[en] Short communication

No abstract available

[en] Effects of parallel and poloidal flows, as well as the flow shear, on the resistive wall mode (RWM) instability have been numerically investigated in toroidally rotating plasmas, utilizing a recently updated version of the MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681). A significant difference between these flows is that the background toroidal flow frequency is symmetric with respect to the poloidal angle, whilst both the poloidal and toroidal projections of the additional parallel flow are functions of both the plasma minor radius and poloidal angle. It is found that the stability of the RWM is hardly modified by the parallel flow, as a consequence of cancellation of the stabilizing effect provided by the poloidal projection of the parallel flow from one side, and the destabilizing effect provided by the toroidal projection from the other side. The destabilizing effect of the toroidal projection comes predominantly from the m  =  1 poloidal Fourier harmonic of the flow contribution. The shear of the parallel flow is found to generally weaken the stabilization/destabilization effect on the RWM, compared to the case of uniform parallel flow. (paper)

No abstract available

[en] A review of the engineering problems related to the structures in front of the plasma of experimental Tokamak-type reactors is made. Attention is focused on the so-named ''first wall'', i.e. the wall side of the blanket segments facing the plasma, and on the collector plates of the impurity control system, in particular for the case of the single-null poloidal divertor. Even if the uncertainties related to the plasma-wall interaction are stil relevant, some engineering solutions which look manageable are identified and described. (orig.)

[en] A global model is described which calculates the impurity levels resulting from plasma and impurity sputtering. The edge temperature is determined in a self consistent way from the input power and the particle containment time. Calculations are presented for the specific case of INTOR considering both carbon and iron walls. The impurity level is very dependent on the global particle containment time. For iron walls the impurity level is probably tolerable but a large fraction of the α heating power is radiated. For carbon walls the radiation level is much lower. (orig.)

[en] Serious problems have to be faced at present in linking present plasma research to fusion reactor engineering. Even in fusion devices of the near-term and of the next generation which aim to evaluate the fusion engineering feasibility of burning plasma experiments such as TFTR, JET, R-tokamak, ZEPHYR and INTOR, plasma-material interactions cause many technological difficulties such as large heat loads, large erosion rates, large magnetic forces and large induced radioactivities. Moreover, impurity control, tritium handling, ash exhaust and refuelling need to be solved by realistic methods with technological justifications. Since present fusion approaches might not give hopeful predictions to an economical, safe, and reliable fusion reactor, it is most important at present to find a possible window of promising fusion research. In this paper, we review technological restrictions from viewpoints of plasma-material interactions, then discuss the fusion research and related material investigations that are necessary to realize reasonable fusion reactor concepts. (orig.)

No abstract available

[en] The sputtering characteristics of various types of carbon limiter surfaces, e.g. pyrolitic graphite (PG), pulverized carbon film and carbon film produced by methane discharges, are tested. Arcing is only observed on the pulverized carbon surface in a stable discharge or the other surfaces in an unstable discharge. Ion sputtering is shown to be the dominant process of carbon efflux from the normal surfaces. Employing PG limiters and a carbon wall coated by rf-sputtering method, very low q plasmas with a good confinement characteristic are obtained. The coated carbon surface is pure and still not contaminated after 600 or more discharges. (orig.)

No abstract available