TJ-II:Instabilities - Revision history

Admin: Updated reference links

2018-04-03T15:45:16Z

Updated reference links

← Older revision		Revision as of 17:45, 3 April 2018
Line 4:		Line 4:

	The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global [[Alfvén eigenmodes]] related to the low-order resonance n/m = 3/2.		The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global [[Alfvén eigenmodes]] related to the low-order resonance n/m = 3/2.
	<ref>~~[http://www.new.ans.org/pubs/journals/fst/a_1283~~ R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>		<ref>R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', [http://www.new.ans.org/pubs/journals/fst/a_1283 Fusion Science and Technology '''51''', 20 (2007)]</ref>
	<ref>~~[http://dx.doi.org/10.1088/0029-5515/51/3/033001~~ R. Jiménez-Gómez, A. Könies, E. Ascasíbar, et al, ''Alfvén eigenmodes measured in the TJ-II stellarator'', Nucl. Fusion '''51''' (2011) 033001 ]</ref>		<ref>R. Jiménez-Gómez, A. Könies, E. Ascasíbar, et al, ''Alfvén eigenmodes measured in the TJ-II stellarator'', [[doi:10.1088/0029-5515/51/3/033001\|Nucl. Fusion '''51''' (2011) 033001]]</ref>

	== ELM-like modes ==		== ELM-like modes ==

	ELM-like activity has been observed in plasmas with a stored energy above 1 kJ. The plasma is observed to develop bursts of magnetic activity (seen in Mirnov coil signals) which are followed by a large and distinct spike in the H<sub>α</sub> signal. An increase in electrostatic and magnetic fluctuations at the plasma edge and a cold pulse towards the plasma centre are also characteristic of these events. In addition, the electron temperature profile locally flattens at the plasma radius where the temperature is in the range 100-200 eV. This flattening can be explained in terms of enhanced electron heat conductivity. Between ELM-like events the electromagnetic turbulence at the edge decreases and the ''T<sub>e</sub>'' profiles recover their former shapes. This activity is probably triggered by a resonant m = 2, n = 3 mode.		ELM-like activity has been observed in plasmas with a stored energy above 1 kJ. The plasma is observed to develop bursts of magnetic activity (seen in Mirnov coil signals) which are followed by a large and distinct spike in the H<sub>α</sub> signal. An increase in electrostatic and magnetic fluctuations at the plasma edge and a cold pulse towards the plasma centre are also characteristic of these events. In addition, the electron temperature profile locally flattens at the plasma radius where the temperature is in the range 100-200 eV. This flattening can be explained in terms of enhanced electron heat conductivity. Between ELM-like events the electromagnetic turbulence at the edge decreases and the ''T<sub>e</sub>'' profiles recover their former shapes. This activity is probably triggered by a resonant m = 2, n = 3 mode.
	<ref>~~[http://dx.doi.org/10.1088/0029-5515/40/11/306~~ I. García-Cortés et al, ''Edge-localized-mode-like events in the TJ-II stellarator'', Nucl. Fusion '''40''' (2000) 1867-1874]</ref>		<ref>I. García-Cortés et al, ''Edge-localized-mode-like events in the TJ-II stellarator'', [[doi:10.1088/0029-5515/40/11/306\|Nucl. Fusion '''40''' (2000) 1867-1874]]</ref>
	<ref>~~[http://dx.doi.org/10.1088/0741-3335/48/5/002~~ J.A. Jiménez et al, ''Localized electromagnetic modes in MHD stable regime of the TJ-II Heliac'', Plasma Phys. Control. Fusion '''48''' (2006) 515-526]</ref>		<ref>J.A. Jiménez et al, ''Localized electromagnetic modes in MHD stable regime of the TJ-II Heliac'', [[doi:10.1088/0741-3335/48/5/002\|Plasma Phys. Control. Fusion '''48''' (2006) 515-526]]</ref>

