H-mode: Difference between revisions
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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. | ||
<ref>[http://dx.doi.org/10.1088/0741-3335/29/10A/320 M. Keilhacker, ''H-mode confinement in tokamaks'', Plasma Phys. Control. Fusion '''29''' (1987) 1401-1413]</ref> | <ref>[http://dx.doi.org/10.1088/0741-3335/29/10A/320 M. Keilhacker, ''H-mode confinement in tokamaks'', Plasma Phys. Control. Fusion '''29''' (1987) 1401-1413]</ref> | ||
== 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. | 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. | ||
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The transition occurs spontaneously when a certain threshold value of the heating power is exceeded. | The transition occurs spontaneously when a certain threshold value of the heating power is exceeded. | ||
== 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. | 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. | ||
<ref>[http://dx.doi.org/10.1016/S0022-3115(97)80039-6 D.N. Hill, ''A review of ELMs in divertor tokamaks'', Journal of Nuclear Materials '''241-243''' (1997) 182-198]</ref> | <ref>[http://dx.doi.org/10.1016/S0022-3115(97)80039-6 D.N. Hill, ''A review of ELMs in divertor tokamaks'', Journal of Nuclear Materials '''241-243''' (1997) 182-198]</ref> | ||
The ELMy H-mode is proposed as the standard operating scenario for [[ITER]], thus converting ELM mitigation into a priority. | The ELMy H-mode is proposed as the standard operating scenario for [[ITER]], thus converting ELM mitigation into a priority. | ||
<ref>[http://dx.doi.org/10.1088/1742-6596/123/1/012002 N. Oyama, ''Progress and issues in understanding the physics of ELM dynamics, ELM mitigation, and ELM control'', J. Phys.: Conf. Ser. '''123''' (2008) 012002]</ref> | |||
== References == | == References == | ||
<references /> | <references /> | ||
Revision as of 07:26, 25 August 2009
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. [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.
The transition occurs spontaneously when a certain threshold value of the heating power is exceeded.
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
- ↑ N. Oyama, Progress and issues in understanding the physics of ELM dynamics, ELM mitigation, and ELM control, J. Phys.: Conf. Ser. 123 (2008) 012002