We present a description of the interaction of CF₃⁺ ions with a Ag(111) surface. The angular and energy distributions of the scattered ions (negative and positive) are measured for incident beam energies ranging from 100 to 500 eV. Comparison is made with CF₃⁺ scattering measurements from HOPG. The results can be explained using a combination of electronic and mechanical effects. We propose a sequence of charge exchange and collision-induced processes that are consistent with the measured data. The dominant electronic process is a dissociative neutralization of the CF₃⁺ prior to the surface collision. There is also a non-dissociative neutralization channel, which allows some of the parent molecules to survive the surface interaction. The incoming molecules can be further dissociated by internal energy uptake due to the impulsive collision with the surface.

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We discuss charged particle emissions induced by low energy ion impact on non-metallic surfaces. It has been shown that the secondary electron emission yields (γ^-) observed in non-metallic targets are 2 - 3 times larger than those for metallic targets. As special phenomena in non-metallic targets, the Coulomb explosion phenomena, the incident ion flux dependence of γ^- and the target temperature dependence of γ^- are described. Furthermore, it is found that the secondary ion emission yields from non-metallic targets are larger than those from metallic targets. It is also shown that the key mechanisms responsible for ion emissions from non-metallic surfaces induced by low energy ion impact are very different from those for metal targets.

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This paper describes the similarities and differences between physical sputtering and secondary electron emission from solids under ion bombardment. Emphasis is placed on the energy and angular distributions of emitted particles and particle emission statistics, as well as on total particle yield. The sputtering yield and secondary electron yield are strongly related to the nuclear stopping power and electronic stopping power of the solids for incident ions, respectively, whereas the energy distributions of sputtered atoms and secondary electrons are less influenced by these ions. Due to “collision cascade” and “electron cascade” before these atoms and electrons escape from the surface, both the energy distributions are similar to each other. However, the angular distribution of sputtered atoms shows under- and over-cosine distribution for low-energy and high-energy ions, respectively, whereas the angular distribution of secondary electrons is close to the cosine distribution, which results from the isotropic momentum distribution of secondary electrons inside the solids. For both, the statistical distribution for emission probabilities deviates from the Poission distribution in most cases.

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Plasma etching is an indispensable processing technique in the fabrication of modern microelectronic devices. The processing is essentially the result of physical and chemical processes of enormous complexity that occur in the gas phase and at the gas-solid interface. Nowadays, as integrated circuit device dimensions continue to be scaled down, increasingly strict requirements are being imposed on plasma etching technology, which in turn requires a better understanding of the physics and chemistry underlying the processing. This paper reviews recent studies of plasma-surface interactions in plasma etching environments, including gas-phase kinetics, plasma-wall interactions, and plasma-surface interactions in large open fields and also in microstructural features. Emphasis is placed on silicon etching in low-pressure, high-density chlorine-containing plasmas, which relies primarily on ion-assisted or ion-enhanced surface reaction processes during simultaneous exposure of neutral reactants and energetic ions.

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In this report, thin film deposition technologies using plasma-enhanced chemical vapor depositions (PECVD) are reviewed. First, the deposition kinetics of hydrogenated amorphous silicon are described. Secondly, various kinds of PECVD are explained and their use in the application of thin films to display devices such as active matrix liquid crystal displays and field emission displays are described.

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This paper describes PBII (Plasma-Based Ion Implantation). In PBII a target material is immersed in a plasma and pulsed high voltage with a negative polarity is directly applied to the target with three-dimensional shapes for realizing uniform ion implantation. Gaseous and non-gaseous plasmas are employed. When the pulsed voltage is applied to the target material, an ion sheath is formed around the target material and ions are implanted into the target material. The ion motion is described using the Child-Langmuir theory. The conditions for conformal ion implantation into the target material are discussed in terms of time evolution of the sheath expansion into the plasma. Pulsed plasma is seen as a method to establish conformal implantation. Finally, the application of PBII is described.