	== Influence of the magnetic well ==		== Influence of the magnetic well ==
Line 17:		Line 17:
	MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "[[Magnetic well\|magnetic well]]". This idea is supported by magnetic well scan experiments in TJ-II.		MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "[[Magnetic well\|magnetic well]]". This idea is supported by magnetic well scan experiments in TJ-II.
	The level of fluctuations, the degree of intermittency and the radial correlation of relevant quantities increase as the magnetic well is reduced.		The level of fluctuations, the degree of intermittency and the radial correlation of relevant quantities increase as the magnetic well is reduced.
	<ref>~~[http://dx.doi.org/10.1088/0741-3335/43/12A/324~~ C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>		<ref>C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', [[doi:10.1088/0741-3335/43/12A/324\|Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]]</ref>
	<ref>~~[http://link.aip.org/link/?PHPAEN/9/713/1~~ J. Castellano et al, ''Magnetic well and instability thresholds in the TJ-II stellarator'', Phys. Plasmas '''9''' (2002) 713]</ref>		<ref>J. Castellano et al, ''Magnetic well and instability thresholds in the TJ-II stellarator'', [[doi:10.1063/1.1430435\|Phys. Plasmas '''9''' (2002) 713]]</ref>

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

Admin at 09:10, 3 May 2012

2012-05-03T09:10:43Z

← Older revision		Revision as of 11:10, 3 May 2012
Line 5:		Line 5:
	The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global [[Alfvén eigenmodes]] related to the low-order resonance n/m = 3/2.		The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global [[Alfvén eigenmodes]] related to the low-order resonance n/m = 3/2.
	<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>		<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>
	<ref>[http://dx.doi.org/10.1088/0029-5515/51/3/~~032001~~ R. Jiménez-Gómez, A. Könies, E. Ascasíbar, et al, ''Alfvén eigenmodes measured in the TJ-II stellarator'', Nucl. Fusion '''51''' (2011) 033001 ]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/51/3/033001 R. Jiménez-Gómez, A. Könies, E. Ascasíbar, et al, ''Alfvén eigenmodes measured in the TJ-II stellarator'', Nucl. Fusion '''51''' (2011) 033001 ]</ref>

	== ELM-like modes ==		== ELM-like modes ==

Admin at 18:12, 8 August 2011

2011-08-08T18:12:06Z

← Older revision		Revision as of 20:12, 8 August 2011
Line 1:		Line 1:
	At [[TJ-II]], a number of studies have been performed to analyse and understand the various instabilities occurring in fusion-grade plasmas.		At [[TJ-II]], a number of studies have been performed to analyse and understand the various [[Plasma instability\|instabilities]] occurring in fusion-grade plasmas.

	== MHD and Alfvén modes ==		== MHD and Alfvén modes ==

Admin: /* MHD and Alfvén modes */

2011-06-30T18:33:35Z

MHD and Alfvén modes

← Older revision		Revision as of 20:33, 30 June 2011
Line 5:		Line 5:
	The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global [[Alfvén eigenmodes]] related to the low-order resonance n/m = 3/2.		The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global [[Alfvén eigenmodes]] related to the low-order resonance n/m = 3/2.
	<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>		<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>
			<ref>[http://dx.doi.org/10.1088/0029-5515/51/3/032001 R. Jiménez-Gómez, A. Könies, E. Ascasíbar, et al, ''Alfvén eigenmodes measured in the TJ-II stellarator'', Nucl. Fusion '''51''' (2011) 033001 ]</ref>

	== ELM-like modes ==		== ELM-like modes ==

Admin: /* MHD and Alfvén modes */

2011-06-30T18:26:24Z

MHD and Alfvén modes

← Older revision		Revision as of 20:26, 30 June 2011
Line 3:		Line 3:
	== MHD and Alfvén modes ==		== MHD and Alfvén modes ==

