Magnetic island - Revision history

Rkba39f8: /* See also */

2023-04-06T07:19:53Z

Admin at 10:45, 26 January 2023

2023-01-26T10:45:56Z

← Older revision		Revision as of 12:45, 26 January 2023
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	The interaction of neighbouring island chains causes the magnetic field to become stochastic (according to the Chirikov criterion <ref>B.V. Chirikov, ''A universal instability of many-dimensional oscillator systems'', [[doi:10.1016/0370-1573(79)90023-1\|Phys. Rep. '''52''', Issue 5 (1979) 263]]</ref>), resulting in enhanced (anomalous) radial transport.		The interaction of neighbouring island chains causes the magnetic field to become stochastic (according to the Chirikov criterion <ref>B.V. Chirikov, ''A universal instability of many-dimensional oscillator systems'', [[doi:10.1016/0370-1573(79)90023-1\|Phys. Rep. '''52''', Issue 5 (1979) 263]]</ref>), resulting in enhanced (anomalous) radial transport.
	<ref>C.W. Horton, Y.H. Ichikawa, ''Chaos and structures in nonlinear plasmas'', World Scientific, 1996 ISBN 9789810226367</ref>		<ref>C.W. Horton, Y.H. Ichikawa, ''Chaos and structures in nonlinear plasmas'', World Scientific, 1996 {{ISBN\|9789810226367}}</ref>

	== Island control ==		== Island control ==

Admin: /* Island birth */

2018-09-28T14:06:43Z

Island birth

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	== Island birth ==		== Island birth ==

	The rupture of the assumed initial topology of toroidally nested flux surfaces needed to produce the island requires the reconnection of magnetic field lines, which can only occur with finite resistivity.		The rupture of the assumed initial topology of toroidally nested flux surfaces needed to produce the island requires the [[reconnection]] of magnetic field lines, which can only occur with finite resistivity.
	<ref>F.L. Waelbroeck, ''Theory and observations of magnetic islands'', [[doi:10.1088/0029-5515/49/10/104025\|Nucl. Fusion '''49''' (2009) 104025]]</ref>		<ref>F.L. Waelbroeck, ''Theory and observations of magnetic islands'', [[doi:10.1088/0029-5515/49/10/104025\|Nucl. Fusion '''49''' (2009) 104025]]</ref>
	[[Stellarator]]s may have a vacuum magnetic field structure that already contains some islands (so-called 'natural islands').		[[Stellarator]]s may have a vacuum magnetic field structure that already contains some islands (so-called 'natural islands').

Admin at 09:37, 14 December 2014

2014-12-14T09:37:02Z

Admin at 09:33, 7 August 2011

2011-08-07T09:33:35Z

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	A magnetic island is a closed magnetic flux tube (cf. [[Flux surface]]), bounded by a [[Separatrix\|separatrix]], isolating it from the rest of space.		A magnetic island is a closed magnetic [[Flux tube\|flux tube]] (cf. [[Flux surface]]), bounded by a [[Separatrix\|separatrix]], isolating it from the rest of space.
	Its topology is toroidal.		Its topology is toroidal.

87.220.93.192: /* Island control */

2011-07-09T09:06:15Z

Island control

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	Pressure effects can lead to 'island healing'.		Pressure effects can lead to 'island healing'.
	<ref>[http://dx.doi.org/10.1088/0029-5515/45/7/006 R. Kanno et al, ''Formation and healing of n = 1 magnetic islands in LHD equilibrium'', Nucl. Fusion '''45''' (2005) 588]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/45/7/006 R. Kanno et al, ''Formation and healing of n = 1 magnetic islands in LHD equilibrium'', Nucl. Fusion '''45''' (2005) 588]</ref>
	Active control of islands by external means - in particular, Electron Cyclotron Heating and Current Drive - is also possible ~~(cf~~. ~~the 'Seek and destroy' technique, under development~~ <ref>[http://www.rijnhuizen.nl/en/node/195 Seek and Destroy System for magnetic island control]</ref>		Active control of islands by external means - in particular, Electron Cyclotron Heating and Current Drive - is also possible.
	<ref>[http://dx.doi.org/10.1088/0029-5515/51/4/043007 B. Ayten et al., ''Modelling of tearing mode suppression experiments in TEXTOR based on the generalized Rutherford equation'', Nucl. Fusion '''51''' (2011) 043007]</ref>).		<ref>[http://www.rijnhuizen.nl/en/node/195 Seek and Destroy System for magnetic island control]</ref>
			<ref>[http://dx.doi.org/10.1088/0029-5515/49/5/055006 A. Isayama et al, ''Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U'', Nucl. Fusion '''49''' (2009) 055006]</ref>
			<ref>[http://dx.doi.org/10.1088/0029-5515/51/4/043007 B. Ayten et al., ''Modelling of tearing mode suppression experiments in TEXTOR based on the generalized Rutherford equation'', Nucl. Fusion '''51''' (2011) 043007]</ref>

