The major increase in discharge duration and plasma energy in a next step DT fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety and performance. Erosion will increase to a scale of several centimetres from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma facing components. Controlling plasma-wall interactions is critical to achieving high performance in present day tokamaks, and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena stimulated an internationally co-ordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor project (ITER), and significant progress has been made in better understanding these issues. The paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next step fusion reactors. Two main topical groups of interaction are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation and (ii) tritium retention and removal. The use of modelling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R&D avenues for their resolution are presented.

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Plasma{material interactions in current tokamaks and their implications for next step fusion reactors

This document is the user`s manual for the third-generation CHEMKIN package. CHEMKIN is a software package whose purpose is to facilitate the formation, solution, and interpretation of problems involving elementary gas-phase chemical kinetics. It provides a flexible and powerful tool for incorporating complex chemical kinetics into simulations of fluid dynamics. The package consists of two major software components: an Interpreter and a Gas-Phase Subroutine Library. The Interpreter is a program that reads a symbolic description of an elementary, user-specified chemical reaction mechanism. One output from the Interpreter is a data file that forms a link to the Gas-Phase Subroutine Library. This library is a collection of about 100 highly modular FORTRAN subroutines that may be called to return information on equations of state, thermodynamic properties, and chemical production rates. CHEMKIN-III includes capabilities for treating multi-fluid plasma systems, that are not in thermal equilibrium. These new capabilities allow researchers to describe chemistry systems that are characterized by more than one temperature, in which reactions may depend on temperatures associated with different species; i.e. reactions may be driven by collisions with electrons, ions, or charge-neutral species. These new features have been implemented in such a way as to require little or no changes to CHEMKIN implementation for systems in thermal equilibrium, where all species share the same gas temperature. CHEMKIN-III now has the capability to handle weakly ionized plasma chemistry, especially for application related to advanced semiconductor processing.

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CHEMKIN-III: A FORTRAN chemical kinetics package for the analysis of gas-phase chemical and plasma kinetics

Complex (dusty) plasmas: current status, open issues, perspectives

Progress, since the ITER Physics Basis publication (ITER Physics Basis Editors et al 1999 Nucl. Fusion 39 2137–2664), in understanding the processes that will determine the properties of the plasma edge and its interaction with material elements in ITER is described. Experimental areas where significant progress has taken place are energy transport in the scrape-off layer (SOL) in particular of the anomalous transport scaling, particle transport in the SOL that plays a major role in the interaction of diverted plasmas with the main-chamber material elements, edge localized mode (ELM) energy deposition on material elements and the transport mechanism for the ELM energy from the main plasma to the plasma facing components, the physics of plasma detachment and neutral dynamics including the edge density profile structure and the control of plasma particle content and He removal, the erosion of low- and high-Z materials in fusion devices, their transport to the core plasma and their migration at the plasma edge including the formation of mixed materials, the processes determining the size and location of the retention of tritium in fusion devices and methods to remove it and the processes determining the efficiency of the various fuelling methods as well as their development towards the ITER requirements. This experimental progress has been accompanied by the development of modelling tools for the physical processes at the edge plasma and plasma–materials interaction and the further validation of these models by comparing their predictions with the new experimental results. Progress in the modelling development and validation has been mostly concentrated in the following areas: refinement in the predictions for ITER with plasma edge modelling codes by inclusion of detailed geometrical features of the divertor and the introduction of physical effects, which can play a major role in determining the divertor parameters at the divertor for ITER conditions such as hydrogen radiation transport and neutral–neutral collisions, modelling of the ion orbits at the plasma edge, which can play a role in determining power deposition at the divertor target, models for plasma–materials and plasma dynamics interaction during ELMs and disruptions, models for the transport of impurities at the plasma edge to describe the core contamination by impurities and the migration of eroded materials at the edge plasma and its associated tritium retention and models for the turbulent processes that determine the anomalous transport of energy and particles across the SOL. The implications for the expected performance of the reference regimes in ITER, the operation of the ITER device and the lifetime of the plasma facing materials are discussed.

