H-mode - Revision history

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	When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state.		When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or [[L-mode]]) state to a high confinement (or H-mode) state.
	<ref>F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', [[doi:10.1103/PhysRevLett.53.1453\|Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]]</ref>		<ref>F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', [[doi:10.1103/PhysRevLett.53.1453\|Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]]</ref>
	In the H-mode, the [[Energy confinement time\|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more.		In the H-mode, the [[Energy confinement time\|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more.

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← Older revision		Revision as of 11:50, 16 July 2011
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	In ~~awe~~ of that ~~anwser! Really cool!~~		When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state.
			<ref>[http://link.aps.org/doi/10.1103/PhysRevLett.53.1453 F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]</ref>
			In the H-mode, the [[Energy confinement time\|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more.
			<ref>[http://dx.doi.org/10.1088/0741-3335/29/10A/320 M. Keilhacker, ''H-mode confinement in tokamaks'', Plasma Phys. Control. Fusion '''29''' (1987) 1401-1413]</ref>
			<ref>[http://efdasql.ipp.mpg.de/HmodePublic/ The International Global H-mode Confinement Database]</ref>
			H-mode profiles have a characteristic ''[[Pedestal\|edge pedestal]]''.

			== Physical mechanism ==

			This transport bifurcation is due to the suppression of turbulence in the edge plasma.
			There is substantial evidence that the suppression of turbulence is the consequence of the formation of a sheared flow layer and an associated edge radial electric field.
			The local suppression of turbulence leads to a reduction of transport and a steepening of the edge profiles.
			<ref>[http://dx.doi.org/10.1088/0741-3335/49/12B/S01 F. Wagner, ''A quarter-century of H-mode studies'', Plasma Phys. Control. Fusion '''49''' (2007) B1-B33]</ref>

			A variety of mechanisms can give rise to sheared flow, or favour its growth:
			* The main process for sheared flow generation is generation by the turbulence itself via the [[Reynolds stress]] mechanism. Simply put, transport generated by the fluctuations produces a radial current ''j<sub>r</sub>'' that spins up the plasma via the ''j'' × ''B'' [[:Wikipedia:Lorentz force\|Lorentz force]]. <ref>[http://dx.doi.org/10.1063/1.859681 P.H. Diamond and Y.-B. Kim, ''Theory of mean poloidal flow generation by turbulence'', Phys. Fluids B '''3''' (1991) 1626]</ref> <ref>[http://dx.doi.org/10.1088/0741-3335/43/10/308 S.B. Korsholm et al, ''Reynolds stress and shear flow generation'', Plasma Phys. Control. Fusion '''43''' (2001) 1377-1395]</ref>
			* This radial current can also actively be produced by electrode biasing. <ref>[http://link.aps.org/doi/10.1103/PhysRevLett.63.2365 R.J. Taylor et al, ''H-mode behavior induced by cross-field currents in a tokamak'', Phys. Rev. Lett. '''63''' (1989) 2365-2368]</ref>
			* Sheared flow may be favoured by reduced viscous damping, which might explain the dependence on rational surfaces observed in the stellarator W7-AS. <ref>[http://dx.doi.org/10.1088/0741-3335/42/7/306 H. Wobig and J. Kisslinger, ''Viscous damping of rotation in Wendelstein 7-AS'', Plasma Phys. Control. Fusion '''42''' (2000) 823-841]</ref>
			* Sheared flow can also be generated by external momentum input.

			The details of the feedback mechanism between turbulence and sheared flow are the subject of ongoing studies.
			<ref>[http://link.aps.org/doi/10.1103/PhysRevLett.72.2565 P.H. Diamond et al, ''Self-Regulating Shear Flow Turbulence: A Paradigm for the L to H Transition'', Phys. Rev. Lett. '''72''' (1994) 2565 - 2568]</ref>
			<ref>[http://link.aip.org/link/?PHPAEN/16/012504/1 M.A. Malkov and P.H. Diamond, ''Weak hysteresis in a simplified model of the L-H transition'', Phys. Plasmas '''16''' (2009) 012504]</ref>

			In summary, the H-mode is the consequence of a self-organizing process in the plasma.
			The mechanism is probably closely related to the mechanism for forming an [[Internal Transport Barrier]].

			== See also ==

			* [[Edge Localized Modes]]

			== References ==
			<references />

190.11.182.2: YyEvfMjtAzVHvjVdQGQ

2011-07-16T09:15:50Z

YyEvfMjtAzVHvjVdQGQ

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	~~Knoewldge wants to be free, just like these articles~~!		In awe of that anwser! Really cool!

112.184.203.66: pszUZdvJxGwEV

2011-07-16T08:43:36Z

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	~~Ppl~~ like ~~you get all the brains. I just get to say thnaks for he answer.~~		Knoewldge wants to be free, just like these articles!