	The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global Alfvén eigenmodes related to the low-order resonance n/m = 3/2.		The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global [[Alfvén eigenmodes]] related to the low-order resonance n/m = 3/2.
	<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>		<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>

Admin: Reverted edits by Otihizuv (Talk) to last revision by Admin

2010-11-24T11:22:22Z

Reverted edits by Otihizuv (Talk) to last revision by Admin

Otihizuv at 08:46, 24 November 2010

2010-11-24T08:46:25Z

Admin: /* Influence of the magnetic well */

2009-08-23T17:00:21Z

Influence of the magnetic well

← Older revision		Revision as of 19:00, 23 August 2009
Line 15:		Line 15:

	MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "[[Magnetic well\|magnetic well]]". This idea is supported by magnetic well scan experiments in TJ-II.		MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "[[Magnetic well\|magnetic well]]". This idea is supported by magnetic well scan experiments in TJ-II.
			The level of fluctuations, the degree of intermittency and the radial correlation of relevant quantities increase as the magnetic well is reduced.
	<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>		<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>
			<ref>[http://link.aip.org/link/?PHPAEN/9/713/1 J. Castellano et al, ''Magnetic well and instability thresholds in the TJ-II stellarator'', Phys. Plasmas '''9''' (2002) 713]</ref>

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

Admin: /* Influence of the magnetic well */

2009-08-09T10:36:38Z

Influence of the magnetic well

← Older revision		Revision as of 12:36, 9 August 2009
Line 14:		Line 14:
	== Influence of the magnetic well ==		== Influence of the magnetic well ==

	MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "magnetic well". This idea is supported by magnetic well scan experiments in TJ-II.		MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "[[Magnetic well\|magnetic well]]". This idea is supported by magnetic well scan experiments in TJ-II.
	<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>		<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>

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

Admin at 10:29, 9 August 2009

2009-08-09T10:29:10Z

← Older revision		Revision as of 12:29, 9 August 2009
Line 8:		Line 8:
	== ELM-like modes ==		== ELM-like modes ==

	ELM-like activity has been observed in plasmas with a stored energy above 1 kJ. The plasma is observed to develop bursts of magnetic activity (seen in Mirnov coil signals) which are followed by a large and distinct spike in the H<sub>α</sub> signal. An increase in electrostatic and magnetic fluctuations at the plasma edge and a cold pulse towards the plasma centre are also characteristic of these events. In addition, the electron temperature profile locally flattens at the plasma radius where the temperature is in the range 100-200 eV. This flattening can be explained in terms of enhanced electron heat conductivity. Between ELM-like events the electromagnetic turbulence at the edge decreases and the Te profiles recover their former shapes. This activity is probably triggered by a resonant m = 2, n = 3 mode.		ELM-like activity has been observed in plasmas with a stored energy above 1 kJ. The plasma is observed to develop bursts of magnetic activity (seen in Mirnov coil signals) which are followed by a large and distinct spike in the H<sub>α</sub> signal. An increase in electrostatic and magnetic fluctuations at the plasma edge and a cold pulse towards the plasma centre are also characteristic of these events. In addition, the electron temperature profile locally flattens at the plasma radius where the temperature is in the range 100-200 eV. This flattening can be explained in terms of enhanced electron heat conductivity. Between ELM-like events the electromagnetic turbulence at the edge decreases and the ''T<sub>e</sub>'' profiles recover their former shapes. This activity is probably triggered by a resonant m = 2, n = 3 mode.
	<ref>[http://dx.doi.org/10.1088/0029-5515/40/11/306 I. García-Cortés et al, ''Edge-localized-mode-like events in the TJ-II stellarator'', Nucl. Fusion '''40''' (2000) 1867-1874]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/40/11/306 I. García-Cortés et al, ''Edge-localized-mode-like events in the TJ-II stellarator'', Nucl. Fusion '''40''' (2000) 1867-1874]</ref>
	<ref>[http://dx.doi.org/10.1088/0741-3335/48/5/002 J.A. Jiménez et al, ''Localized electromagnetic modes in MHD stable regime of the TJ-II Heliac'', Plasma Phys. Control. Fusion '''48''' (2006) 515-526]</ref>		<ref>[http://dx.doi.org/10.1088/0741-3335/48/5/002 J.A. Jiménez et al, ''Localized electromagnetic modes in MHD stable regime of the TJ-II Heliac'', Plasma Phys. Control. Fusion '''48''' (2006) 515-526]</ref>
Line 14:		Line 14:
	== Influence of the magnetic well ==		== Influence of the magnetic well ==

