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Vorträge und Posterpräsentationen (mit Tagungsband-Eintrag):

G. Kamelander, G. Sdouz, G. Weimann:
"Helium Recycling Studies for Iter-Plasmas with Internal Transport Barrier";
Vortrag: Conference on Controlled Fusion and Plasma Physics, Budapest, Ungarn; 12.06.2000 - 16.06.2000; in: "Conference on Controlled Fusion and Plasma Physics 27th European Physical Society Conference on Controlled Fusion and Plasma Physics", (2000), ISBN: 9633726182; S. 229.



Kurzfassung:
The problem of generation and removal of helium ash will play a crucial role in operation of burning reactor plasmas. Recently the requirements for steady-state operation of Iter-like fusion reactors with high power amplification factor have been investigated [1] where the non-inductive, plasma current in the equilibrium is composed of fast wave current, lower hybrid current and bootstrap current. In such so-called advanced scenarios the particle and energy confinement are improved by an internal transport barrier (ITB). In Ref.[1] the helium ash has been considered prescribing the helium confinement factor - the fraction of effective helium confinement time over the energy confinement time. The numerical simulation of these advanced scenarios have been performed with the 1 1/2 dimensional fluid code ASTRA. In the actual paper the set of basic equations has been improved by a two-group model for fast alphas and helium. The Bohm/gyroBohm transport model for the bulk plasma has been extended to helium transport. Thus, the helium confinement factor is not input, as earlier, but result. Helium recycling has been modeled by means of a recycling source depending on thc effective helium confinement time. One of the main problems to be solved consisted in the application of a convenient boundary condition for the helium ash. Our investigations concentrated on two points. The first point is the quantification of the offset between confinement improvement for main plasma particles and energy and the increase of helium concentration as consequence of ITB. Furthermore we have undertaken a systematic study of the influence of boundary condition on the temporal evolution of advanced scenarios. As a third problem we continued our investigations [2] representing helium fraction and helium confinement factor as functions of the recycling factor for selected scenarios.

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