	== See also ==		== See also ==

Admin: /* Island control */

2011-04-19T06:27:37Z

Island control

← Older revision		Revision as of 08:27, 19 April 2011
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	Pressure effects can lead to 'island healing'.		Pressure effects can lead to 'island healing'.
	<ref>[http://dx.doi.org/10.1088/0029-5515/45/7/006 R. Kanno et al, ''Formation and healing of n = 1 magnetic islands in LHD equilibrium'', Nucl. Fusion '''45''' (2005) 588]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/45/7/006 R. Kanno et al, ''Formation and healing of n = 1 magnetic islands in LHD equilibrium'', Nucl. Fusion '''45''' (2005) 588]</ref>
	Active control of islands by external means - in particular, Electron Cyclotron Heating and Current Drive - is also possible (cf. the 'Seek and destroy' technique, under development <ref>[http://www.rijnhuizen.nl/en/node/195 Seek and Destroy System for magnetic island control]</ref>).		Active control of islands by external means - in particular, Electron Cyclotron Heating and Current Drive - is also possible (cf. the 'Seek and destroy' technique, under development <ref>[http://www.rijnhuizen.nl/en/node/195 Seek and Destroy System for magnetic island control]</ref>
			<ref>[http://dx.doi.org/10.1088/0029-5515/51/4/043007 B. Ayten et al., ''Modelling of tearing mode suppression experiments in TEXTOR based on the generalized Rutherford equation'', Nucl. Fusion '''51''' (2011) 043007]</ref>).

	== See also ==		== See also ==

Admin: /* Island birth */

2011-02-02T13:48:26Z

Island birth

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	The rupture of the assumed initial topology of toroidally nested flux surfaces needed to produce the island requires the reconnection of magnetic field lines, which can only occur with finite resistivity.		The rupture of the assumed initial topology of toroidally nested flux surfaces needed to produce the island requires the reconnection of magnetic field lines, which can only occur with finite resistivity.
	<ref>[http://dx.doi.org/10.1088/0029-5515/49/10/104025 F.L. Waelbroeck, ''Theory and observations of magnetic islands'', Nucl. Fusion '''49''' (2009) 104025]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/49/10/104025 F.L. Waelbroeck, ''Theory and observations of magnetic islands'', Nucl. Fusion '''49''' (2009) 104025]</ref>
			[[Stellarator]]s may have a vacuum magnetic field structure that already contains some islands (so-called 'natural islands').
			Since these are completely determined by the external magnetic field, they are static.

	== Island growth and saturation ==		== Island growth and saturation ==

Admin at 07:32, 16 December 2010

2010-12-16T07:32:51Z

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	It is generally assumed that the temperature is rapidly equilibrated along the magnetic field lines inside the island, so that radial transport is effectively short-circuited across the islands, decreasing the effective size of the main plasma.		It is generally assumed that the temperature is rapidly equilibrated along the magnetic field lines inside the island, so that radial transport is effectively short-circuited across the islands, decreasing the effective size of the main plasma.
	<ref>[http://dx.doi.org/10.1088/0029-5515/39/12/302 ITER Physics Expert Group on Confinement and Transport et al, ''Chapter 2: Plasma confinement and transport'', Nucl. Fusion '''39''' (1999) 2175-2249 ]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/39/12/302 ITER Physics Expert Group on Confinement and Transport et al, ''Chapter 2: Plasma confinement and transport'', Nucl. Fusion '''39''' (1999) 2175-2249 ]</ref>
	However, it is possible to ~~quantify~~ this statement somewhat by taking into account the ratio between parallel and perpendicular transport within an island.		However, it is possible to qualify this statement somewhat by taking into account the ratio between parallel and perpendicular transport within an island.
	<ref>[http://dx.doi.org/10.1088/0029-5515/33/8/I03 B.Ph. van Milligen, A.C.A.P. van Lammeren, N.J. Lopes Cardozo, F.C. Schüller, and M. Verreck, ''Gradients of electron temperature and density across m=2 islands in RTP'', Nucl. Fusion '''33''' (1993) 1119]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/33/8/I03 B.Ph. van Milligen, A.C.A.P. van Lammeren, N.J. Lopes Cardozo, F.C. Schüller, and M. Verreck, ''Gradients of electron temperature and density across m=2 islands in RTP'', Nucl. Fusion '''33''' (1993) 1119]</ref>

