Edge Localized Modes: Difference between revisions
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The steep edge gradients (of density and temperature) associated with an [[H-mode]] 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) associated with an [[H-mode]] lead to quasi-periodic violent relaxation phenomena, known as Edge Localized Modes (ELMs), which have a strong impact on the surrounding vessel. | ||
<ref>[ | <ref>H. Zohm, ''Edge localized modes (ELMs)'', [[doi:10.1088/0741-3335/38/2/001|Plasma Phys. Control. Fusion '''38''' (1996) 105-128]]</ref> | ||
<ref> | <ref>D.N. Hill, ''A review of ELMs in divertor tokamaks'', [[doi:10.1016/S0022-3115(97)80039-6|Journal of Nuclear Materials '''241-243''' (1997) 182-198]]</ref> | ||
== Physical mechanism == | == Physical mechanism == | ||
The physical mechanism of ELMs has not been fully clarified. Several possible explanations have been put forward: | The physical mechanism of ELMs has not been fully clarified. Several possible explanations have been put forward: | ||
* Nonlinear interchange modes <ref> | * Nonlinear interchange modes <ref>A. Takayama and M. Wakatani, ''ELM modelling based on the nonlinear interchange mode in edge plasma'', [[doi:10.1088/0741-3335/38/8/046|Plasma Phys. Control. Fusion '''38''' (1996) 1411-1414]]</ref> | ||
* Coupled peeling-ballooning modes <ref> | * Coupled [[peeling-ballooning modes]] <ref>J.W. Connor et al, ''Magnetohydrodynamic stability of tokamak edge plasmas'', [[doi:10.1063/1.872956|Phys. Plasmas '''5''' (1998) 2687]]</ref><ref>P.B. Snyder et al, ''Edge localized modes and the pedestal: A model based on coupled peeling–ballooning modes'', [[doi:10.1063/1.1449463|Phys. Plasmas '''9''' (2002) 2037]]</ref><ref>J.-S. Lönnroth et al, ''Predictive transport modelling of type I ELMy H-mode dynamics using a theory-motivated combined ballooning–peeling model'', [[doi:10.1088/0741-3335/46/8/003|Plasma Phys. Control. Fusion '''46''' (2004) 1197-1215]]</ref><ref>N. Hayashi et al, ''Integrated simulation of ELM energy loss and cycle in improved H-mode plasmas'', [[doi:10.1088/0029-5515/49/9/095015|Nucl. Fusion '''49''' (2009) 095015]]</ref> | ||
* Peeling modes <ref> | * Peeling modes <ref>C.G. Gimblett, ''Peeling mode relaxation ELM model'', [[doi:10.1063/1.2404542|AIP Conf. Proc. '''871''' (2006) 87-99]]</ref> | ||
* Flux surface peeling <ref> | * Flux surface peeling <ref>E.R. Solano et al, ''ELMs and strike point jumps'', [[doi:10.1016/j.jnucmat.2004.09.067|Journal of Nuclear Materials '''337-339''' (2005) 747-750]]</ref> | ||
* [[Criticality of MHD equilibrium]] <ref> | * [[Criticality of MHD equilibrium]] <ref>Emilia R. Solano, ''Criticality of the Grad–Shafranov equation: transport barriers and fragile equilibria'', [[doi:10.1088/0741-3335/46/3/L02|Plasma Phys. Control. Fusion '''46''' (2004) L7-L13]]</ref> | ||
* [[Self-Organised Criticality]] <ref> | * [[Self-Organised Criticality]] <ref>R. Sánchez et al, ''Modelling of ELM-like phenomena via mixed SOC-diffusive dynamics'', [[doi:10.1088/0029-5515/43/10/003|Nucl. Fusion '''43''' (2003) 1031-1039]]</ref> | ||
== ELMs and machine operation == | == ELMs and machine operation == | ||
The occurrence of an ELM leads to a significant expulsion of heat and particles, with deleterious consequences for the vessel wall and machine operation. | The occurrence of an ELM leads to a significant expulsion of heat and particles, with deleterious consequences for the vessel wall and machine operation. | ||
Although Quiescent H- | Although [[Quiescent H-mode]]s exist (without ELMs), | ||
<ref> | <ref>K.H. Burrell et al, ''Advances in understanding quiescent H-mode plasmas in DIII-D'', [[doi:10.1063/1.1894745|Phys. Plasmas '''12''' (2005) 056121]]</ref> | ||
