| INSTITUTE OF PHYSICS PUBLISHING PLASMA PHYSICS AND CONTROLLED FUSION Plasma Phys. Control. Fusion 45 (2003) A285–A308 PII: S0741-3335(03)67725-0 Experiments close to the beta-limit in W7-AS (2007) | |||||||||||||
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Abstract | |||||||||||||
| A major objective of the experimental program in the last phase of the W7-AS stellarator was to explore and demonstrate the high-β performance of advanced stellarators. MHD-quiescent discharges at low impurity radiation levels with volume averaged β-values of up to 〈β 〉 =3.4 % have been achieved. A very important prerequisite was the attainment of the high density H-Mode (HDH) regime. This was made possible by the installation of extensive graphite plasma facing components designed for island divertor operation. The co-directed neutral beam injection provided increased absorbed heating power of up to 3.2 MW in high-β plasmas with B � 1.25 T. The anticipated improved features concerning equilibrium and stability at high plasma β could be verified experimentally by the comparison of x-ray data with free boundary equilibrium calculations. The maximum β found in configurations with a rotational transform around ̷ι = 0.5 is determined by the available heating power. No evidence of a stability limit has been found in the accessible configuration space, | |||||||||||||
Details der Publikation | |||||||||||||
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