A summary is given of the present status of research on plasma-surface interactions in tokamaks. Three groups of important interactions are considered: recycling of the principal ion species, usually hydrogen or deuterium; the release and effect of low-Z contaminants; and the release and effect of high-Z contaminants. In each case the basic physical processes are reviewed and the relevant data from particlebeam measurements are summarized. Emphasis is given to discussing the effect of the various surface interactions in present-day tokamak discharges and in future fusion reactors. Surface studies in tokamaks are reviewed and methods of controlling the surface interactions and their effects are considered.

Plasma-surface interactions in tokamaks

The objective of this article is to review the effects of high density cascades in solids. Such cascades can be separated into those occurring in which “high density” refers to either the density of atomic collision events or to the density of ionization. Both types of cascade are discussed with reference to their effects in the bulk (i.e. damage production and inert gas detrapping) and on the surface properties (i.e. sputtering, secondary ion and electron emission). The appropriate experimental data are reviewed and discussed in relation to the various proposed spike models; i.e. displacement, thermal, plasticity and ionization spikes.

High density cascade effects

After a brief outline of the present sputtering theory for a random solid, recent results of the sputtering yieldS for polycrystalline targets are discussed, in particular in view of the influence of the projectile mass and the bombarding angle. The angle dependence ofS at low bombarding energies, and results on the angular distribution of sputtered particles for oblique ion incidence point out necessary modifications of present sputtering theories with respect to the anisotropy of the collision cascades in the solid and the influence of the target surface. The energy distribution of the neutral particles ejected along the target normals is related to the theoretically predictedE
 −2-distribution of low energy recoils in the Recent mass spectrometric studies of postionized sputtered neutrals are discussed in view of the formation of sputtered molecules and the application of sputtered neutral mass spectroscopy for surface analysis. Finally, the paper deals with ion-induced surface effects on non-elementary sputtering targets, and the protracted removal of foreign atoms from a matrix.

Sputtering—a review of some recent experimental and theoretical aspects

Ion beam induced surface and interface engineering

A review of particle-solid processes pertinent to modelling plasma-wall interactions is presented, and sets of recommended data are given. Analytic formulas are used where possible; otherwise, data are presented in the form of tables and graphs. The incident particles considered are e−, H, D, T, He, C, O, and selfions. The materials include the metals aluminum, beryllium, copper, molybdenum, stainless steel, titanium, and tungsten and the nonmetals carbon and TiC. The processes covered are light ion reflection, hydrogen and helium trapping and detrapping, desorption, evaporation, sputtering, chemical effects in sputtering, blistering caused by implantation of helium and hydrogen, secondary electron emission by electrons and particles, and arcing.