	~~Instabilities~~ inside the plasma are ~~supposed to be~~ stabilized by ~~an increased~~ "magnetic well". This idea is supported by magnetic well scan experiments in TJ-II.		MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "magnetic well". This idea is supported by magnetic well scan experiments in TJ-II.
	<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>		<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>

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

← Older revision		Revision as of 13:22, 24 November 2010
Line 1:		Line 1:
	~~=[http://azysijogen.co.cc This Page Is Currently Under Construction And Will Be Available Shortly, Please Visit Reserve Copy Page]=~~
	At [[TJ-II]], a number of studies have been performed to analyse and understand the various instabilities occurring in fusion-grade plasmas.		At [[TJ-II]], a number of studies have been performed to analyse and understand the various instabilities occurring in fusion-grade plasmas.

	== MHD and Alfvén modes ==		== MHD and Alfvén modes ==

	The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10~~<~~sup~~>~~19~~<~~/sup~~>~~ m~~<~~sup~~>~~-3~~<~~/sup~~>~~ to 3 × 10~~<~~sup~~>~~19~~<~~/sup~~>~~ m~~<~~sup~~>~~-3~~<~~/sup~~>~~ and heated with on/off-axis electron cyclotron heating. They are good candidates for global Alfvén eigenmodes related to the low-order resonance n/m = 3/2.		The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global Alfvén eigenmodes related to the low-order resonance n/m = 3/2.
	~~<~~ref~~>~~[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]~~<~~/ref~~>~~		<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>

	== ELM-like modes ==		== ELM-like modes ==

	ELM-like activity has been observed in plasmas with a stored energy above 1 kJ. The plasma is observed to develop bursts of magnetic activity (seen in Mirnov coil signals) which are followed by a large and distinct spike in the H~~<~~sub&~~gt;&~~alpha;~~<~~/sub~~>~~ signal. An increase in electrostatic and magnetic fluctuations at the plasma edge and a cold pulse towards the plasma centre are also characteristic of these events. In addition, the electron temperature profile locally flattens at the plasma radius where the temperature is in the range 100-200 eV. This flattening can be explained in terms of enhanced electron heat conductivity. Between ELM-like events the electromagnetic turbulence at the edge decreases and the ''T~~<~~sub~~>~~e~~<~~/sub~~>~~'' profiles recover their former shapes. This activity is probably triggered by a resonant m = 2, n = 3 mode.		ELM-like activity has been observed in plasmas with a stored energy above 1 kJ. The plasma is observed to develop bursts of magnetic activity (seen in Mirnov coil signals) which are followed by a large and distinct spike in the H<sub>α</sub> signal. An increase in electrostatic and magnetic fluctuations at the plasma edge and a cold pulse towards the plasma centre are also characteristic of these events. In addition, the electron temperature profile locally flattens at the plasma radius where the temperature is in the range 100-200 eV. This flattening can be explained in terms of enhanced electron heat conductivity. Between ELM-like events the electromagnetic turbulence at the edge decreases and the ''T<sub>e</sub>'' profiles recover their former shapes. This activity is probably triggered by a resonant m = 2, n = 3 mode.
	~~<~~ref~~>~~[http://dx.doi.org/10.1088/0029-5515/40/11/306 I. García-Cortés et al, ''Edge-localized-mode-like events in the TJ-II stellarator'', Nucl. Fusion '''40''' (2000) 1867-1874]~~<~~/ref~~>~~		<ref>[http://dx.doi.org/10.1088/0029-5515/40/11/306 I. García-Cortés et al, ''Edge-localized-mode-like events in the TJ-II stellarator'', Nucl. Fusion '''40''' (2000) 1867-1874]</ref>
	~~<~~ref~~>~~[http://dx.doi.org/10.1088/0741-3335/48/5/002 J.A. Jiménez et al, ''Localized electromagnetic modes in MHD stable regime of the TJ-II Heliac'', Plasma Phys. Control. Fusion '''48''' (2006) 515-526]~~<~~/ref~~>~~		<ref>[http://dx.doi.org/10.1088/0741-3335/48/5/002 J.A. Jiménez et al, ''Localized electromagnetic modes in MHD stable regime of the TJ-II Heliac'', Plasma Phys. Control. Fusion '''48''' (2006) 515-526]</ref>

