Plasma assisted combustion: Dynamics and chemistry

Journal of Physics D: Applied Physics published the first Plasma Roadmap in 2012 consisting of the individual perspectives of 16 leading experts in the various sub-fields of low temperature plasma science and technology. The 2017 Plasma Roadmap is the first update of a planned series of periodic updates of the Plasma Roadmap. The continuously growing interdisciplinary nature of the low temperature plasma field and its equally broad range of applications are making it increasingly difficult to identify major challenges that encompass all of the many sub-fields and applications. This intellectual diversity is ultimately a strength of the field. The current state of the art for the 19 sub-fields addressed in this roadmap demonstrates the enviable track record of the low temperature plasma field in the development of plasmas as an enabling technology for a vast range of technologies that underpin our modern society. At the same time, the many important scientific and technological challenges shared in this roadmap show that the path forward is not only scientifically rich but has the potential to make wide and far reaching contributions to many societal challenges.

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The 2017 Plasma Roadmap: Low temperature plasma science and technology

The presence of a sample in the neutron field of a nuclear reactor creates a perturbation of the local neutron fluxes. In general, the interpretation of the sample activation due to thermal and epithermal neutrons requires the knowledge of two corrective parameters: the thermal neutron self-shielding factor, Gth, and the resonance neutron self-shielding factor, Gres. Thermal neutron self-shielding factors in different materials (Al, Au, Cd, Co, Cu, Eu, Gd, In, Ir, Mo, Ni, Pt, Pb, Rh, Sc, Sm and Ta) and different geometries (foils, wires, spheres and) have been calculated by using the MCNP code.

Nuclear Instruments and Methods

The impact-induced deposition of Al13 clusters with icosahedral structure on Ni(0 0 1) surface was studied by molecular dynamics (MD) simulation using Finnis–Sinclair potentials. The incident kinetic energy (Ein) ranged from 0.01 to 30 eV per atom. The structural and dynamical properties of Al clusters on Ni surfaces were found to be strongly dependent on the impact energy. At much lower energy, the Al cluster deposited on the surface as a bulk molecule. However, the original icosahedral structure was transformed to the fcc-like one due to the interaction and the structure mismatch between the Al cluster and Ni surface. With increasing the impinging energy, the cluster was deformed severely when it contacted the substrate, and then broken up due to dense collision cascade. The cluster atoms spread on the surface at last. When the impact energy was higher than 11 eV, the defects, such as Al substitutions and Ni ejections, were observed. The simulation indicated that there exists an optimum energy range, which is suitable for Al epitaxial growth in layer by layer. In addition, at higher impinging energy, the atomic exchange between Al and Ni atoms will be favourable to surface alloying.

Nuclear instruments and methods in physics research section B : beam interactions with materials and atoms

We present the grackle chemistry and cooling library for astrophysical simulations and models grackle provides a treatment of non-equilibrium primordial chemistry and cooling for H, D and He species, including H2 formation on dust grains; tabulated primordial and metal cooling; multiple ultraviolet background models; and support for radiation transfer and arbitrary heat sources The library has an easily implementable interface for simulation codes written in c, c++ and fortran as well as a python interface with added convenience functions for semi-analytical models As an open-source project, grackle provides a community resource for accessing and disseminating astrochemical data and numerical methods We present the full details of the core functionality, the simulation and python interfaces, testing infrastructure, performance and range of applicability grackle is a fully open-source project and new contributions are welcome

GRACKLE: a chemistry and cooling library for astrophysics

Cross section data have been compiled for electron collisions with hydrogen molecules based on 71 references. Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational, vibrational, and electronic states, dissociation, ionization, emission of radiation, and dissociative attachment. For each process, the recommended values of the cross section are presented for use. The literature has been surveyed through the end of 2006.

Cross Sections for Electron Collisions with Hydrogen Molecules

Cross section data are compiled from the literature for electron collisions with methane (CH4) molecules Cross sections are collected and reviewed for total scattering, elastic scattering, momentum transfer, excitations of rotational and vibrational states, dissociation, ionization, and dissociative attachment The data derived from swarm experiments are also considered For each of these processes, the recommended values of the cross sections are presented The literature has been surveyed through early 2014

Cross Sections for Electron Collisions with Methane

Spherical and nonspherical plasma‐screening effects are investigated on electron‐impact excitation of hydrogenic ions in weakly coupled plasmas. Semiclassical straight‐line trajectory method is used to describe the behavior of the projectile electron. Scaled 1s→2p−1 semiclassical excitation probabilities are obtained by the spherical and nonspherical Debye–Huckel interaction potentials. The plasma‐screening effect of the bound atomic wave functions in the transition probability obtained by the spherical Debye–Huckel model is found to be more effective than that in the transition probability obtained by the nonspherical Debye–Huckel model. The maximum position of the transition probability obtained by the nonspherical Debye–Huckel potential is more receded from the nucleus than that of transition probability obtained by the spherical Debye–Huckel potential.

Spherical versus nonspherical plasma‐screening effects on semiclassical electron–ion collisional excitations in weakly coupled plasmas

The demand for electron-impact cross sections has increased tremendously in recent years. There is, however, a special interest in such cross sections for hydrogen molecules and its isotopomers, HD and D2, because of their presence in tokamak edge plasmas, planetary atmospheres and at different astrophysical sites. This explains the need for having well validated sets of electron-impact cross sections for different processes. This work reviews the electron-scattering cross sections for elastic and inelastic processes at different electron energies for both these molecules. The elastic momentum transfer cross sections and inelastic cross sections for electron-impact rotational, vibrational and electronic excitation, emission, dissociation, ionization and dissociative electron attachment have been evaluated and well validated in this work wherever and whenever possible.

https://iopscience.iop.org/article/10.1088/0034-4885/73/11/116401/pdf

Electron-impact cross sections for deuterated hydrogen and deuterium molecules

Plasma-screening effects are investigated on semiclassical ionization probabilities for electron-impact ionization of hydrogenic ions in dense plasmas. The projectile - target interaction Hamiltonian is obtained by an appropriate form of the non-spherical Debye - Huckel model. Semiclassical straight-line trajectory method is applied to the projectile path in order to visualize the ionization probability in dense plasmas as a function of the impact parameter and Debye length. The final state of the ejected electron is represented by a plane wave solution normalized in the energy scale. The plasma-screening effect on the ionization probability is appreciably increased with increasing projectile energy. The maximum position of the ionization probability recedes from the nucleus as the projectile energy increases.

https://iopscience.iop.org/article/10.1088/0953-4075/29/15/024/pdf

Jung-Sik Yoon

Papers

Cross Sections for Electron Collisions with Hydrogen Molecules

Cross Sections for Electron Collisions with Methane

Spherical versus nonspherical plasma‐screening effects on semiclassical electron–ion collisional excitations in weakly coupled plasmas

Electron-impact cross sections for deuterated hydrogen and deuterium molecules

Plasma-screening effects on semiclassical ionization probabilities for the electron-impact ionization of hydrogenic ions in dense plasmas