Plasma-Surface Interactions Within Helicon Plasma Sources

Valle, Juan I. Del; Díaz, Franklin R. Chang; Granados, Victor H.

doi:10.3389/fphy.2022.856221

Cited by 6 publications

(7 citation statements)

References 81 publications

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“…Figure 1A) presents an idealized diagram of a helicon plasma source (HPS), showing its main components in a typical cylindrical configuration, as well as the coordinate system defining the simulation domain. Figure 1B), reproduced from [2], describes the two main modes of erosion phenomena within the plasma-facing components of HPSs, as described in the literature.…”

Section: Mathematical Modelsmentioning

confidence: 84%

“…In a previous paper [2], we have contributed a review of this topic and the different phenomena involved in its analysis, and described past published work addressing erosion phenomena within HPS. Among those, Berisford et al [3] conducted experimental measurements of the etching phenomena on the inside of a quartz tube used as dielectric boundary in a helicon source.…”

Section: Open Access Edited Bymentioning

confidence: 99%

“…Sputtering depends on several parameters, including the properties of the impinging particles, the composition of the target material surface and the geometry of the impact. A simplified model for the geometry of the sputtering process [2] describes the incoming ion being accelerated by the potential drop on the sheath to an energy E 0 until it impacts the surface with an angle θ with respect to the surface normal. If the energy surpasses a threshold level for the occurrence of sputtering, E 0 > E thr , a cascade of collisions within the target material will be able to provide sufficient momentum to one or several particles in the top layer of the target material, and allow them to overcome the surface binding energy E sb and leave the surface.…”

Section: Sputtering Phenomenamentioning

confidence: 99%

“…This DC sheath is present along all plasma-facing boundary surfaces. Region (2) in the diagram describes the interaction Experimental data obtained from the typical operation configuration of the VX-CR helicon plasma source, adapted from [22]. (A) shows the measurements of the peak voltage V p in the VX-CR helicon antenna, measured at the external RF feed line, as a function of the measured RF forward power coupled into the system.…”

Section: Practical Estimation Of Erosion Within Hpssmentioning

confidence: 99%

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Estimation of erosion phenomena within helicon plasma sources through a steady-state explicit analytical model

Valle

Granados

Díaz³

2022

Front. Phys.

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Helicon plasma sources produce high-density discharges without the need of electrodes in direct contact with the plasma, which is thought to provide them with long operational lifetimes. An explicit steady-state analytical model is described with the capability of depicting the 2D plasma density distribution, the sheath potentials and the estimated sputtering and etch rates along the plasma-facing components of the source. The individual constituting submodels are fitted against available experimental data, and the model is used to predict erosion rates within the VX-CR research helicon plasma source. Erosion within these components is dependent on the value of plasma density along the boundaries, the electron temperature and the particular ion-target material combination. The highest erosion rates are found along the upstream system boundary, followed by the regions near the helicon antenna straps where a capacitive RF sheath is formed. The assumptions and limitations of the model are discussed, and future improvements are proposed.

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Section: Mathematical Modelsmentioning

confidence: 84%

Section: Open Access Edited Bymentioning

confidence: 99%

Section: Sputtering Phenomenamentioning

confidence: 99%

Section: Practical Estimation Of Erosion Within Hpssmentioning

confidence: 99%

See 2 more Smart Citations

Estimation of erosion phenomena within helicon plasma sources through a steady-state explicit analytical model

Valle

Granados

Díaz³

2022

Front. Phys.

Self Cite

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“…A sheath becomes emissive due to surface emission processes, including secondary electron emission (SEE), backscattering, field emission, thermionic emission, photoemission, etc. Emissive sheath widely appears in confined laboratory plasmas and plays a vital role in numerous industrial plasma applications such as plasma processing, electric proportion, plasma diagnostics, plasma source and many others (1)(2)(3)(4). The present research focuses on the algorithms to implement the interactions between plasma and dielectric surface in the kinetic simulation and the underlying sheath physics.…”

Section: Introductionmentioning

confidence: 99%

Vlasov simulation of the emissive plasma sheath with energy-dependent secondary emission coefficient and improved modeling for dielectric charging effects

et al. 2022

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A one-dimensional Vlasov–Poisson simulation code is employed to investigate the plasma sheath considering electron-induced secondary electron emission (SEE) and backscattering. The SEE coefficient is commonly treated as constant in a range of plasma simulations; here, an improved SEE model of a charged dielectric wall is constructed, which includes the wall charging effect on the SEE coefficient and the energy dependency of the SEE coefficient. Pertinent algorithms to implement the previously mentioned SEE model in plasma simulation are studied in detail. It is found that the SEE coefficient increases with the amount of negative wall charges, which in turn reduces the emissive sheath potential. With an energy-dependent SEE coefficient, the sheath potential is a nonlinear function of the plasma electron temperature, as opposed to the linear relation predicted by the classic emissive sheath theory. Simulation combining both wall-charging effect and SEE coefficient’ energy dependency suggests that the space-charged limited sheath is formed at high plasma electron temperature levels, where both sheath potential and surface charging saturate. Additionally, different algorithms to implement the backscattering in the kinetic simulation are tested and compared. Converting backscattered electrons to secondary electrons via an effective SEE coefficient barely affects the sheath properties. The simulation results are shown to be commensurate with the upgraded sheath theory predictions.

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Uncover Chemical Processes for Silica Surfaces Exposed to Atomic Oxygen Using ReaxFF Reactive Molecular Dynamics

Ye,

Hu,

Zhang

et al. 2024

J. Phys. Chem. C

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The considerable level of uncertainty in the measured and calculated catalytic recombination coefficients of atomic oxygen (O) on silica (SiO 2 ) surfaces has posed a great challenge to the accurate prediction of heating load and thereby the weight-effective design for atmospheric hypersonic vehicles. This work conducts large-scale (in terms of reaction trajectories) reactive molecular dynamics simulations based on ReaxFF SiO GSI , a ReaxFF potential function tailored for O(gas)-SiO 2 (surface) interactions to understand the chemical processes for the recombination of O for different SiO 2 surface structures. The applicability of the present ReaxFF-based molecular dynamics is validated by the density-functional-theory calculation through O adsorption on the same SiO 2 surface structures under investigation.An automatic data analyzer is developed to capture the reaction pathways and mechanisms from the vast amount of trajectories. It is found that the pathways of adsorption, active site formation, and recombination are sensitive to the surface structures. The overall recombination coefficient and its compositions from different reaction pathways vary considerably for different surface structures. We identify for the first time a reaction mechanism involving multiple active sites, which is more likely to occur than the single-site reactions and thus can potentially increase the recombination probability. These findings highlight the important role of surface structure in catalytic recombination reactions and provide a possible explanation for the huge discrepancy in the recombination coefficients from previous studies.

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Plasma-Surface Interactions Within Helicon Plasma Sources

Cited by 6 publications

References 81 publications

Estimation of erosion phenomena within helicon plasma sources through a steady-state explicit analytical model

Estimation of erosion phenomena within helicon plasma sources through a steady-state explicit analytical model

Vlasov simulation of the emissive plasma sheath with energy-dependent secondary emission coefficient and improved modeling for dielectric charging effects

Uncover Chemical Processes for Silica Surfaces Exposed to Atomic Oxygen Using ReaxFF Reactive Molecular Dynamics

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