	== Influence of the magnetic well ==		== Influence of the magnetic well ==

	MHD theory predicts that instabilities inside the plasma are stabilized by increasing the ~~"~~[[Magnetic well\|magnetic well]]~~"~~. This idea is supported by magnetic well scan experiments in TJ-II.		MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "[[Magnetic well\|magnetic well]]". This idea is supported by magnetic well scan experiments in TJ-II.
	The level of fluctuations, the degree of intermittency and the radial correlation of relevant quantities increase as the magnetic well is reduced.		The level of fluctuations, the degree of intermittency and the radial correlation of relevant quantities increase as the magnetic well is reduced.
	~~<~~ref~~>~~[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]~~<~~/ref~~>~~		<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>
	~~<~~ref~~>~~[http://link.aip.org/link/?PHPAEN/9/713/1 J. Castellano et al, ''Magnetic well and instability thresholds in the TJ-II stellarator'', Phys. Plasmas '''9''' (2002) 713]~~<~~/ref~~>~~		<ref>[http://link.aip.org/link/?PHPAEN/9/713/1 J. Castellano et al, ''Magnetic well and instability thresholds in the TJ-II stellarator'', Phys. Plasmas '''9''' (2002) 713]</ref>

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

← Older revision		Revision as of 10:46, 24 November 2010
Line 1:		Line 1:
			=[http://azysijogen.co.cc This Page Is Currently Under Construction And Will Be Available Shortly, Please Visit Reserve Copy Page]=
	At [[TJ-II]], a number of studies have been performed to analyse and understand the various instabilities occurring in fusion-grade plasmas.		At [[TJ-II]], a number of studies have been performed to analyse and understand the various instabilities occurring in fusion-grade plasmas.

	== MHD and Alfvén modes ==		== MHD and Alfvén modes ==

	The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global Alfvén eigenmodes related to the low-order resonance n/m = 3/2.		The appearance of low-frequency Magneto-HydroDynamic (MHD) modes (some tens of kilohertz) in electron cyclotron heated plasmas depends on the rotational transform profile and the plasma density. In neutral beam injection plasmas, high-frequency modes (150- to 300-kHz) have been found in plasmas with line densities in the range 0.6 × 10<sup>19</sup> m<sup>-3</sup> to 3 × 10<sup>19</sup> m<sup>-3</sup> and heated with on/off-axis electron cyclotron heating. They are good candidates for global Alfvén eigenmodes related to the low-order resonance n/m = 3/2.
	<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>		<ref>[http://www.new.ans.org/pubs/journals/fst/a_1283 R. Jiménez-Gómez et al., ''Analysis of Magnetohydrodynamic Instabilities in TJ-II Plasmas'', Fusion Science and Technology '''51''', 20 (2007)]</ref>

