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>H. Zohm, ''Edge localized modes (ELMs)'', [[doi:10.1088/0741-3335/38/2/001|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>
<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>[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>
* 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>[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>
* 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>[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>
* 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>[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>
* 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> [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>
* [[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>[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>
* [[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 ==
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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-mode]]s exist (without ELMs),
Although [[Quiescent H-mode]]s 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>
<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>[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>
<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 ==
== See also ==

Latest revision as of 10:52, 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:

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

References

  1. ↑ H. Zohm, Edge localized modes (ELMs), Plasma Phys. Control. Fusion 38 (1996) 105-128
  2. ↑ D.N. Hill, A review of ELMs in divertor tokamaks, Journal of Nuclear Materials 241-243 (1997) 182-198
  3. ↑ A. Takayama and M. Wakatani, ELM modelling based on the nonlinear interchange mode in edge plasma, Plasma Phys. Control. Fusion 38 (1996) 1411-1414
  4. ↑ J.W. Connor et al, Magnetohydrodynamic stability of tokamak edge plasmas, Phys. Plasmas 5 (1998) 2687
  5. ↑ P.B. Snyder et al, Edge localized modes and the pedestal: A model based on coupled peeling–ballooning modes, Phys. Plasmas 9 (2002) 2037
  6. ↑ 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
  7. ↑ N. Hayashi et al, Integrated simulation of ELM energy loss and cycle in improved H-mode plasmas, Nucl. Fusion 49 (2009) 095015
  8. ↑ C.G. Gimblett, Peeling mode relaxation ELM model, AIP Conf. Proc. 871 (2006) 87-99
  9. ↑ E.R. Solano et al, ELMs and strike point jumps, Journal of Nuclear Materials 337-339 (2005) 747-750
  10. ↑ Emilia R. Solano, Criticality of the Grad–Shafranov equation: transport barriers and fragile equilibria, Plasma Phys. Control. Fusion 46 (2004) L7-L13
  11. ↑ R. Sánchez et al, Modelling of ELM-like phenomena via mixed SOC-diffusive dynamics, Nucl. Fusion 43 (2003) 1031-1039
  12. ↑ K.H. Burrell et al, Advances in understanding quiescent H-mode plasmas in DIII-D, Phys. Plasmas 12 (2005) 056121
  13. ↑ 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
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