174.0.68.59: HblvBRjHZI

2011-07-16T06:18:49Z

HblvBRjHZI

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	~~What a joy~~ to ~~find such clear tihnikng~~. ~~Thanks for posting!~~		Ppl like you get all the brains. I just get to say thnaks for he answer.

160.252.82.29: rmCnCVRlGBoJeG

2011-07-16T05:39:48Z

rmCnCVRlGBoJeG

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	What ~~an awemose way~~ to ~~explain thisnow I know everything~~!		What a joy to find such clear tihnikng. Thanks for posting!

86.28.210.250: plODGITDapSclxgXNF

2011-07-16T05:01:33Z

plODGITDapSclxgXNF

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	~~That's not just the best aneswr. It's the bestest answer~~!		What an awemose way to explain thisnow I know everything!

200.158.66.180: zpwSJKrGQrk

2011-07-16T04:42:51Z

zpwSJKrGQrk

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	~~Well mcaaaidma nuts, how about that~~.		That's not just the best aneswr. It's the bestest answer!

← Older revision		Revision as of 15:38, 3 April 2018
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	When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state.		When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state.
	<ref>F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', [~~http~~:~~//link.aps.org/doi/~~10.1103/PhysRevLett.53.1453 Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]</ref>		<ref>F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', [[doi:10.1103/PhysRevLett.53.1453\|Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]]</ref>
	In the H-mode, the [[Energy confinement time\|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more.		In the H-mode, the [[Energy confinement time\|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more.
	<ref>M. Keilhacker, ''H-mode confinement in tokamaks'', [[doi:10.1088/0741-3335/29/10A/320\|Plasma Phys. Control. Fusion '''29''' (1987) 1401-1413]]</ref>		<ref>M. Keilhacker, ''H-mode confinement in tokamaks'', [[doi:10.1088/0741-3335/29/10A/320\|Plasma Phys. Control. Fusion '''29''' (1987) 1401-1413]]</ref>
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	A variety of mechanisms can give rise to sheared flow, or favour its growth:		A variety of mechanisms can give rise to sheared flow, or favour its growth:
	* The main process for sheared flow generation is generation by the turbulence itself via the [[Reynolds stress]] mechanism. Simply put, transport generated by the fluctuations produces a radial current ''j<sub>r</sub>'' that spins up the plasma via the ''j'' × ''B'' [[:Wikipedia:Lorentz force\|Lorentz force]]. <ref>P.H. Diamond and Y.-B. Kim, ''Theory of mean poloidal flow generation by turbulence'', [[doi:10.1063/1.859681\|Phys. Fluids B '''3''' (1991) 1626]]</ref> <ref>S.B. Korsholm et al, ''Reynolds stress and shear flow generation'', [[doi:10.1088/0741-3335/43/10/308\|Plasma Phys. Control. Fusion '''43''' (2001) 1377-1395]]</ref>		* The main process for sheared flow generation is generation by the turbulence itself via the [[Reynolds stress]] mechanism. Simply put, transport generated by the fluctuations produces a radial current ''j<sub>r</sub>'' that spins up the plasma via the ''j'' × ''B'' [[:Wikipedia:Lorentz force\|Lorentz force]]. <ref>P.H. Diamond and Y.-B. Kim, ''Theory of mean poloidal flow generation by turbulence'', [[doi:10.1063/1.859681\|Phys. Fluids B '''3''' (1991) 1626]]</ref> <ref>S.B. Korsholm et al, ''Reynolds stress and shear flow generation'', [[doi:10.1088/0741-3335/43/10/308\|Plasma Phys. Control. Fusion '''43''' (2001) 1377-1395]]</ref>
	* This radial current can also actively be produced by electrode biasing. <ref>R.J. Taylor et al, ''H-mode behavior induced by cross-field currents in a tokamak'', [~~http~~:~~//link.aps.org/doi/~~10.1103/PhysRevLett.63.2365 Phys. Rev. Lett. '''63''' (1989) 2365-2368]</ref>		* This radial current can also actively be produced by electrode biasing. <ref>R.J. Taylor et al, ''H-mode behavior induced by cross-field currents in a tokamak'', [[doi:10.1103/PhysRevLett.63.2365\|Phys. Rev. Lett. '''63''' (1989) 2365-2368]]</ref>
	* Sheared flow may be favoured by reduced viscous damping, which might explain the dependence on rational surfaces observed in the stellarator W7-AS. <ref>H. Wobig and J. Kisslinger, ''Viscous damping of rotation in Wendelstein 7-AS'', [[doi:10.1088/0741-3335/42/7/306\|Plasma Phys. Control. Fusion '''42''' (2000) 823-841]]</ref>		* Sheared flow may be favoured by reduced viscous damping, which might explain the dependence on rational surfaces observed in the stellarator W7-AS. <ref>H. Wobig and J. Kisslinger, ''Viscous damping of rotation in Wendelstein 7-AS'', [[doi:10.1088/0741-3335/42/7/306\|Plasma Phys. Control. Fusion '''42''' (2000) 823-841]]</ref>
	* Sheared flow can also be generated by external momentum input.		* Sheared flow can also be generated by external momentum input.