	== ELM-like modes ==		== ELM-like modes ==

	ELM-like activity has been observed in plasmas with a stored energy above 1 kJ. The plasma is observed to develop bursts of magnetic activity (seen in Mirnov coil signals) which are followed by a large and distinct spike in the H<sub>α</sub> signal. An increase in electrostatic and magnetic fluctuations at the plasma edge and a cold pulse towards the plasma centre are also characteristic of these events. In addition, the electron temperature profile locally flattens at the plasma radius where the temperature is in the range 100-200 eV. This flattening can be explained in terms of enhanced electron heat conductivity. Between ELM-like events the electromagnetic turbulence at the edge decreases and the ''T<sub>e</sub>'' profiles recover their former shapes. This activity is probably triggered by a resonant m = 2, n = 3 mode.		ELM-like activity has been observed in plasmas with a stored energy above 1 kJ. The plasma is observed to develop bursts of magnetic activity (seen in Mirnov coil signals) which are followed by a large and distinct spike in the H<sub>&alpha;</sub> signal. An increase in electrostatic and magnetic fluctuations at the plasma edge and a cold pulse towards the plasma centre are also characteristic of these events. In addition, the electron temperature profile locally flattens at the plasma radius where the temperature is in the range 100-200 eV. This flattening can be explained in terms of enhanced electron heat conductivity. Between ELM-like events the electromagnetic turbulence at the edge decreases and the ''T<sub>e</sub>'' profiles recover their former shapes. This activity is probably triggered by a resonant m = 2, n = 3 mode.
	<ref>[http://dx.doi.org/10.1088/0029-5515/40/11/306 I. García-Cortés et al, ''Edge-localized-mode-like events in the TJ-II stellarator'', Nucl. Fusion '''40''' (2000) 1867-1874]</ref>		<ref>[http://dx.doi.org/10.1088/0029-5515/40/11/306 I. García-Cortés et al, ''Edge-localized-mode-like events in the TJ-II stellarator'', Nucl. Fusion '''40''' (2000) 1867-1874]</ref>
	<ref>[http://dx.doi.org/10.1088/0741-3335/48/5/002 J.A. Jiménez et al, ''Localized electromagnetic modes in MHD stable regime of the TJ-II Heliac'', Plasma Phys. Control. Fusion '''48''' (2006) 515-526]</ref>		<ref>[http://dx.doi.org/10.1088/0741-3335/48/5/002 J.A. Jiménez et al, ''Localized electromagnetic modes in MHD stable regime of the TJ-II Heliac'', Plasma Phys. Control. Fusion '''48''' (2006) 515-526]</ref>

	== Influence of the magnetic well ==		== Influence of the magnetic well ==

	MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "[[Magnetic well\|magnetic well]]". This idea is supported by magnetic well scan experiments in TJ-II.		MHD theory predicts that instabilities inside the plasma are stabilized by increasing the "[[Magnetic well\|magnetic well]]". This idea is supported by magnetic well scan experiments in TJ-II.
	The level of fluctuations, the degree of intermittency and the radial correlation of relevant quantities increase as the magnetic well is reduced.		The level of fluctuations, the degree of intermittency and the radial correlation of relevant quantities increase as the magnetic well is reduced.
	<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>		<ref>[http://dx.doi.org/10.1088/0741-3335/43/12A/324 C. Hidalgo et al, ''On the radial scale of fluctuations in the TJ-II stellarator'', Plasma Phys. Control. Fusion '''43''' (2001) A313-A321]</ref>
	<ref>[http://link.aip.org/link/?PHPAEN/9/713/1 J. Castellano et al, ''Magnetic well and instability thresholds in the TJ-II stellarator'', Phys. Plasmas '''9''' (2002) 713]</ref>		<ref>[http://link.aip.org/link/?PHPAEN/9/713/1 J. Castellano et al, ''Magnetic well and instability thresholds in the TJ-II stellarator'', Phys. Plasmas '''9''' (2002) 713]</ref>

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