Development of an ITER relevant advanced scenario at ASDEX Upgrade
- Max-Planck-Institut fuer Plasmaphysik, European Atomic Energy Community (EURATOM) Association, 85748 Garching (Germany)
The 'improved H-mode', realized in ASDEX Upgrade [A. Herrmann and O. Gruber, Fusion Sci. Technol. 44, 569 (2003)] in 1998, demonstrates that advanced requirements beyond the standard H-mode for confinement [confinement enhancement factor H{sub 98(y,2)}>1], stability (normalized beta {beta}{sub N}{approx}3-3.5) and, at densities close to Greenwald density, exhaust can be simultaneously met and maintained stationary for several resistive diffusion times. The q profile is characterized by low central magnetic shear and axis safety factor q{sub 0}>1 that is obtained by particular heating and current ramp-up scenarios and maintained via benign instabilities. Core transport is still governed by drift-wave turbulence with stiff temperature profiles, but density profiles are more strongly peaked and contribute to the increase in confinement. Neoclassical tearing modes remain small, enabling routine operation up to {beta}{sub N}{approx}3 at international thermonuclear experimental reactor (ITER) relevant collisionalities, for normalized Lamor radii down to four times the ITER value and for a broad range of q{sub 95}=3.2-4.5. Using tailored heat deposition including central wave heating a compromise was found in density peaking for enhanced confinement and limiting the high-Z impurity concentrations even with a tungsten-coated first wall and divertor. As far as the ITER [ITER EDA Documentation Series No. 24, 2002] relevance of this regime is concerned, its compatibility with significant central electron heating, high edge densities, and type-II edge localized modes is of importance. The GLF23 turbulence model predicts still peaked density profiles and sufficient transport to avoid impurity accumulation. The fusion performance in terms of {beta}{sub N}H{sub 98(y,2)}/q{sub 95}{sup 2} is nearly doubled compared with the ITER base-line scenario at low-q values, while at medium q's bootstrap current fractions up to 50% and long inductive pulse lengths allow ITER 'hybrid' operation.
- OSTI ID:
- 20736592
- Journal Information:
- Physics of Plasmas, Vol. 12, Issue 5; Other Information: DOI: 10.1063/1.1913641; (c) 2005 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 1070-664X
- Country of Publication:
- United States
- Language:
- English
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