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Chapter 4: Power and particle control

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

Elementary Processes in Hydrogen-Helium Plasmas

Basic Properties of Fusion Edge Plasmas and Role of Atomic and Molecular Processes (R.K. Janev). Spectroscopic Processes and Data for Fusion Edge Plasmas (W.L. Wiese). Elastic and Excitation Electron Collisions with Atoms (S. Trajmar, I. Kanik). Electron Impact Ionization of Plasma Edge Atoms (T. Mark). Electron-Ion Recombination Processes in Plasmas (Y. Hahn). Excitation of Atomic Ions by Electron Impact (S.S. Tayal et al.). Ionization of Atomic Ions by Electron Impact (D. Defrance et al.). The Dependence of Electron Impact Excitation and Ionization Cross Sections of H2 and D2 Molecules on Vibrational Quantum Number (M. Capitelli, R. Celiberto). Electronmolecular Ion Collision Processes (J.B.A. Mitchell). Energy and Angular Distributions of Secondary Electrons Produced by Electronimpact Ionization (Y.K. Kim). Elastic and Related Cross Sections for Low Energy Collisions among Hydrogen and Helium Ions, Neutrals, and Isotopes (D.R. Schultz et al.). Rearrangement Processes Involving Hydrogen and Helium Atoms and Ions (F. Brouillard, X. Urbain). Reactive Ionmolecule Collisions Involving Hydrogen and Helium (F. Linder et al.). 3 additional articles. Index.

Atomic and molecular processes in fusion edge plasmas

State-selective electron capture in atom-highly charged ion collisions

Cross section data for electron-impact inelastic processes of vibrationally excited molecules of hydrogen and its isotopes

