H-mode: Difference between revisions
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When a magnetically confined plasma is heated strongly, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state. | When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state. | ||
<ref>[http://link.aps.org/doi/10.1103/PhysRevLett.53.1453 F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]</ref> | <ref>[http://link.aps.org/doi/10.1103/PhysRevLett.53.1453 F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]</ref> | ||
In the H-mode, the [[Energy confinement time|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more. | In the H-mode, the [[Energy confinement time|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more. | ||
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<ref>[http://dx.doi.org/10.1088/0741-3335/49/12B/S01 F. Wagner, ''A quarter-century of H-mode studies'', Plasma Phys. Control. Fusion '''49''' (2007) B1-B33]</ref> | <ref>[http://dx.doi.org/10.1088/0741-3335/49/12B/S01 F. Wagner, ''A quarter-century of H-mode studies'', Plasma Phys. Control. Fusion '''49''' (2007) B1-B33]</ref> | ||
The precise mechanism governing this phenomenon is the subject of ongoing studies. | The precise mechanism governing this phenomenon is the subject of ongoing studies. | ||
== ELMs == | == ELMs == | ||
Revision as of 11:07, 25 August 2009
When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state. [1] In the H-mode, the energy confinement time is significantly enhanced, i.e., typically by a factor of 2 or more. [2]
Physical mechanism
This transport bifurcation is the consequence of the suppression of turbulence in the edge plasma, induced by a sheared flow layer and an associated edge radial electric field. [3] The precise mechanism governing this phenomenon is the subject of ongoing studies.
ELMs
The steep edge gradients (of density and temperature) lead to quasi-periodic violent relaxation phenomena, known as Edge Localized Modes (ELMs), which have a strong impact on the surrounding vessel. [4] The ELMy H-mode is proposed as the standard operating scenario for ITER, thus converting ELM mitigation into a priority. [5]
References
- ↑ F. Wagner et al, Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX, Phys. Rev. Lett. 53 (1984) 1453 - 1456
- ↑ M. Keilhacker, H-mode confinement in tokamaks, Plasma Phys. Control. Fusion 29 (1987) 1401-1413
- ↑ F. Wagner, A quarter-century of H-mode studies, Plasma Phys. Control. Fusion 49 (2007) B1-B33
- ↑ D.N. Hill, A review of ELMs in divertor tokamaks, Journal of Nuclear Materials 241-243 (1997) 182-198
- ↑ M.R. Wade, Physics and engineering issues associated with edge localized mode control in ITER, Fusion Engineering and Design 84, Issues 2-6 (2009) 178-185