Formation and sustainment of a 150 kA tokamak by coaxial helicity injection

Nelson, B.A.; Jarboe, T. R.; Orvis, D. J.; McCullough, L.; Xie, Jinbo; Zhang, C; Zhou, Lepu

doi:10.1103/physrevlett.72.3666

Cited by 69 publications

(45 citation statements)

References 17 publications

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“…This method has been demonstrated in the HIT experiment at the University of Washington [41]. The basic idea is to apply a voltage across a toroidal ring gap at the vacuum vessel for injecting helicity into the plasma.…”

Section: Options For Off-axis Drivementioning

confidence: 99%

Physics basis for a spherical torus power plant

Jardin

Kessel

Ménard

et al. 2003

Fusion Engineering and Design

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The spherical torus, or low-aspect-ratio tokamak, is considered as the basis for a fusion power plant. A special class of wall-stabilized high-b high-bootstrap fraction low-aspect-ratio tokamak equilibrium are analyzed with respect to MHD stability, bootstrap current and external current drive, poloidal field system requirements, power and particle exhaust and plasma operating regime. Overall systems optimization leads to a choice of aspect ratio A0/1.6, plasma elongation k 0/3.4, and triangularity d0/0.64. The design value for the plasma toroidal b is 50%, corresponding to b N 0/7.4, (based on the toroidal b , not the total b ) which is 10% below the ideal stability limit. The bootstrap fraction of 99% greatly alleviates the current drive requirements, with tangential neutral beam injection mainly for profile control and rotation drive. The design is such that 45% of the thermal power is radiated in the plasma by Bremstrahlung and trace Krypton, with Neon in the scrapeoff layer radiating the remainder. The scarcity of spherical torus experimental data caused the design to be based largely on theoretical predictions, some of which may turn out to be overly optimistic. This highlights the need for a strong experimental research program in this area. #

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Section: Options For Off-axis Drivementioning

confidence: 99%

Physics basis for a spherical torus power plant

Jardin

Kessel

Ménard

et al. 2003

Fusion Engineering and Design

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“…If we denote by ψ(r,t) the usual cylindrical poloidal flux function, then in the presence of a strong toroidal magnetic field and of a non-inductive current drive source, we have the evolution equation: (8) with either the non-inductive boundary condition [13] (9) or the inductive boundary condition (10) In Eq. (9), we have defined the effective external inductance as Where the contribution of the vertical field (VF) is used to reduce the effective plasma inductance.…”

Section: A Simple Illustration In 1dmentioning

confidence: 99%

“…In this paper we clarify the fundamental differences between inductive and non-inductive current buildup, discuss the associated time-scales, and illuminate some of the consequences of attempting to exceed these natural time-scales. We explicitly do not consider non-axisymmetric current drive techniques such as coaxial helicity injection (CHI) [8] in the present paper.…”

Section: Introductionmentioning

confidence: 99%

Time-Scales for Non-Inductive Current Buildup in Low-Aspect-Ratio Toroidal Geometry

Jardin¹

1999

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The fundamental differences between inductive and non-inductive current buildup are clarified and the associated time-scales and other implications are discussed. A simulation is presented whereby the plasma current in a low-aspect-ratio torus is increased primarily by the self-generated bootstrap current with only 10% coming from external current drive. The maximum obtainable plasma current by this process is shown to scale with the toroidal field strength. The basic physics setting the time-scales can be obtained from a 1D analysis. Comparisons are made between the timescales found here and those reported in the experimental literature.2

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“…Profile information-reconstructed from surface probe data by an equilibrium code-indicates substantial relaxation. 6 The discharge fills the chamber and generates closed poloidal flux contours.…”

Section: Introductionmentioning

confidence: 99%

“…3 ͒ Experimentally, DC helicity injection has been explored on the Current Drive Experiment ͑CDX͒, 4,5 the Continuous Current Tokamak ͑CCT͒, 5 and the Helicity Injected Tokamak ͑HIT͒. 6 The CDX ͑and CCT͒ configuration uses a toroidally local cathode that is mounted near the surface of the chamber. The cathode emits an electron beam in one toroidal direction, and a vertical magnetic field deflects the beam toward the center of the chamber.…”

Section: Introductionmentioning

confidence: 99%

Magnetohydrodynamic simulations of direct current helicity injection for current drive in tokamaks

Sovinec

Prager

1996

Physics of Plasmas

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Magnetohydrodynamic ͑MHD͒ computations of direct current ͑DC͒ helicity injection for tokamak-like configurations show current drive with no ''loop voltage'' in a resistive, pressureless plasma. Self-consistently induced, hollow current profiles are unstable to resistive modes that partially relax the profile through the MHD dynamo mechanism. The resulting current profiles remain quite hollow, however, and tokamaks are not generated. The current driven by the fluctuations leads to closed contours of average poloidal flux, but the 1% fluctuation level is large enough to produce a region of stochastic magnetic field. A limited Lundquist number (S) scan from 2.5ϫ10 3 to 2ϫ10 4 indicates that both the fluctuation level and current profile relaxation increase with S. A simple quasilinear power scaling is consistent with these results at low S and suggests that at larger S, the fluctuation level decreases.

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Formation and sustainment of a 150 kA tokamak by coaxial helicity injection

Cited by 69 publications

References 17 publications

Physics basis for a spherical torus power plant

Physics basis for a spherical torus power plant

Time-Scales for Non-Inductive Current Buildup in Low-Aspect-Ratio Toroidal Geometry

Magnetohydrodynamic simulations of direct current helicity injection for current drive in tokamaks

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