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Edge plasma physics and atomic-molecular processes relating to plasma heat flow to material surfaces are discussed. The local heat flow was found to be enhanced by a thermal contraction induced by cross-field potential variation in a plasma, resulting in hot spot formation on the plasma-facing materials due to nonlinear thermal bifurcation induced by thermoelectron emission. Also examined is the recombination enhancement due to the vibrationally excited hydrogen molecule generated from material surfaces in detached plasma with molecular activated recombination.

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The erosion processes of plasma facing materials are reviewed. Chemical sputtering and radiation enhanced sublimation of graphite materials are explained including elementary processes and modeling. Several important phenomena affecting the erosion of plasma facing materials such as disruption, materials mixing, and prompt redeposion are briefly overviewed.

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Most of magnetically confined fusion devices have installed carbon as the main plasma facing material (PFM). This carbon is typically used in combination with low-Z or high-Z materials to reduce/compensate the high erosion rate caused by high heat/particle loadings. While the use of carbon has resulted in good plasma performance, its use has also generated new problems, one of which is the formation of mixed material layers consisting mainly of the constituents of the PFMs, often including sizable quantities of hydrogen isotopes from the plasma. In this paper, the present status and current objectives of the use of carbon first-walls are discussed from the viewpoint of fuel recycling and inventory.

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Wall conditioning techniques for fusion wall surfaces are surveyed. Focused on the wall conditioing by low-Z film coating, its effect on the reduction of impurity and on the hydrogen recycling is described. Guidelines we suggested for uniform coating of the wall in boronization, which has been shown to aid in the suppression of the impurities in wall materials. The reduction of the oxygen impurity by low-Z film conditioning, such as boronization or lithium conditioning, is described. The reduction of the hydrogen retention by helium discharge conditioning is also mentioned.

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General formulas for gas-driven permeation, plasma-driven permeation and simultaneous gas- and plasma-driven permeation have been derived by a circuit analogy, in which permeation resistance and permeation potential are newly defined for both diffusion in the bulk and recombination on the surface and the gradient of permeation potential against permeation resistance is considered to be the general driving force for tritium permeation through a laminate. The formula is applied to the assessment of tritium permeation and inventory in ITER divertor.

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Erosion of boron exposed to deuterium plasmas containing carbon impurity is investigated using a Monte Carlo simulation model for ion-solid interactions which takes dynamic composition change in the surface layer into account. The calculated results are compared with an erosion experiment of a boronized graphite test piece in TEXTOR-94. The implantation of carbon impurities strongly decreases the boron sputtering yield as a result of the formation of a thick carbon containing layer near the surface. These calculations can explain the experimental observations of surface erosion near the plasma edge and deposition of carbon at the surface location far from it. However, non-linear change of the observed thickness of boronized layer with time is not reproduced by the simulation. Furthermore, the carbon depth profile observed after the plasma exposure broadens inside the layer, deeper than the calculated profile.

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In Plasma Based Ion Implantation (PBII) using a titanium arc of DC 70 A with a pulse voltage of −10 to −40 kV/20 μs, titanium nitride (TiN) films were coated on a silicon substrate (p-type, (100)) and titanium ions were simultaneously implanted. XPS results indicate that the implanted layer is formed inside the silicon substrate. The thickness of the implanted layer remains constant regardless of the tilt angle of the substrate, whereas deposition thickness varies as the angle is changed. XRD patterns show that the crystal orientation of the film produced by PBII differs from that produced using DC bias. A pulse voltage of −20 to −40 kV with a nitrogen pressure of 0.27 Pa forms a film of strongly (200) preferred orientation, while a DC bias of −500 V (111) and (220) preferred orientation.

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Solving the problem of plasma wall interaction is important for developing the fusion reactor. One of the problems involved with this interaction is plasma driven permeation (PDP), the phenomenon of large hydrogen permeation by plasma. This report focuses on previous studies of PDP, and reviews the abstracts of many experimental and theoretical works regarding PDP. In addition, this report introduces our original work on low temperature plasma driven permeation. In our work, ECR and RF heating plasma devices and various kinds of metal membranes were employed. Also researched were the dependencies of membrane thickness, temperature, and surface conditions on PDP. The incident hydrogen flux rate, which is little known in PDP experiments using a plasma discharging device, was estimated by calculating plasma composition. The mechanism of low temperature PDP was investigated and shown conceptually.

