Non-Inductive Start up of QUEST Plasma by RF Power

Hanada, K.; Zushi, H.; Idei, H.; Nakamura, K.; Ishiguro, M.; Tashima, S.; Kalinnikova, E. I.; Sakamoto, M.; Hasegawa, Makoto; Fujisawa, A.; Higashijima, A.; Shoji, K.; Nakashima, Hideharu; Liu, Huixin; Mitarai, O.; Maekawa, Takashi; Fukuyama, A.; Takase, Y.; Qian, J.

doi:10.1088/1009-0630/13/3/08

Cited by 38 publications

(33 citation statements)

References 22 publications

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“…17) have resulted in a plasma start-up current of up to 66 kA with P rf 350 kW, and a plasma duration of up to 10 minutes at $20 kA was obtained. 133 On QUEST, $55 kA of start-up current was obtained and maintained for $1 s with 270 kW at 28 GHz. 134 The QUEST was able to handle the steadystate rf heat load with actively cooled tungsten limiters and PFCs.…”

Section: Solenoid-free Start-up a Motivation For St Researchmentioning

confidence: 99%

“…The longer time scale non-inductive ST operation is the goal of the QUEST device. 133 The physics steady-state conditions would be the time for the plasma to be maintained for much longer than a certain physics driven time constant such as the energy, particle, and momentum confinement time, and the current diffusion time s CD for current profile stationary conditions. Since the s CD is usually the longest physics time constant, the physics steady-state can be effectively defined as a plasma discharge time duration 2-3 s CD .…”

Section: Prospects For Steady-state High Performance Dischargesmentioning

confidence: 99%

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Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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The spherical torus or spherical tokamak (ST) is a member of the tokamak family with its aspect ratio (A = R0/a) reduced to A ∼ 1.5, well below the normal tokamak operating range of A ≥ 2.5. As the aspect ratio is reduced, the ideal tokamak beta β (radio of plasma to magnetic pressure) stability limit increases rapidly, approximately as β ∼ 1/A. The plasma current it can sustain for a given edge safety factor q-95 also increases rapidly. Because of the above, as well as the natural elongation κ, which makes its plasma shape appear spherical, the ST configuration can yield exceptionally high tokamak performance in a compact geometry. Due to its compactness and high performance, the ST configuration has various near term applications, including a compact fusion neutron source with low tritium consumption, in addition to its longer term goal of an attractive fusion energy power source. Since the start of the two mega-ampere class ST facilities in 2000, the National Spherical Torus Experiment in the United States and Mega Ampere Spherical Tokamak in UK, active ST research has been conducted worldwide. More than 16 ST research facilities operating during this period have achieved remarkable advances in all fusion science areas, involving fundamental fusion energy science as well as innovation. These results suggest exciting future prospects for ST research both near term and longer term. The present paper reviews the scientific progress made by the worldwide ST research community during this new mega-ampere-ST era.

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Section: Solenoid-free Start-up a Motivation For St Researchmentioning

confidence: 99%

Section: Prospects For Steady-state High Performance Dischargesmentioning

confidence: 99%

Recent progress on spherical torus research

Ono

Kaita

2015

Physics of Plasmas

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“…The experiments were conducted on QUEST [11][12][13][14][15], which is a medium-sized spherical tokamak (R = 0. height and diameter of the vacuum vessel (VV) is 2.8 m. Four pairs of poloidal field coils and three separated center solenoid coils are available and their combination produces various magnetic configurations [11]. Of late, the maximum pulse duration is reaching nearly 10 min.…”

Section: Experimental Apparatusmentioning

confidence: 99%

Particle balance in long duration RF driven plasmas on QUEST

Hanada

Zushi

Yoshida

et al. 2015

Journal of Nuclear Materials

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“…Such plasmas are similar in nature to those also observed in LATE [5], QUEST [6], and MAST [7]. Calculation of such equilibrium will help understand the electron and ion fluid force balance properties in these plasmas, and provide an equilibrium basis for further studies of particle orbits, plasma stability, transport, current drive, boundary, and the plasma-wall interface.…”

Section: Introductionmentioning

confidence: 64%

Two-Fluid Equilibrium Considerations of Te/Ti ≫ 1, Collisionless ST Plasmas Sustained by RF Electron Heating

Peng

Ishida²,

Takase

et al. 2014

Plasma and Fusion Research

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A solution of two-fluid (electron and ion), axisymmetric equilibrium is presented that approximates solenoidfree plasmas sustained only by RF electron heating that are recently studied in TST-2, LATE, QUEST. These plasmas indicate presence of orbit-confined energetic electrons carrying substantial toroidal current outside the last closed flux surface (LCFS); T e /T i 1 and low collisionality at modest densities within LCFS; and likely a positive plasma potential relative to the conductive vacuum vessel. A system of nonlinear second-order partial differential and algebraic equations constraining six functionals of poloidal magnetic flux or canonical angular momentum are solved. An example plasma measured in TST-2 is used to guide, by trial and error, the selection of these functionals to find appropriate solutions, while assuming peaked plasma profiles and 60% toroidal current within the LCFS. The numerical equilibrium obtained indicates a substantial ion toroidal flow and electrostatic potential so that the ion ∇p i , centrifugal, and electrostatic forces of nearly equal magnitudes combine to balance the J i × B force, differently from the massless electron fluid that satisfies ∇p e = J e × B. The calculated properties suggest additional measurements needed to refine the choices of the functional forms and improve the two-fluid equilibrium fit to such plasmas.

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Non-Inductive Start up of QUEST Plasma by RF Power

Cited by 38 publications

References 22 publications

Recent progress on spherical torus research

Recent progress on spherical torus research

Particle balance in long duration RF driven plasmas on QUEST

Two-Fluid Equilibrium Considerations of <i>T</i><sub>e</sub>/<i>T</i><sub>i </sub>≫ 1, Collisionless ST Plasmas Sustained by RF Electron Heating

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