they are generally considered not convenient due to the accumulation of impurities. | they are generally considered not convenient due to the accumulation of [[impurities]]. | ||
To achieve steady state, an ELMy H-mode is preferred and this mode of operation is proposed as the standard operating scenario for [[ITER]], thus converting ELM mitigation into a priority. | To achieve steady state, an ELMy H-mode is preferred and this mode of operation is proposed as the standard operating scenario for [[ITER]], thus converting ELM mitigation into a priority. | ||
<ref> | <ref>M.R. Wade, ''Physics and engineering issues associated with edge localized mode control in ITER'', [[doi:10.1016/j.fusengdes.2009.01.063|Fusion Engineering and Design '''84''', Issues 2-6 (2009) 178-185]]</ref> | ||
== See also == | |||
* [[Resonant Magnetic Perturbation]], an ELM mitigation technique | |||
== References == | == References == | ||
<references /> | <references /> | ||
Latest revision as of 09:52, 3 April 2018
The steep edge gradients (of density and temperature) associated with an H-mode lead to quasi-periodic violent relaxation phenomena, known as Edge Localized Modes (ELMs), which have a strong impact on the surrounding vessel. [1] [2]
Physical mechanism
The physical mechanism of ELMs has not been fully clarified. Several possible explanations have been put forward:
- Nonlinear interchange modes [3]
- Coupled peeling-ballooning modes [4][5][6][7]
- Peeling modes [8]
- Flux surface peeling [9]
- Criticality of MHD equilibrium [10]
- Self-Organised Criticality [11]
ELMs and machine operation
The occurrence of an ELM leads to a significant expulsion of heat and particles, with deleterious consequences for the vessel wall and machine operation. Although Quiescent H-modes exist (without ELMs), [12] they are generally considered not convenient due to the accumulation of impurities. To achieve steady state, an ELMy H-mode is preferred and this mode of operation is proposed as the standard operating scenario for ITER, thus converting ELM mitigation into a priority. [13]
See also
- Resonant Magnetic Perturbation, an ELM mitigation technique
References
- ↑ H. Zohm, Edge localized modes (ELMs), Plasma Phys. Control. Fusion 38 (1996) 105-128
- ↑ D.N. Hill, A review of ELMs in divertor tokamaks, Journal of Nuclear Materials 241-243 (1997) 182-198
- ↑ A. Takayama and M. Wakatani, ELM modelling based on the nonlinear interchange mode in edge plasma, Plasma Phys. Control. Fusion 38 (1996) 1411-1414
- ↑ J.W. Connor et al, Magnetohydrodynamic stability of tokamak edge plasmas, Phys. Plasmas 5 (1998) 2687
- ↑ P.B. Snyder et al, Edge localized modes and the pedestal: A model based on coupled peeling–ballooning modes, Phys. Plasmas 9 (2002) 2037
- ↑ J.-S. Lönnroth et al, Predictive transport modelling of type I ELMy H-mode dynamics using a theory-motivated combined ballooning–peeling model, Plasma Phys. Control. Fusion 46 (2004) 1197-1215
- ↑ N. Hayashi et al, Integrated simulation of ELM energy loss and cycle in improved H-mode plasmas, Nucl. Fusion 49 (2009) 095015
- ↑ C.G. Gimblett, Peeling mode relaxation ELM model, AIP Conf. Proc. 871 (2006) 87-99
- ↑ E.R. Solano et al, ELMs and strike point jumps, Journal of Nuclear Materials 337-339 (2005) 747-750
- ↑ Emilia R. Solano, Criticality of the Grad–Shafranov equation: transport barriers and fragile equilibria, Plasma Phys. Control. Fusion 46 (2004) L7-L13
- ↑ R. Sánchez et al, Modelling of ELM-like phenomena via mixed SOC-diffusive dynamics, Nucl. Fusion 43 (2003) 1031-1039
- ↑ K.H. Burrell et al, Advances in understanding quiescent H-mode plasmas in DIII-D, Phys. Plasmas 12 (2005) 056121
- ↑ 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