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Abstract

Impurities determine radiation losses, contribute to fuel dilution and hence play an important role in fusion plasmas. In view of advanced, strongly shaped reactor designs, one important and frequently neglected aspect is the effect of operating modes and plasma geometry on the confinement of fuel particles and impurities, specifically in relation with the energy confinement. The extreme shaping capabilities of TCV (Tokamak a Configuration Variable, R = 0.88 m, a = 0.25 m, vacuum vessel elongation k=3 and vacuum central magnetic field B </= 1.51 T) allow the exploration of the effects of plasma geometry on both energy and impurity transport and confinement.

Small non perturbing quantities of laser-ablated impurities were injected into Ohmic plasmas in TCV and the time evolution of the soft X-ray emission was measured. The global lifetime of the impurities was obtained from the exponential decay of the X-ray emissions after the influx phase. For constant plasma geometry a correlation between the lifetime t(imp) and the line aver- aged electron density is observed. Remarkably this lifetime decreases in higher elongation plasmas and more importantly the ratio t(imp)/t(Ee) is reduced as well by a factor 3 when the elongation is increased from k =1.6 to k =2.3.

By means of the I-D particle transport code STRAHL[I] the radial dependence of transport parameters (diffusion coefficient and convective velocity) has been modelled for different plasma configurations. ns.

Additional information

Authors: SCAVINO E, Centre de Recherches en Physique des Plasmas, EURATOM Association-Confederation Suisse, Ecole Polytechnique Federale de Lausanne (CH);WEISEN H, Centre de Recherches en Physique des Plasmas, EURATOM Association-Confederation Suisse, Ecole Polytechnique Federale de Lausanne (CH);ZABOLOTSKY A, Centre de Recherches en Physique des Plasmas, EURATOM Association-Confederation Suisse, Ecole Polytechnique Federale de Lausanne (CH);BAKOS J.S, KFKI Research Institute for Particle and Nuclear Physics, Budapest (HU)
Bibliographic Reference: An oral report given at: The 28th EPS Conference of Controlled Fusion and Plasma Physics. Held in: Madeira (PT) June 2001
Record Number: 200013703 / Last updated on: 2001-09-18
Category: PUBLICATION
Original language: en
Available languages: en