	The details of the feedback mechanism between turbulence and sheared flow are the subject of ongoing studies.		The details of the feedback mechanism between turbulence and sheared flow are the subject of ongoing studies.
	<ref>P.H. Diamond et al, ''Self-Regulating Shear Flow Turbulence: A Paradigm for the L to H Transition'', [~~http~~:~~//link.aps.org/doi/~~10.1103/PhysRevLett.72.2565 Phys. Rev. Lett. '''72''' (1994) 2565 - 2568]</ref>		<ref>P.H. Diamond et al, ''Self-Regulating Shear Flow Turbulence: A Paradigm for the L to H Transition'', [[doi:10.1103/PhysRevLett.72.2565\|Phys. Rev. Lett. '''72''' (1994) 2565 - 2568]]</ref>
	<ref>M.A. Malkov and P.H. Diamond, ''Weak hysteresis in a simplified model of the L-H transition'', [~~http~~:~~//link.aip~~.~~org/link/?PHPAEN/16/012504~~/1 Phys. Plasmas '''16''' (2009) 012504]</ref>		<ref>M.A. Malkov and P.H. Diamond, ''Weak hysteresis in a simplified model of the L-H transition'', [[doi:10.1063/1.3062834\|Phys. Plasmas '''16''' (2009) 012504]]</ref>

	In summary, the H-mode is the consequence of a self-organizing process in the plasma.		In summary, the H-mode is the consequence of a self-organizing process in the plasma.

← Older revision		Revision as of 17:17, 5 December 2015
Line 1:		Line 1:
	When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state.		When a magnetically confined plasma is heated strongly and a threshold heating power level is exceeded, it may spontaneously transition from a low confinement (or L-mode) state to a high confinement (or H-mode) state.
	<ref>~~[http://link.aps.org/doi/10.1103/PhysRevLett.53.1453~~ F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]</ref>		<ref>F. Wagner et al, ''Development of an Edge Transport Barrier at the H-Mode Transition of ASDEX'', [http://link.aps.org/doi/10.1103/PhysRevLett.53.1453 Phys. Rev. Lett. '''53''' (1984) 1453 - 1456]</ref>
	In the H-mode, the [[Energy confinement time\|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more.		In the H-mode, the [[Energy confinement time\|energy confinement time]] is significantly enhanced, i.e., typically by a factor of 2 or more.
	<ref>[~~http~~:~~//dx.doi.org/~~10.1088/0741-3335/29/10A/320 M. ~~Keilhacker~~, ''H-mode ~~confinement in tokamaks~~'', Plasma Phys. Control. Fusion '''29''' (~~1987~~) ~~1401-1413~~]</ref>		<ref>M. Keilhacker, ''H-mode confinement in tokamaks'', [[doi:10.1088/0741-3335/29/10A/320\|Plasma Phys. Control. Fusion '''29''' (1987) 1401-1413]]</ref>
			<ref>F. Wagner et al., ''H-mode of W7-AS stellarator'', [[doi:10.1088/0741-3335/36/7A/006\|Plasma Phys. Control. Fusion '''36''' (1994) A61]]</ref>
	<ref>[http://efdasql.ipp.mpg.de/HmodePublic/ The International Global H-mode Confinement Database]</ref>		<ref>[http://efdasql.ipp.mpg.de/HmodePublic/ The International Global H-mode Confinement Database]</ref>
	H-mode profiles have a characteristic ''[[Pedestal\|edge pedestal]]''.		H-mode profiles have a characteristic ''[[Pedestal\|edge pedestal]]''.
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	There is substantial evidence that the suppression of turbulence is the consequence of the formation of a sheared flow layer and an associated edge radial electric field.		There is substantial evidence that the suppression of turbulence is the consequence of the formation of a sheared flow layer and an associated edge radial electric field.
	The local suppression of turbulence leads to a reduction of transport and a steepening of the edge profiles.		The local suppression of turbulence leads to a reduction of transport and a steepening of the edge profiles.
	<ref>~~[http://dx.doi.org/10.1088/0741-3335/49/12B/S01~~ F. Wagner, ''A quarter-century of H-mode studies'', Plasma Phys. Control. Fusion '''49''' (2007) B1-B33]</ref>		<ref>F. Wagner, ''A quarter-century of H-mode studies'', [[doi:10.1088/0741-3335/49/12B/S01\|Plasma Phys. Control. Fusion '''49''' (2007) B1-B33]]</ref>