Data Compendium for Plasma-Surface Interactions

I. Implantation Modification of Superconductivity.- Superconductivity of Palladium and Pd-Alloys Charged with H or D by Ion Implantation at Helium Temperatures.- Ion Implantation in Superconducting Thin Films.- Ion Implantation in Superconducting Niobium Thin Films.- Superconducting Properties of the Dilute Magnetic Alloys Pb-Mn, Sn-Mn and Hg-Mn Obtained by Ion Implantation.- Ion Irradiation and Flux Pinning in Type II Superconductors.- II. Ion Induced Surface Reactions.- The Use of Ion Beams in Corrosion Science.- The Effects of Ion Bombardment on the Thin Film Oxidation Behavior of Zircaloy-4 and Zr-1.0 Nb.- Ion Implantation and Backscattering from Oxidized Single-Crystal Copper.- Movement of Ions During the Anodic Oxidation of Aluminum.- Friction and Wear of Ion Implanted Metals.- III. Thin Films and Interfaces.- Ion Beam Studies of Metal-Metal and Metal-Semiconductor Reactions.- Rutherford Scattering Studies of Diffusion in Thin Multilayer Metal Films.- Analysis of Compound Formation in Au-Al Thin Films.- Thin Film Interdiffusion of Chromium and Copper.- Ion Backscattering Study of WSi2 Layer Growth in Sputtered W Contacts on Silicon.- Reactions of Thin Metal Films with Si or SiO2 Substrates.- Ion Beam Induced Intermixing in the Pd/Si System.- IV. Alloying and Migration in High Fluence Implants.- Precipitation During Ion Bombardment of Metals.- Radiation Damage and Ion Behavior in Ion Implanted Vanadium and Nickel Single Crystals.- Sb-Implanted A? Studied by Ion Backscattering and Electron Microscopy.- The Changes in Electrical Properties of Tantalum Thin Films Following Ion Bombardment.- Implantation and Diffusion of Au in Be: Behavior During Annealing of a Low-Solubility Implant.- Anomalous Room Temperature Diffusion of Ion-Injected Ni in Zn Targets.- Study of Li-6 Implanted into Niobium.- V. Implanted Atom Location.- Lattice Location of Impurities Implanted into Metals.- High Substitutional Fractions in Cold Implantations of Xe and Te in Iron as Shown by Mossbauer Effect Measurements.- Valence Determination and Lattice Location via Mossbauer Spectroscopy of Gd151 Implanted into Iron.- Combined Lattice Location and Hyperfine Field Study of Yb Implanted into Fe.- Effect of Radiation Damage on Lattice Location and Hyperfine Interactions of Impurities Implanted in Iron.- Determination of Unique Site Population in Various In Implanted Non-Cubic Metals using Angular Correlations and the Nuclear Electric Quadrupole Interaction.- The Location of Displaced Manganese and Silver Atoms in Irradiated Aluminum Crystals by Backscattering.- Lattice Location Studies of 2D and 3He in W.- Location of He Atoms in a Metal Vacancy.- Simulation of Inert Gas Interstitial Atoms in Tungsten.- VI. Ion Lattice Damage.- Ion Damage Effects in Metals as Studied by Transmission Electron Microscopy.- Transmission Electron Microscopy Study of Implantation Induced Defects in Gold.- Transmission Electron Microscope Studies of Defect Clusters in Aluminium Irradiated with Gold Ions.- Dechanneling from Damage Clusters in Heavy Ion Irradiated Gold.- Heavy Ion Damage in Thin Metal Films.- Formation of Interstitial Agglomerates and Gas Bubbles in Cubic Metals Irradiated with 5 keV Argon Ions.- Observation of Ion Bombardment Damage in a Ni (100) Crystal by Helium Ion Injection.- VII. Ion Implanted Gas Buildup.- Helium Implantation Effects in Vanadium and Niobium.- Effect of He+ and D+ Ion Beam Flux on Blister Formation in Niobium and Vanadium.- Depth Distribution and Migration of Implanted Helium in Metal Foils using Proton Backscattering.- Blistering of Niobium due to Low Energy Helium Ion Bombardment Investigated by Rutherford Backscattering.- Radiation Damage and Gas Diffusion in Molybdenum Under Deuteron Bombardment.- Radiation Blistering After H+, D+ and He+ Ion Implantation into Surfaces of Stainless Steel, Mo, and Be.- VIII. Voids and Implantation Simulation of Neutron Damage.- A Review of Ion Simulation of High Temperature Neutron Damage and Void Formation.- Ion Radiation Damage.- 4 MeV Iron Atom Bombardment of Iron.- Flux (Dose Rate) Effects for 2.8 MeV 58Ni Irradiations of Pure Ni.- Heavy Ion-Induced Void Formation in Pure Nickel.- The Temperature Dependence of Irradiation Induced Void Swelling in 20% Cold Worked Type 316 Stainless Steel Irradiated with 5 MeV Nickel Ions.- Author Index.

Applications of Ion Beams to Metals

Applications of ion beams to metals. International conference held in Albuquerque, New Mexico, October 2--4, 1973

Radiation damage and blister formation in a Nb single crystal due to room temperature bombardment with 2–4 keV He ions has been investigated by Rutherford backscattering in double aligned technique ( /(111) and / ) of 150 keV protons. By this technique it is possible to observe in situ the development of blisters. The critical ion dose for blister formation is about 1017 He+ /cm2 increasing with energy. It is higher for He bombardment in aligned than in random directions. The mean thickness of the cover of the blisters increases from 234A at 2 keV to 420A at 4 keV He bombardment in random direction. The average blister size as measured in the SEM was 600A at 2 keV and 1400A at 4 keV random bombardment. In aligned bombardment it increases by roughly a factor of 2. The results of our backscattering measurements before the appearance of blisters may be interpreted by the assumption that small Helium bubbles are formed at the penetration depth of the He ions. The measured penetration depth is considerably larger than predicted by theory (Schioftt).

F.L. Vook

Papers

Applications of Ion Beams to Metals

Applications of ion beams to metals. International conference held in Albuquerque, New Mexico, October 2--4, 1973

Blistering of niobium due to low energy helium ion bombardment investigated by Rutherford backscattering