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>[http://dx.doi.org/10.1088/0741-3335/38/2/001 H. Zohm, ''Edge localized modes (ELMs)'', Plasma Phys. Control. Fusion '''38''' (1996) 105-128]</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> | |||
== 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 | * Nonlinear interchange modes <ref>[http://dx.doi.org/10.1088/0741-3335/38/8/046 A. Takayama and M. Wakatani, ''ELM modelling based on the nonlinear interchange mode in edge plasma'', Plasma Phys. Control. Fusion '''38''' (1996) 1411-1414]</ref> | ||
* Coupled peeling-ballooning modes | * Coupled peeling-ballooning modes <ref>[http://link.aip.org/link/?PHPAEN/5/2687/1 J.W. Connor et al, ''Magnetohydrodynamic stability of tokamak edge plasmas'', Phys. Plasmas '''5''' (1998) 2687]</ref><ref>[http://link.aip.org/link/?PHPAEN/9/2037/1 P.B. Snyder et al, ''Edge localized modes and the pedestal: A model based on coupled peeling–ballooning modes'', Phys. Plasmas '''9''' (2002) 2037]</ref><ref>[http://dx.doi.org/10.1088/0741-3335/46/8/003 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]</ref><ref>[http://dx.doi.org/10.1088/0029-5515/49/9/095015 N. Hayashi et al, ''Integrated simulation of ELM energy loss and cycle in improved H-mode plasmas'', Nucl. Fusion '''49''' (2009) 095015]</ref> | ||
* Peeling modes | * Peeling modes <ref>[http://link.aip.org/link/?APCPCS/871/87/1 C.G. Gimblett, ''Peeling mode relaxation ELM model'', AIP Conf. Proc. '''871''' (2006) 87-99]</ref> | ||
* Flux surface peeling | * Flux surface peeling <ref>[http://dx.doi.org/10.1016/j.jnucmat.2004.09.067 E.R. Solano et al, ''ELMs and strike point jumps'', Journal of Nuclear Materials '''337-339''' (2005) 747-750 ]</ref> | ||
* [[Criticality of MHD equilibrium]] | * [[Criticality of MHD equilibrium]] <ref> [http://dx.doi.org/10.1088/0741-3335/46/3/L02 Emilia R. Solano, ''Criticality of the Grad–Shafranov equation: transport barriers and fragile equilibria'', Plasma Phys. Control. Fusion '''46''' (2004) L7-L13] </ref> | ||
* [[Self-Organised Criticality]] | * [[Self-Organised Criticality]] <ref>[http://dx.doi.org/10.1088/0029-5515/43/10/003 R. Sánchez et al, ''Modelling of ELM-like phenomena via mixed SOC-diffusive dynamics'', Nucl. Fusion '''43''' (2003) 1031-1039 ]</ref> | ||
== ELMs and machine operation == | == ELMs and machine operation == | ||
| Line 17: | Line 18: | ||
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-modes exist (without ELMs), | Although Quiescent H-modes exist (without ELMs), | ||
<ref>[http://link.aip.org/link/?PHPAEN/12/056121/1 K.H. Burrell et al, ''Advances in understanding quiescent H-mode plasmas in DIII-D'', 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>[http://dx.doi.org/10.1016/j.fusengdes.2009.01.063 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]</ref> | |||
== References == | == References == | ||
<references /> | |||
Revision as of 02:17, 24 November 2010
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>H. Zohm, Edge localized modes (ELMs), Plasma Phys. Control. Fusion 38 (1996) 105-128</ref> <ref>D.N. Hill, A review of ELMs in divertor tokamaks, Journal of Nuclear Materials 241-243 (1997) 182-198</ref>
Physical mechanism
The physical mechanism of ELMs has not been fully clarified. Several possible explanations have been put forward:
- Nonlinear interchange modes <ref>A. Takayama and M. Wakatani, ELM modelling based on the nonlinear interchange mode in edge plasma, Plasma Phys. Control. Fusion 38 (1996) 1411-1414</ref>
- Coupled peeling-ballooning modes <ref>J.W. Connor et al, Magnetohydrodynamic stability of tokamak edge plasmas, 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, 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, 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, Nucl. Fusion 49 (2009) 095015</ref>
- Peeling modes <ref>C.G. Gimblett, Peeling mode relaxation ELM model, AIP Conf. Proc. 871 (2006) 87-99</ref>
- Flux surface peeling <ref>E.R. Solano et al, ELMs and strike point jumps, Journal of Nuclear Materials 337-339 (2005) 747-750 </ref>
- Criticality of MHD equilibrium <ref> Emilia R. Solano, Criticality of the Grad–Shafranov equation: transport barriers and fragile equilibria, Plasma Phys. Control. Fusion 46 (2004) L7-L13 </ref>
- Self-Organised Criticality <ref>R. Sánchez et al, Modelling of ELM-like phenomena via mixed SOC-diffusive dynamics, Nucl. Fusion 43 (2003) 1031-1039 </ref>
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), <ref>K.H. Burrell et al, Advances in understanding quiescent H-mode plasmas in DIII-D, Phys. Plasmas 12 (2005) 056121</ref> 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. <ref>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</ref>
References
<references />