Volt-second analysis and consumption in Doublet III plasmas

Ejima, S.; Callis, R.W.; Luxon, J.L.; Stambaugh, R.D.; Taylor, T.S.; Wesley, J.C.

doi:10.1088/0029-5515/22/10/006

Cited by 85 publications

(78 citation statements)

References 9 publications

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“…The most commonly used method of flux consumption analysis was first applied to the Doublet III device by Ejima [17]. This method is derived from a global electromagnetic power balance using the poloidal field (PF) portion of Poynting's theorem.…”

Section: The Poynting Methodsmentioning

confidence: 99%

Ohmic Flux Consumption During Initial Operation of the NSTX Spherical Torus

Ménard¹,

LeBlanc²,

Sabbagh³

et al. 2000

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Abstract. The spherical tokamak (ST), because of its slender central column, has very limited voltsecond capability relative to a standard aspect ratio tokamak of similar plasma cross-section. Recent experiments on the National Spherical Torus Experiment (NSTX) have begun to quantify and optimize the ohmic current drive efficiency in a MA-class ST device. Sustainable ramp-rates in excess of 5MA/sec during the current rise phase have been achieved on NSTX, while faster ramps generate significant MHD activity. Discharges with I P exceeding 1MA have been achieved in NSTX with nominal parameters: aspect ratio A=1.3-1.4, elongation κ=2-2.2, triangularity δ=0.4, internal inductance l i =0.6, and Ejima coefficient C E =0.35. Flux consumption efficiency results, performance improvements associated with first boronization, and comparisons to neoclassical resistivity are described.

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Section: The Poynting Methodsmentioning

confidence: 99%

Ohmic Flux Consumption During Initial Operation of the NSTX Spherical Torus

Ménard¹,

LeBlanc²,

Sabbagh³

et al. 2000

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“…11(a). The uniform E-field, estimated as the time derivative of the resistive flux [21], is E = 0.038 ± 0.003 V/m and the core temperature is 3.8 keV. The determination Figure 11.…”

Section: The Relative Importance Of the Avalanche Effectmentioning

confidence: 99%

Kinetic modelling of runaway electron avalanches in tokamak plasmas

Nilsson

Decker

Peysson

et al. 2015

Plasma Phys. Control. Fusion

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Runaway electrons can be generated in tokamak plasmas if the accelerating force from the toroidal electric field exceeds the collisional drag force owing to Coulomb collisions with the background plasma. In ITER, disruptions are expected to generate runaway electrons mainly through knock-on collisions [1], where enough momentum can be transferred from existing runaways to slow electrons to transport the latter beyond a critical momentum, setting off an avalanche of runaway electrons. Since knock-on runaways are usually scattered off with a significant perpendicular component of the momentum with respect to the local magnetic field direction, these particles are highly magnetized. Consequently, the momentum dynamics require a full 3-D kinetic description, since these electrons are highly sensitive to the magnetic non-uniformity of a toroidal configuration. For this purpose, a bounce-averaged knockon source term is derived. The generation of runaway electrons from the combined effect of Dreicer mechanism and knock-on collision process is studied with the code LUKE, a solver of the 3-D linearized bounce-averaged relativistic electron Fokker-Planck equation [2], through the calculation of the response of the electron distribution function to a constant parallel electric field. The model, which has been successfully benchmarked against the standard Dreicer runaway theory now describes the runaway generation by knock-on collisions as proposed by Rosenbluth [3]. This paper shows that the avalanche effect can be important even in non-disruptive scenarios. Runaway formation through knock-on collisions is found to be strongly reduced when taking place off the magnetic axis, since trapped electrons can not contribute to the runaway electron population. Finally, the relative importance of the avalanche mechanism is investigated as a function of the key parameters for runaway electron formation, namely the plasma temperature and the electric field strength. In agreement with theoretical predictions, the LUKE simulations show that in low temperature and electric field the knock-on collisions becomes the dominant source of runaway electrons and can play a significant role for runaway electron generation, including in non-disruptive tokamak scenarios.

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“…In addition to the prediction of the vacuum field evolution, initial guess of I p evolution is required for the estimation of the required vertical field for the equilibrium. By introducing C Ejima , Ejima coefficient, for resistive consumption during ramp-up phase, I p evolution can be expressed as following [13,14,17]:…”

Section: Development Of the Start-up Design Codementioning

confidence: 99%

Plasma start-up design and first plasma experiment in VEST

Lee

et al. 2015

Fusion Engineering and Design

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Volt-second analysis and consumption in Doublet III plasmas

Cited by 85 publications

References 9 publications

Ohmic Flux Consumption During Initial Operation of the NSTX Spherical Torus

Ohmic Flux Consumption During Initial Operation of the NSTX Spherical Torus

Kinetic modelling of runaway electron avalanches in tokamak plasmas

Plasma start-up design and first plasma experiment in VEST

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