203.230.125.100: /* Transport effects */

2010-12-16T05:38:12Z

Transport effects

← Older revision		Revision as of 07:38, 16 December 2010
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	It is generally assumed that the temperature is rapidly equilibrated along the magnetic field lines inside the island, so that radial transport is effectively short-circuited across the islands, decreasing the effective size of the main plasma.		It is generally assumed that the temperature is rapidly equilibrated along the magnetic field lines inside the island, so that radial transport is effectively short-circuited across the islands, decreasing the effective size of the main plasma.
	<ref>[http://dx.doi.org/10.1088/0029-5515/39/12/302 ITER Physics Expert Group on Confinement and Transport et al, ''Chapter 2: Plasma confinement and transport'', Nucl. Fusion '''39''' (1999) 2175-2249 ]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/39/12/302 ITER Physics Expert Group on Confinement and Transport et al, ''Chapter 2: Plasma confinement and transport'', Nucl. Fusion '''39''' (1999) 2175-2249 ]</ref>
	However, is is possible to ~~qualify~~ this statement somewhat by taking into account the ratio between parallel and perpendicular transport within an island.		However, it is possible to quantify this statement somewhat by taking into account the ratio between parallel and perpendicular transport within an island.
	<ref>[http://dx.doi.org/10.1088/0029-5515/33/8/I03 B.Ph. van Milligen, A.C.A.P. van Lammeren, N.J. Lopes Cardozo, F.C. Schüller, and M. Verreck, ''Gradients of electron temperature and density across m=2 islands in RTP'', Nucl. Fusion '''33''' (1993) 1119]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/33/8/I03 B.Ph. van Milligen, A.C.A.P. van Lammeren, N.J. Lopes Cardozo, F.C. Schüller, and M. Verreck, ''Gradients of electron temperature and density across m=2 islands in RTP'', Nucl. Fusion '''33''' (1993) 1119]</ref>

← Older revision		Revision as of 09:19, 6 April 2023
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	== See also ==		== See also ==
	* [[MHD equilibrium]]		* [[MHD equilibrium]]
			* [[Island Divertor]]

	== References ==		== References ==
	<references />		<references />

← Older revision		Revision as of 11:37, 14 December 2014
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	In the context of magnetic confinement fusion, the basic magnetic field configuration consists of toroidally nested [[Flux surface\|flux surfaces]], while each flux surface is characterised by a certain value of the [[Rotational transform\|rotational transform]] or safety factor ''q''. Magnetic islands can appear at flux surfaces with a rational value of the safety factor ''q = m/n''.		In the context of magnetic confinement fusion, the basic magnetic field configuration consists of toroidally nested [[Flux surface\|flux surfaces]], while each flux surface is characterised by a certain value of the [[Rotational transform\|rotational transform]] or safety factor ''q''. Magnetic islands can appear at flux surfaces with a rational value of the safety factor ''q = m/n''.
	<ref>~~[http://dx.doi.org/10.1051/anphys:2004001~~ J.H. Misguich, J.-D. Reuss, D. Constantinescu, G. Steinbrecher, M. Vlad, F. Spineanu, B. Weyssow, R. Balescu, ''Noble internal transport barriers and radial subdiffusion of toroidal magnetic lines'', Ann. Phys. Fr. '''28''' (2003) 1]</ref>		<ref>J.H. Misguich, J.-D. Reuss, D. Constantinescu, G. Steinbrecher, M. Vlad, F. Spineanu, B. Weyssow, R. Balescu, ''Noble internal transport barriers and radial subdiffusion of toroidal magnetic lines'', [[doi:10.1051/anphys:2004001\|Ann. Phys. Fr. '''28''' (2003) 1]]</ref>
	Subsidiary islands can appear within an island.		Subsidiary islands can appear within an island.