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Matrix Inversion (MI) method is developed in order to estimate the neoclassical ion thermal diffusivity, χ_NC, correctly. In the MI method, effects of impurity on χ_NC are treated self-consistently and no approximation on the friction and the viscosity matrix elements is carried out. The comparison of χ_NC value between the MI method and the Chang-Hinton’s (CH) formula shows that the CH formula over-estimates χ_NC value twice as large as that of MI method for typical JT-60U plasmas. The different dependence of χ_NC on the inverse aspect ratio, ε, the effective charge number, Z_eff, and the normalized ion collisionality, ν_*i, between the MI method and the CH formula is presented. The radial electric field. E_r, is estimated from the momentum and the heat momentum balance equations parallel to the magnetic field. Profiles of E_r are compared between the two types of improved core confinement plasmas with internal transport barrier (ITB) in JT-60U, the “parabolic type ITB” and the “box type ITB”. In the box type ITB, the experimentally estimated thermal diffusivity. χ^exp, decreases in the core region. However, the E_r shear is not so strong. In the box type ITB, a strong E_r shear appears inside the ITB layer and the χ^exp value decreases drastically to the level of χ_NC. The E×B shearing rate becomes almost the same as the linear growth rate of the drift microinstability inside the ITB layer of the box type ITB.

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Several years ago a new concept called “fast ignition” was introduced for inertial confinement fusion (ICF). The concept proposes to use an ultra-intense (Peta watt) short (psec) laser pulse to ignite a highly compressed fuel core within the core disassembly time. Since then, Japan, England, France, Italy, Germany, Spain, Russia, Spain and USA started intensive studies on ultrahigh intensity laser plasma interactions. We report on our most recent experimental and theoretical studies on fast ignitor related research at the Institute of Laser Engineering, Osaka University.

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Behavior of lithium deposited on graphite is investigated by using a laboratory experimental apparatus, focusing on the intercalation of lithium in the graphite and physical sputtering of lithium-intercalated graphite. It Is found that the lithium can easily diffuse into the graphite bulk even at room temperature, and that the diffusion of lithium is enhanced by heating the graphite. Suppression of physical sputtering of graphite by lithium deposition is found by Auger depth measurement of sputtered species collected on substrates and by optical emission spectroscopy. It is also found that the suppression of graphite sputtering can be sustained in longer period due to intercalated lithium. Finally, general precautions to achieve the reproducible lithium effect in fusion machines are described.

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A new-type laboratory experiment of magnetic reconnection has been developed at TS device (University of Tokyo) using two merging spheromaks and tokamaks. It enables us to form spontaneously closed current-sheet in Magnetohydrodynamic regime, eliminating boundary problems of the previous open-type reconnection experiments. The reconnection speed was observed to increase with increasing external force to compress the sheet (driven reconnection) and with decreasing the third magnetic field component B_X Parallel to the sheet (three-component reconnection). The most probable cause of these effects is the anomalous resistivity of the sheet that appears when the sheet width is compressed shorter than its ion gyro-radius. Ion acceleration and following direct ion heating of magnetic reconnection were also directly measured for the first time. The ion heating as well as the anomalous resistivity is suppressed with increasing B_X, in agreement with the high T_i(>T_e) characteristics of RFPs With small B_X and the T_i ≈T_e ones of tokamaks with large B_X.

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In the ultra-low-aspect-ratio tokamak, neoclassical viscosity plays a role to enhance the neoclassical transport such as bootstrap current and ion thermal conductivity in the Pfirsch-Schlüter regime. The geometrical factor <(n ∇B)²> for calculating the viscosity [K.C. Shaing et al., Phys. Plasmas 3, 965 (1996)] shows divergent tendency for assumed sequences of numerical MHD equilibria when the aspect ratio is reduced to 1.05, where n=B/B and B is the equilibrium magnetic field.

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