process of near electrode sheath. So, the voltage drop through the near electrode sheath is an important means to build-up the arc voltage, which determines the current-limiting performance of the DCCB directly. A numerical model describing the near electrode sheath formation process can provide insight into the physical mechanism of the arc formation and thus provide a method for arc energy regulation. In this work, a two-dimensional axisymmetric time-varying model of a medium-voltage DCCB arc when high-current interrupted was established based on a fluidchemical model involving 16 kinds of species and 47 collision reactions. The transient distributions of electron number density, positive and negative ion number density, net space charge density, axial electric field, axial potential between electrodes and near cathode sheath were obtained from the numerical model. The computational results show that the electron density in the arc column increases, then decreases, and then stabilizes during the near cathode sheath formation process, and the arc column diameter gradually becomes wider. The 11.14–12.33 V drops along the 17 µm space charge layer away from the cathode (65.5–72.5 kV/m) when the current is verying from 20–80 kA. The homogeneous external magnetic field has little effect on the distribution of particles in the near cathode sheath core, but the electron number density at the near cathode sheath periphery can increase with the magnetic field increasing and the homogeneous external magnetic field will lead to arc diffusion. The validity of the numerical model can be proved by comparison with the experiment.

“…The SEE is an important process in surface physics with applications in numerous fields, such as microchannel tube, [3] plasma display screen, [4] photomultiplier tube, [5] scanning electron microscope, [6] etc. The SEE can also adversely affect the applications and performance of devices, such as particle accelerator, [7] spacecraft surface, [8,9] fusion plasma, [10] RF/DC bias plasma process discharge, [11,12] Hall and spiral wave plasma thrusters, [13,14] etc. In plasma, strong SEE can significantly increase the electron heat flux from the plasma to the wall, resulting in (i) wall heating and wall evaporation, and (ii) plasma cooling and even extinction.…”

Section: Introductionmentioning

confidence: 99%

Secondary electron emission yield from vertical graphene nanosheets by helicon plasma deposition

Jin¹,

Ji²,

Zhuge³

et al. 2022

The secondary electron emission yields of materials depend on the geometries of their surface structures. In this paper, a method of depositing vertical graphene nanosheet (VGN) on the surface of the material is proposed, and the secondary electron emission (SEE) characteristics for the VGN structure are studied. The COMSOL simulation and the scanning electron microscope (SEM) image analysis are carried out to study the secondary electron yield (SEY). The effect of aspect ratio and packing density of VGN on SEY under normal incident condition are studied. The results show that the VGN structure has a good effect on suppressing SEE.