The interaction of plasma with the walls has been one of the critical issues in the development of fusion energy research. On the one hand, plasma induced erosion can seriously limit the lifetime of the wall components, while, on the other hand, eroded particles can be transported into the core plasma where they lead to dilution of the fusion plasma and to energy losses due to radiation. Low-Z wall materials induce only small radiation losses in the plasma core but suffer from large physical sputtering rates. Carbon based materials in addition suffer from chemically induced erosion. High-Z wall materials show significantly smaller erosion but lead to large radiation losses. One of the main goals of present plasma-wall studies is to find a special choice of wall materials for steady state plasma scenarios that will provide an optimum with respect to fuel dilution, radiation losses, wall lifetime and fuel inventory in the walls. To obtain a better understanding of the processes and to estimate the plasma-wall interaction behaviour in future fusion devices the 3-D Monte Carlo code ERO-TEXTOR, based originally on the ERO code, has been developed. It models the plasmawall interaction and transport processes in the vicinity of a surface positioned in the boundary layer of TEXTOR. The main aim is to simulate the erosion and redeposition behaviour of different wall materials under various plasma conditions and to compare this with experimental results. This contribution describes the main features of the ERO-TEXTOR code and gives some examples of simulation calculations to illustrate the application of the code.

Dust can play an important role in fusion devices. Various mechanisms for dust production are discussed including the possible growth of particulates during the fusion plasma discharge itself. Samples of dust from TEXTOR-94 are analysed by scanning electron microscopy. The particle size ranges from millimetres down to <100 nm. The morphology of the smallest particles suggests their plasma-induced growth. Part of the dust is ferromagnetic. The impact of dust particles on safety, plasma operations and performance is addressed.

The progressive liquid-phase layer-by-layer (LbL) growth of anisotropic multicomponent layer-based porous coordination polymers (PCPs) of the general formula [M(L)(P)(0.5)] (M: Cu(2+), Zn(2+); L: dicarboxylate linker; P: dinitrogen pillar ligand) was investigated by using either pyridyl- or carboxyl-terminated self-assembled monolayers (SAMs) on gold substrates as templates. It was found that the deposition of smooth, highly crystalline, and oriented multilayer films of these PCPs depends on the conditions at the early growth cycles. In the case of a two-step process with an equimolar mixture of L and P, growth along the [001] direction is strongly preferred. However, employing a three-step scheme with full separation of all components allows deposition along the [100] direction on carboxyl-terminated SAMs. Interestingly, the growth of additional layers on top of previously grown oriented seeding layers proved to be insensitive to the particular growth scheme and full retention of the initial orientation, either along the [001] or [100] direction, was observed. This homo- and heteroepitaxial LbL growth allows full control over the orientation and the layer sequence, including introduction of functionalized linkers and pillars.

A global model of the self-pulsing regime of micro-hollow cathode discharges J. Appl. Phys. 111, 053305 (2012) On the accuracy and reliability of different fluid models of the direct current glow discharge Phys. Plasmas 19, 033502 (2012) Particle-in-cell simulations of hollow cathode enhanced capacitively coupled radio frequency discharges Phys. Plasmas 19, 023508 (2012) Optical visualization and electrical characterization of fast-rising pulsed dielectric barrier discharge for airflow control applications J. Appl. Phys. 111, 033303 (2012) Self-pulsing operating mode of hollow cathode discharge in noble gas

Proper wall conditioning has turned out to be an essential element for achieving the highest possible plasma performance in present day fusion devices. The main issues are controlling the generation of plasma impurities, liberated by plasma-surface interactions, and controlling the recycling hydrogenic fluxes. The underlying mechanisms are discussed in this paper. The paper presents a review of the different wall conditioning methods. It focuses on low-Z wall coatings (beryllium evaporation, boronization, siliconization, lithium pellet injection) and on helium glow discharge cleaning and assesses their effects on fusion plasmas. New wall conditioning concepts, compatible with steady-state magnetic fields, are discussed in view of future large devices with superconducting coils.