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	The rupture of the assumed initial topology of toroidally nested flux surfaces needed to produce the island requires the reconnection of magnetic field lines, which can only occur with finite resistivity.		The rupture of the assumed initial topology of toroidally nested flux surfaces needed to produce the island requires the reconnection of magnetic field lines, which can only occur with finite resistivity.
	<ref>~~[http://dx.doi.org/10.1088/0029-5515/49/10/104025~~ F.L. Waelbroeck, ''Theory and observations of magnetic islands'', Nucl. Fusion '''49''' (2009) 104025]</ref>		<ref>F.L. Waelbroeck, ''Theory and observations of magnetic islands'', [[doi:10.1088/0029-5515/49/10/104025\|Nucl. Fusion '''49''' (2009) 104025]]</ref>
	[[Stellarator]]s may have a vacuum magnetic field structure that already contains some islands (so-called 'natural islands').		[[Stellarator]]s may have a vacuum magnetic field structure that already contains some islands (so-called 'natural islands').
	Since these are completely determined by the external magnetic field, they are static.		Since these are completely determined by the external magnetic field, they are static.
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	The prediction of the non-linear saturated state of islands is the goal of [[Neoclassical transport\|Neoclassical]] Tearing Mode (NTM) theory.		The prediction of the non-linear saturated state of islands is the goal of [[Neoclassical transport\|Neoclassical]] Tearing Mode (NTM) theory.
	This theory has been developed to a considerable level of sophistication, although discrepancies with experimental observations remain.		This theory has been developed to a considerable level of sophistication, although discrepancies with experimental observations remain.
	<ref>~~[http://link.aip.org/link/?PHPAEN/12/080703/1~~ H. Lütjens and J.-F. Luciani, ''Saturation levels of neoclassical tearing modes in International Thermonuclear Experimental Reactor plasmas'', Phys. Plasmas '''12''' (2005) 080703]</ref>		<ref>H. Lütjens and J.-F. Luciani, ''Saturation levels of neoclassical tearing modes in International Thermonuclear Experimental Reactor plasmas'', [[doi:10.1063/1.2001667\|Phys. Plasmas '''12''' (2005) 080703]]</ref>

	== Island rotation ==		== Island rotation ==
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	The detection of such modes is possible by measuring perturbations of the magnetic field, or the electron density, temperature, or pressure.		The detection of such modes is possible by measuring perturbations of the magnetic field, or the electron density, temperature, or pressure.
	If the ambient magnetic field (produced by external coils) has an appropriate structure, the island can also lock onto that structure.		If the ambient magnetic field (produced by external coils) has an appropriate structure, the island can also lock onto that structure.
	<ref>~~[http://link.aps.org/doi/10.1103/PhysRevLett.78.1703~~ F.L. Waelbroeck and R. Fitzpatrick, ''Rotation and Locking of Magnetic Islands'', Phys. Rev. Lett. '''78''' (1997) 1703–1706]</ref>		<ref>F.L. Waelbroeck and R. Fitzpatrick, ''Rotation and Locking of Magnetic Islands'', [[doi:10.1103/PhysRevLett.78.1703\|Phys. Rev. Lett. '''78''' (1997) 1703–1706]]</ref>
	Locked islands often lead to a [[Disruption\|disruption]] (complete loss of confinement) in [[Tokamak\|tokamaks]].		Locked islands often lead to a [[Disruption\|disruption]] (complete loss of confinement) in [[Tokamak\|tokamaks]].

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	It is generally assumed that the temperature is rapidly equilibrated along the magnetic field lines inside the island, so that radial transport is effectively short-circuited across the islands, decreasing the effective size of the main plasma.		It is generally assumed that the temperature is rapidly equilibrated along the magnetic field lines inside the island, so that radial transport is effectively short-circuited across the islands, decreasing the effective size of the main plasma.
	<ref>~~[http://dx.doi.org/10.1088/0029-5515/39/12/302~~ ITER Physics Expert Group on Confinement and Transport et al, ''Chapter 2: Plasma confinement and transport'', Nucl. Fusion '''39''' (1999) 2175-2249 ]</ref>		<ref>ITER Physics Expert Group on Confinement and Transport et al, ''Chapter 2: Plasma confinement and transport'', [[doi:10.1088/0029-5515/39/12/302\|Nucl. Fusion '''39''' (1999) 2175-2249]]</ref>
	However, it is possible to qualify this statement somewhat by taking into account the ratio between parallel and perpendicular transport within an island.		However, it is possible to qualify this statement somewhat by taking into account the ratio between parallel and perpendicular transport within an island.
	<ref>~~[http://dx.doi.org/10.1088/0029-5515/33/8/I03~~ B.Ph. van Milligen, A.C.A.P. van Lammeren, N.J. Lopes Cardozo, F.C. Schüller, and M. Verreck, ''Gradients of electron temperature and density across m=2 islands in RTP'', Nucl. Fusion '''33''' (1993) 1119]</ref>		<ref>B.Ph. van Milligen, A.C.A.P. van Lammeren, N.J. Lopes Cardozo, F.C. Schüller, and M. Verreck, ''Gradients of electron temperature and density across m=2 islands in RTP'', [[doi:10.1088/0029-5515/33/8/I03\|Nucl. Fusion '''33''' (1993) 1119]]</ref>