1. Introduction.- 1.1 General Overview.- 1.2 Basic Features of Highly Charged Ions and Their Interactions.- 1.3 Highly Charged Ions in Astrophysics.- 1.4 Highly Charged Ions in Controlled Thermonuclear Fusion Research.- 1.5 Highly Charged Ions in Accelerator-Based Physics and Other Research Fields.- 1.6 Scope of the Book.- 2. Structure and Spectra of Highly Charged Ions.- 2.1 General Properties of the Spectra.- 2.2 Satellites of the Spectral Lines.- 2.3 Classification of the States and Spectral Lines of Multiply Charged Ions.- 2.4 Relativistic and Radiative Effects.- 2.5 Decay of Excited Ionic States. Radiation and Autoionization.- 2.6 Static and Dynamic Dipole Polarizabilities of Multiply Charged Ions.- 2.6.1 General Remarks.- 2.6.2 Static Polarizability.- 2.6.3 Dynamic Polarizability.- 3. Radiative Processes in the Continuous Spectrum.- 3.1 Bremsstrahlung.- 3.2 Photoionization and Photorecombination.- 3.3 Dielectronic Recombination.- 3.3.1 Resonance Character of the Process.- 3.3.2 Theory and Experiment.- 3.4 Autoionization.- 4. Electron Collisions with Highly Charged Ions: General Theory and Excitation Processes.- 4.1 Introductory Remarks.- 4.2 Basic Equations.- 4.3 Effective-Range Theory for Attractive Coulomb Field.- 4.4 Quantum Defect Method. The Seaton Theory.- 4.5 Correct Asymptotic Expansion. Influence of Dielectronic Recombination.- 4.5.1 Radial Green's Function.- 4.5.2 Solution of Integral Equations.- 4.5.3 T Matrix and Cross Sections.- 4.5.4 Radiative Decay of Resonances.- 4.6 Results of Calculations and Experimental Data.- 5. Electron-Impact Ionization of Highly Charged Ions.- 5.1 One-Electron Ionization. General Remarks.- 5.2 Exchange Effects in Ionization. The Peterkop Theory.- 5.3 Threshold Behaviour of the Cross Section.- 5.4 Quantum-Mechanical Methods for Ionization Cross Section Calculations.- 5.5 Classical and Semi-Empirical Formulae.- 5.6 Excitation-Autoionization.- 5.7 Experimental Data and Comparison with Theoretical Calculations.- 5.8 Analytic Approximations for the Quantum-Mechanical Cross Sections.- 6. Collisions of Atoms with Highly Charged Ions: General Theoretical Description.- 6.1 Two-Coulomb-Centre Problem.- 6.1.1 The Eigenvalue Problem.- 6.1.2 Correlation Rules and Pseudocrossings.- 6.1.3 Energy Splitting at a Pseudocrossing.- 6.1.4 Algorithms for Solving the Eigenvalue Problem for the (Z1, e, Z2) System.- 6.1.5 Application of the Two-Centre Problem to Many-Electron Diatomic Molecules: Molecular Orbital Model.- 6.2 Close-Coupling Methods.- 6.2.1 General Formulation of the Close-Coupling Methods.- 6.2.2 Molecular-Orbital Close-Coupling (MO - CC) Methods.- 6.2.3 Atomic-Orbital Close-Coupling (AO - CC) and Related Methods.- 6.2.4 Two-State Close-Coupling Models and Approximations.- 6.3 Perturbation Methods.- 6.3.1 Formal Theory of Atomic Reactions.- 6.3.2 Born Series.- 6.3.3 Distorted-Wave Method.- 6.3.4 Perturbation Treatment of Close-Coupled Equations.- 6.3.5 Second-Order and Related Approximations.- 6.4 Classical Descriptions.- 6.4.1 Binary-Encounter Approximation (BEA).- 6.4.2 Classical Trajectory Monte Carlo (CTMC) Method.- 7. Collisions of Atoms (Ions, Molecules) with Highly Charged Ions: Charge-Transfer Processes.- 7.1 General Considerations.- 7.2 Charge Exchange at Low Energies.- 7.2.1 Decay Models.- 7.2.2 Multichannel Landau-Zener Model.- 7.2.3 Molecular-Orbital Close-Coupling Calculations.- 7.2.4 Analytic Treatment of Diabatic MO - CC Equations.- 7.3 Electron Capture at Intermediate Energies.- 7.3.1 AO-CC Method: Numerical Calculations.- 7.3.2 Approximate Treatments of Coupled-Channel Equations.- 7.3.3 Classical Treatments.- 7.4 Electron Capture at High Energies.- 7.4.1 The Brinkman-Kramers Approximation and Its Extensions.- 7.4.2 Higher-Order Approximations.- 7.4.3 Electron Capture into Continuum States.- 7.5 General Features of Single-Charge-Transfer Cross Sections.- 7.5.1 Scaling Laws for the Total Single-Charge-Transfer Cross Section.- 7.5.2 Final-State Distributions of Captured Electrons.- 7.5.3 Z-Oscillations of the Total Cross Sections.- 7.6 Single-Charge Transfer in Ion-Ion and Ion-Molecule Collisions.- 7.6.1 Ion-Ion Charge Exchange.- 7.6.2 Ion-Molecule Charge Exchange.- 7.7 Multiple-Charge Transfer.- 7.7.1 Two-Electron-Capture Processes.- 7.7.2 Multi-Electron-Capture Processes.- 8. Collisions of Atoms (Ions) with Highly Charged Ions: Excitation and Ionization.- 8.1 Basic Electron Transition Mechanisms.- 8.2 Excitation Processes.- 8.2.1 Close-Coupling Treatments.- 8.2.2 UDWA Treatment.- 8.2.3 Perturbation Theory and VPS Approximation.- 8.2.4 Excitation in Ion-Ion Collisions.- 8.3 Single-Electron Ionization.- 8.3.1 Perturbation Treatments.- 8.3.2 DACC Theory for Ionization.- 8.3.3 UDWA Calculations.- 8.3.4 Classical Models.- 8.3.5 Higher-Order High-Energy Approximations.- 8.3.6 Ion-Ion and Ion-Molecule Ionization.- 8.3.7 Scaling Laws for Single-Electron Ionization.- 8.3.8 Direct Multiple-Ionization.- 8.4 Electron Loss and Stripping Processes.- 8.4.1 The Keldysh Quasi-Classical Method.- 8.4.2 Classical Treatments.- 8.4.3 Stripping Reactions.- 9. Auger, Inner-Shell and Related Processes.- 9.1 Collisional Auger Processes Involving Outer Shells.- 9.1.1 Capture-Excitation.- 9.1.2 Capture-Ionization.- 9.1.3 Multiple Transfer Ionization.- 9.2 Inner-Shell Processes.- 9.2.1 Basic Electron Transition Mechanisms.- 9.2.2 K- and L-Shell Excitations.- 9.2.3 Vacancy Sharing.- 9.2.4 Correlated Electron Transitions in Vacancy Production and Decay.- 9.3 Some Aspects of Quasi-Molecule and Quasi-Atom Formation in Heavy Ion Collisions.- 9.3.1 Quasi-Molecular X-Ray Radiation.- 9.3.2 Positron Emission.- 10. Rate Coefficients of Elementary Processes.- 10.1 Energy (Velocity) Distribution Function.- 10.2 Electron-Impact Excitation.- 10.3 Electron-Impact Ionization.- 10.4 Photorecombination.- 10.5 Dielectronic Recombination.- 10.6 Charge Transfer.- References.

Ratko K. Janev

Papers

Elementary Processes in Hydrogen-Helium Plasmas

Atomic and molecular processes in fusion edge plasmas

State-selective electron capture in atom-highly charged ion collisions

Cross section data for electron-impact inelastic processes of vibrationally excited molecules of hydrogen and its isotopes

Physics of Highly Charged Ions