1993
DOI: 10.1103/physrevlett.70.2086
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Hmode of the W 7-AS stellarator

Abstract: In W 7-AS the H mode has been observed for the first time in a currentless stellarator plasma. H modes are achieved with 0.4 MW electron cyclotron resonance heating at 140 GHz at high density. The H phases display all characteristics known from tokamak H modes including edge localized modes (ELMs). The achievement of the H mode in a shear-free stellarator without toroidal current has consequences on //-mode transition and ELM theories.

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Cited by 151 publications
(47 citation statements)
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“…18,19 Before these findings, bifurcation of the radial electric field had been expected in toroidal helical plasmas by a neoclassical theory including helical ripple diffusion. [20][21][22] In contrast to tokamaks, the neoclassical theory had predicted that the absolute value of the radial electric field affected the transport in toroidal helical plasmas.…”
Section: Introductionmentioning
confidence: 99%
“…18,19 Before these findings, bifurcation of the radial electric field had been expected in toroidal helical plasmas by a neoclassical theory including helical ripple diffusion. [20][21][22] In contrast to tokamaks, the neoclassical theory had predicted that the absolute value of the radial electric field affected the transport in toroidal helical plasmas.…”
Section: Introductionmentioning
confidence: 99%
“…Clear evidence of further confinement improvement has also been observed. [4][5][6] However, the enhancement factor of confinement has been smaller than in large tokamaks. The reasons can be attributed to connection of the boundary where neutrals and atomic processes play an essential role and the core where high-temperature plasmas are contained.…”
Section: 2mentioning
confidence: 99%
“…The enhanced confinement is attributed to an edge temperature pedestal [12,13,14], which is not generally observed in other stellarators but is not attributed to an H-mode in LHD. The pedestal may be associated with a chain of magnetic islands at or near the plasma edge [12], while avoidance of island chains at low order rational i values is associated with H-modes in W7-AS [15,16].…”
Section: -5mentioning
confidence: 99%
“…In stellarator H-modes the energy confinement is enhanced modestly (no more than 30%) in W7-AS [15,16] and CHS [53,54,55,56]. Access is typically restricted to narrow ranges ini that minimize damping of poloidal rotation at the plasma boundary by avoiding island chains [57,58] (in W7-AS toroidal rotation is strongly damped by toroidal mirrors, but poloidal rotation is possible).…”
Section: Enhanced Confinement Regimes In Stellaratorsmentioning
confidence: 99%