	A variety of mechanisms can give rise to sheared flow, or favour its growth:		A variety of mechanisms can give rise to sheared flow, or favour its growth:
	* The main process for sheared flow generation is generation by the turbulence itself via the [[Reynolds stress]] mechanism. Simply put, transport generated by the fluctuations produces a radial current ''j<sub>r</sub>'' that spins up the plasma via the ''j'' × ''B'' [[:Wikipedia:Lorentz force\|Lorentz force]]. <ref>~~[http://dx.doi.org/10.1063/1.859681~~ P.H. Diamond and Y.-B. Kim, ''Theory of mean poloidal flow generation by turbulence'', Phys. Fluids B '''3''' (1991) 1626]</ref> <ref>~~[http://dx.doi.org/10.1088/0741-3335/43/10/308~~ S.B. Korsholm et al, ''Reynolds stress and shear flow generation'', Plasma Phys. Control. Fusion '''43''' (2001) 1377-1395]</ref>		* The main process for sheared flow generation is generation by the turbulence itself via the [[Reynolds stress]] mechanism. Simply put, transport generated by the fluctuations produces a radial current ''j<sub>r</sub>'' that spins up the plasma via the ''j'' × ''B'' [[:Wikipedia:Lorentz force\|Lorentz force]]. <ref>P.H. Diamond and Y.-B. Kim, ''Theory of mean poloidal flow generation by turbulence'', [[doi:10.1063/1.859681\|Phys. Fluids B '''3''' (1991) 1626]]</ref> <ref>S.B. Korsholm et al, ''Reynolds stress and shear flow generation'', [[doi:10.1088/0741-3335/43/10/308\|Plasma Phys. Control. Fusion '''43''' (2001) 1377-1395]]</ref>
	* This radial current can also actively be produced by electrode biasing. <ref>~~[http://link.aps.org/doi/10.1103/PhysRevLett.63.2365~~ R.J. Taylor et al, ''H-mode behavior induced by cross-field currents in a tokamak'', Phys. Rev. Lett. '''63''' (1989) 2365-2368]</ref>		* This radial current can also actively be produced by electrode biasing. <ref>R.J. Taylor et al, ''H-mode behavior induced by cross-field currents in a tokamak'', [http://link.aps.org/doi/10.1103/PhysRevLett.63.2365 Phys. Rev. Lett. '''63''' (1989) 2365-2368]</ref>
	* Sheared flow may be favoured by reduced viscous damping, which might explain the dependence on rational surfaces observed in the stellarator W7-AS. <ref>~~[http://dx.doi.org/10.1088/0741-3335/42/7/306~~ H. Wobig and J. Kisslinger, ''Viscous damping of rotation in Wendelstein 7-AS'', Plasma Phys. Control. Fusion '''42''' (2000) 823-841]</ref>		* Sheared flow may be favoured by reduced viscous damping, which might explain the dependence on rational surfaces observed in the stellarator W7-AS. <ref>H. Wobig and J. Kisslinger, ''Viscous damping of rotation in Wendelstein 7-AS'', [[doi:10.1088/0741-3335/42/7/306\|Plasma Phys. Control. Fusion '''42''' (2000) 823-841]]</ref>
	* Sheared flow can also be generated by external momentum input.		* Sheared flow can also be generated by external momentum input.

	The details of the feedback mechanism between turbulence and sheared flow are the subject of ongoing studies.		The details of the feedback mechanism between turbulence and sheared flow are the subject of ongoing studies.
	<ref>~~[http://link.aps.org/doi/10.1103/PhysRevLett.72.2565~~ P.H. Diamond et al, ''Self-Regulating Shear Flow Turbulence: A Paradigm for the L to H Transition'', Phys. Rev. Lett. '''72''' (1994) 2565 - 2568]</ref>		<ref>P.H. Diamond et al, ''Self-Regulating Shear Flow Turbulence: A Paradigm for the L to H Transition'', [http://link.aps.org/doi/10.1103/PhysRevLett.72.2565 Phys. Rev. Lett. '''72''' (1994) 2565 - 2568]</ref>
	<ref>~~[http://link.aip.org/link/?PHPAEN/16/012504/1~~ M.A. Malkov and P.H. Diamond, ''Weak hysteresis in a simplified model of the L-H transition'', Phys. Plasmas '''16''' (2009) 012504]</ref>		<ref>M.A. Malkov and P.H. Diamond, ''Weak hysteresis in a simplified model of the L-H transition'', [http://link.aip.org/link/?PHPAEN/16/012504/1 Phys. Plasmas '''16''' (2009) 012504]</ref>

	In summary, the H-mode is the consequence of a self-organizing process in the plasma.		In summary, the H-mode is the consequence of a self-organizing process in the plasma.