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The Helias Reactor Concept: Comparative Analysis of Different Field Period Configurations

Tamara Andreeva, Craig D. Beidler, Ewald Harmeyer, Yuri L. Igitkhanov, Yaroslav I. Kolesnichenko, Vadym V. Lutsenko, Alexander Shishkin, Franz Herrnegger, Johann Kißlinger, Horst F. G. Wobig

Fusion Science and Technology / Volume 46 / Number 2 / September 2004 / Pages 395-400

Technical Papers / Stellarators /

The Helias reactor (HSR) is an upgraded version of the Wendelstein 7-X (W7-X) experiment. A straightforward extrapolation of W7-X leads to a five-period configuration with a major radius of 22 m. To reduce the size of the reactor, another option with four periods has been investigated. Recent studies have focused on a three-period Helias configuration (HSR3/15i) (major radius 15 m, plasma radius 2.5 m, B = 5 T), which presents a more compact option than the five- and four-period configurations. In HSR3/15i, the resulting magnetic configuration is consistent with the island divertor concept. The stochastic region outside the last magnetic surface is imposed by the remnants of the 3/4 islands and the plasma flows along distinct channels toward the plates. The main problem is due to the high value of the bootstrap current (~1 MA) and alpha-particle losses (estimated as 6%). Further optimization of HSR3/15i can cause the maximum value of the magnetic field at the superconductive coils to be exceeded. There is a trade-off between physics goals (alpha-particle confinement and small bootstrap current) and technical realization (NbTi technology). The comparative analysis of different period configurations will be presented.

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