	The interaction of neighbouring island chains causes the magnetic field to become stochastic (according to the Chirikov criterion <ref>~~[http://dx.doi.org/10.1016/0370-1573(79)90023-1~~ B.V. Chirikov, ''A universal instability of many-dimensional oscillator systems'', Phys. Rep. '''52''', Issue 5 (1979) 263]</ref>), resulting in enhanced (anomalous) radial transport.		The interaction of neighbouring island chains causes the magnetic field to become stochastic (according to the Chirikov criterion <ref>B.V. Chirikov, ''A universal instability of many-dimensional oscillator systems'', [[doi:10.1016/0370-1573(79)90023-1\|Phys. Rep. '''52''', Issue 5 (1979) 263]]</ref>), resulting in enhanced (anomalous) radial transport.
	<ref>C.W. Horton, Y.H. Ichikawa, ''Chaos and structures in nonlinear plasmas'', World Scientific, 1996 ISBN 9789810226367</ref>		<ref>C.W. Horton, Y.H. Ichikawa, ''Chaos and structures in nonlinear plasmas'', World Scientific, 1996 ISBN 9789810226367</ref>

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	Island control is possible by tailoring the ''q''-profile, external magnetic fields,		Island control is possible by tailoring the ''q''-profile, external magnetic fields,
	<ref>~~[http://dx.doi.org/10.1088/0741-3335/44/7/323~~ S.R. Hudson et al, ''Free-boundary full-pressure island healing in stellarator equilibria: coil-healing'', Plasma Phys. Control. Fusion '''44''' (2002) 1377]</ref>		<ref>S.R. Hudson et al, ''Free-boundary full-pressure island healing in stellarator equilibria: coil-healing'', [[doi:10.1088/0741-3335/44/7/323\|Plasma Phys. Control. Fusion '''44''' (2002) 1377]]</ref>
	and the pressure profile, or by spinning up the plasma.		and the pressure profile, or by spinning up the plasma.
	<ref>~~[http://dx.doi.org/10.1088/0741-3335/45/12A/012~~ H. Zohm et al,''MHD limits to tokamak operation and their control'', Plasma Phys. Control. Fusion '''45''' (2003) A163]</ref>		<ref>H. Zohm et al,''MHD limits to tokamak operation and their control'', [[doi:10.1088/0741-3335/45/12A/012\|Plasma Phys. Control. Fusion '''45''' (2003) A163]]</ref>
	Pressure effects can lead to 'island healing'.		Pressure effects can lead to 'island healing'.
	<ref>~~[http://dx.doi.org/10.1088/0029-5515/45/7/006~~ R. Kanno et al, ''Formation and healing of n = 1 magnetic islands in LHD equilibrium'', Nucl. Fusion '''45''' (2005) 588]</ref>		<ref>R. Kanno et al, ''Formation and healing of n = 1 magnetic islands in LHD equilibrium'', [[doi:10.1088/0029-5515/45/7/006\|Nucl. Fusion '''45''' (2005) 588]]</ref>
	Active control of islands by external means - in particular, Electron Cyclotron Heating and Current Drive - is also possible.		Active control of islands by external means - in particular, Electron Cyclotron Heating and Current Drive - is also possible.
	<ref>[http://www.rijnhuizen.nl/en/node/195 Seek and Destroy System for magnetic island control]</ref>		<ref>[http://www.rijnhuizen.nl/en/node/195 Seek and Destroy System for magnetic island control]</ref>
	<ref>~~[http://dx.doi.org/10.1088/0029-5515/49/5/055006~~ A. Isayama et al, ''Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U'', Nucl. Fusion '''49''' (2009) 055006]</ref>		<ref>A. Isayama et al, ''Neoclassical tearing mode control using electron cyclotron current drive and magnetic island evolution in JT-60U'', [[doi:10.1088/0029-5515/49/5/055006\|Nucl. Fusion '''49''' (2009) 055006]]</ref>
	<ref>~~[http://dx.doi.org/10.1088/0029-5515/51/4/043007~~ B. Ayten et al., ''Modelling of tearing mode suppression experiments in TEXTOR based on the generalized Rutherford equation'', Nucl. Fusion '''51''' (2011) 043007]</ref>		<ref>B. Ayten et al., ''Modelling of tearing mode suppression experiments in TEXTOR based on the generalized Rutherford equation'', [[doi:10.1088/0029-5515/51/4/043007\|Nucl. Fusion '''51''' (2011) 043007]]</ref>

	== See also ==		== See also ==