Observation of an improved energy-confinement regime in neutral-beam<i>–</i>heated divertor discharges in the DIII-D tokamak

Burrell, K. H.; Ejima, S.; Dp, Schissel; Brooks, N. H.; Rw, Callis; Tn, Carlstrom; Ap, Colleraine; Jc, DeBoo; Fukumoto, Hiroaki; Rj, Groebner; Dn, Hill; Rao, Hong; Hosogane, N.; Gl, Jackson; Gl, Jahns; Janeschitz, G.; Ag, Kellman; J, Kim; Ll, Lao; P, Lee; Jm, Lohr; Jl, Luxon; Mahdavi, M. A.; Cp, Moeller; Ohyabu, N.; Osborne, T.; Overskei, D.; Pi, Petersen; Petrie, Tw; Phillips, J. C.; Prater, R.; Scoville, JT; Rp, Seraydarian; Shimada, M.; Bw, Sleaford; Rt, Snider; Rd, Stambaugh; Rd, Stav; He, St John; Stockdale, R. E.; Strait, E. J.; Taylor, T.S.; Jf, Tooker; Yamaguchi, S.

doi:10.1103/physrevlett.59.1432

Cited by 101 publications

(57 citation statements)

References 13 publications

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“…The direction of the poloidally averaged collisional ion heat flux is inward if the ion grad-B drift is towards the X-point and outward if the drift is away from the X-point. This is in qualitative agreement with experiments [3][4][5] in which the power threshold for the H-mode transition has been found to be lower if the ion grad-B drift is towards the X-point. These collisional transport effects are not responsible for the improved confinement of the H-mode, but they influence the threshold conditions.…”

Section: Introductionsupporting

confidence: 92%

Changes in Physical Property of Epoxy Resin with Absorption of Methyl Alcohol and Water

Wada

Nohara

Shintani

1994

Jpn. J. Appl. Phys.

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The collisional transport of electrons and ions in the scrape-off layer just outside the magnetic separatrix of a diverted tokamak plasma is investigated. This extends previous work by Hinton, which focused on ion transport alone and which correctly interpreted the H-mode power threshold dependence on the ion grad-B drift direction. The presence of a plasma pinch effect driven by a poloidal electron temperature gradient is predicted. This inward convection can make a significant contribution to the energy and particle confinement. The strength of this effect is computed using a simple model and DIII-D data.

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Section: Introductionsupporting

confidence: 92%

Changes in Physical Property of Epoxy Resin with Absorption of Methyl Alcohol and Water

Wada

Nohara

Shintani

1994

Jpn. J. Appl. Phys.

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“…The power threshold was found to be lower for the following cases: (9) With separatrix instead of limiter operation. (10) In deuterium instead of hydrogen plasmas; the actual value of P th depends on the isotopic mix. (11) In clean (with boronization) instead of dirty plasmas.…”

Section: The Initial Years Of H-mode Studiesmentioning

confidence: 99%

“…In this case the H-transition occurred without additional toroidal momentum input. The H-mode was reproduced in 1984 in PDX [9], in 1986 in DIII-D [10] and in 1987 in JET [11]. Finally, in 1993, the first H-mode transition was achieved in the W7-AS stellarator demonstrating that the H-mode is a generic feature of toroidal confinement [12].…”

Section: The Initial Years Of H-mode Studiesmentioning

confidence: 99%

A quarter-century of H-mode studies

Wagner

2007

Plasma Phys. Control. Fusion

362

381

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The H-mode is a confinement mode of toroidal plasmas, which may make the goals of fusion possible-the development of a clean energy source at competitive electricity costs. The most challenging aspect of the H-mode physics is the sudden disappearance of the edge turbulence whereas its driving forces-the gradients-increase. As the physics behind the H-mode is subtle many features are not yet clarified. There is, however, substantial experimental and theoretical evidence that turbulent flows, which normally limit the confinement, are diminished by sheared poloidal flow residing at the plasma edge. There are many conceivable mechanisms giving rise to sheared flow. The most intriguing of these is that fluctuations themselves induce the flow, which acts back to its generating origin and annihilates the turbulence. This review concentrates mostly on the transition physics, describes one line of understanding the H-mode in more detail, recalls some of the older observations and summarizes the achievements in the H-mode for both tokamaks and stellarators.

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“…At present, SPARC and DIII-D plasmas also differ existentially, where DIII-D has been operating since the mid-1980's [41] and SPARC operation is planned to begin in 2025 [42], however the planned REMC coils for both devices presently exist only on paper. Some important parameters for the two devices are compared in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Runaway electron deconfinement in SPARC and DIII-D by a passive 3D coil

Izzo¹,

Pusztai²,

Särkimäki³

et al. 2022

Preprint

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The operation of a 3D coil-passively driven by the current quench loop voltage-for the deconfinement of runaway electrons is modeled for disruption scenarios in the SPARC and DIII-D tokamaks. Nonlinear MHD modeling is carried out with the NIMROD code including time-dependent magnetic field boundary conditions to simulate the effect of the coil. Further modeling in some cases uses the ASCOT5 code to calculate advection and diffusion coefficients for runaway electrons based on the NIMROD-calculated fields, and the DREAM code to compute the runaway evolution in the presence of these transport coefficients. Compared with similar modeling in Tinguely, et al [2021 Nucl. Fusion 61 124003], considerably more conservative assumptions are made with the ASCOT5 results, zeroing low levels of transport, particularly in regions in which closed flux surfaces have reformed. Of three coil geometries considered in SPARC, only the n = 1 coil is found to have sufficient resonant components to suppress the runaway current growth. Without the new conservative transport assumptions, full suppression of the RE current is maintained when the TQ MHD is included in the simulation or when the RE current is limited to 250kA, but when transport in closed flux regions is fully suppressed, these scenarios allow RE beams on the order of 1-2MA to appear. Additional modeling is performed to consider the effects of the close ideal wall. In DIII-D, the current quench is modeled for both limited and diverted equilibrium shapes. In the limited shape, the onset of stochasticity is found to be insensitive to the coil current amplitude and governed largely by the evolution of the safety-factor profile. In both devices, prediction of the q-profile evolution is seen to be critical to predicting the later time effects of the coil.

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Observation of an improved energy-confinement regime in neutral-beam–heated divertor discharges in the DIII-D tokamak

Cited by 101 publications

References 13 publications

Changes in Physical Property of Epoxy Resin with Absorption of Methyl Alcohol and Water

Changes in Physical Property of Epoxy Resin with Absorption of Methyl Alcohol and Water

A quarter-century of H-mode studies

Runaway electron deconfinement in SPARC and DIII-D by a passive 3D coil

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