Physics of the compact advanced stellarator NCSX

Zarnstorff, M. C.; Berry, L. A.; Brooks, A.; Fredrickson, E. D.; Fu, G. Y.; Hirshman, S. P.; Hudson, S. R.; Ku, L. P.; Lazarus, E. A.; Mikkelsen, D. R.; Monticello, D.; Neilson, G.H.; Pomphrey, N.; Reiman, A.; Spong, D. A.; Strickler, D. J.; Boozer, Allen H.; Cooper, W. A.; Goldston, Robert James; Hatcher, R.; Isaev, M. Yu.; Kessel, C.; Lewandowski, J. L. V.; Lyon, J. F.; Merkel, P.; Mynick, H.; Nelson, B.; Nuehrenberg, C.; Redi, M. H.; Reiersen, W.; Rutherford, P. H.; Sánchez, Raúl; Schmidt, J.; White, R. B.

doi:10.1088/0741-3335/43/12a/318

Cited by 173 publications

(155 citation statements)

References 43 publications

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“…In connection with it, the equilibrium reconstruction in the presence of finite pressure gradients in an ergodic edge region requires additional efforts. Nevertheless, the PIES calculations for W7-X [63] and NCSX [11] give much better results in the high-β regime. This is achieved in W7-X by the significant reduction of the Pfirsch-Schlüter current and the optimized coil field spectrum.…”

Section: Ms-313705 Final Papermentioning

confidence: 96%

“…"Reverse engineering" has constituted an innovative approach to meet desired physics targets, as realized in the WENDELSTEIN W7-X (Helias concept) [9] and the compact quasi-symmetric stellarator (QS) design (e.g. NCSX, HSX) [10,11,12]. On the other hand, configuration optimization within the device flexibility has led to considerably improved plasma confinement in the Large Helical Device (LHD, Heliotron device) without compromising stability significantly [3,13].…”

Section: Introductionmentioning

confidence: 99%

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Significance of MHD Effects in Stellarator Confinement

Weller

Sakakibara

Watanabe

et al. 2006

Fusion Science and Technology

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Substantial progress has been achieved to raise the plasma beta in stellarators and helical systems by high power neutral beam heating, approaching reactor relevant values [1][2][3]. The achievement of high-β operation is closely linked with configuration effects on the confinement and with magnetohydrodynamic (MHD) stability. However, the observed pressure gradients indicate some mitigation of the effects on the plasma confinement, presumably because of the high collisionality of high-β plasmas and island healing effects ). As far as operational limits by pressure driven MHD instabilities are concerned, only weak confinement degradation effects are usually observed, even in linearly unstable regimes.The impact of the results concerning high-β operation in W7-AS and LHD on the future stellarator programme will be discussed, including relations to tokamak research. Some of the future key issues appear to be: -the control of the magnetic configuration (including toroidal current control), -the modification of confinement and MHD properties towards the low collisional regime, -and the compatibility of high-β regimes with power and particle exhaust requirements to achieve steady state operation.

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Section: Ms-313705 Final Papermentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Significance of MHD Effects in Stellarator Confinement

Weller

Sakakibara

Watanabe

et al. 2006

Fusion Science and Technology

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show abstract

“…Even if a significant bootstrap current is generated, the negative magnetic shear prevents the destabilization of neoclassical tearing modes [2]. As a result, elaborate stability control is not required.…”

Section: Introductionmentioning

confidence: 99%

Wendelstein 7-X Program—Demonstration of a Stellarator Option for Fusion Energy

Wolf

Beidler

Dinklage

et al. 2016

IEEE Trans. Plasma Sci.

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The superconducting stellarator Wendelstein 7-X is currently being commissioned. First plasmas are expected for the second half of 2015. W7-X is designed to overcome the main drawbacks of the stellarator concept and simultaneously demonstrate its intrinsic advantages relative to the tokamaki.e., steady-state operation without the requirement of current drive or stability control. An elaborate optimization procedure was used to avoid excessive neoclassical transport losses at high plasma temperature, while simultaneously achieving satisfactory equilibrium and stability properties at high β in combination with a viable divertor concept. In addition, fastion confinement must be consistent with the requirements of alpha-heating in a power plant. Plasma operation of Wendelstein 7-X follows a staged approach following the successive completion of the in-vessel components. The main objective of Wendelstein 7-X is the demonstration of steady-state plasma at fusion relevant plasma parameters. Wendelstein 7-X will address major questions for the extrapolation of the concept to a power plant. These include divertor operation at high densities, plasma fueling at high central temperatures, avoiding impurity accumulation, and an assessment of the effect of neoclassical optimization on turbulent transport and fast-ion confinement. A power plant concept based on an extrapolation from Wendelstein 7-X, the helical advanced stellarator, has been developed.Index Terms-Fusion power plant, steady-state magnetic confinement, stellarator.

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“…1,2 The NCSX magnet system has 18 modular coils, three in each of the six stellarator-symmetric half-periods of the device, plus toroidal field coils, poloidal field coils, and helical-field trim coils. The NCSX will be used to acquire physics data needed to evaluate the compact stellarator as a fusion concept and to advance the understanding of three-dimensional ͑3-D͒ plasmas for fusion and basic science.…”

Section: Introduction and Overviewmentioning

confidence: 99%

Novel design methods for magnetic flux loops in the National Compact Stellarator Experiment

et al. 2007

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Articles you may be interested inA novel electron density reconstruction method for asymmetrical toroidal plasmas Rev. Sci. Instrum. 85, 053506 (2014);Magnetic pickup loops on the vacuum vessel ͑VV͒ can provide an abundance of equilibrium information for stellarators. A substantial effort has gone into designing flux loops for the National Compact Stellarator Experiment ͑NCSX͒ ͓Zarnstorff et al., Plasma Phys. Controlled Fusion 43, A237 ͑2001͔͒, a three-field period quasi-axisymmetric stellarator under construction at the Princeton Plasma Physics Laboratory. The design philosophy, to measure all of the magnetic field distributions normal to the VV that can be measured, has necessitated the development of singular value decomposition algorithms for identifying efficient loop locations. Fields are expected to be predominantly stellarator symmetric ͑SS͒-the symmetry of the machine design-with toroidal mode numbers per torus ͑n͒ equal to a multiple of 3 and possessing reflection symmetry in a period. However, plasma instabilities and coil imperfections will generate non-SS fields that must also be diagnosed. The measured symmetric fields will yield important information on the plasma current and pressure profile as well as on the plasma shape. All fields that obey the design symmetries could be measured by placing flux loops in a single half-period of the VV, but accurate resolution of nonsymmetric modes, quantified by the condition number of a matrix, requires repositioning loops to equivalent locations on the full torus. A subarray of loops located along the inside wall of the vertically elongated cross section was designed to detect n =3, m = 5 or 6 resonant field perturbations that can cause important islands. Additional subarrays included are continuous in the toroidal and poloidal directions. Loops are also placed at symmetry points of the VV to obtain maximal sensitivity to asymmetric perturbations. Combining results from various calculations which have made extensive use of a database of 2500 free-boundary VMEC equilibria, has led to the choice of 225 flux loops for NCSX, of which 151 have distinct shapes.

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Physics of the compact advanced stellarator NCSX

Cited by 173 publications

References 43 publications

Significance of MHD Effects in Stellarator Confinement

Significance of MHD Effects in Stellarator Confinement

Wendelstein 7-X Program—Demonstration of a Stellarator Option for Fusion Energy

Novel design methods for magnetic flux loops in the National Compact Stellarator Experiment

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