Greenwald limit: Difference between revisions
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The Greenwald limit is an operational limit for the density in magnetic confinement devices: | The Greenwald limit is an operational limit for the density in magnetic confinement devices: | ||
<ref>[ | <ref>[[doi:10.1088/0741-3335/44/8/201|M. Greenwald, ''Density limits in toroidal plasmas'', Plasma Phys. Control. Fusion '''44''' (2002) R27-R53]]</ref> | ||
:<math>n_G = \frac{I_p}{\pi a^2}</math> | :<math>n_G = \frac{I_p}{\pi a^2}</math> | ||
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The mechanism behind this phenomenological limit is not understood, but probably associated with edge gradient limits. | The mechanism behind this phenomenological limit is not understood, but probably associated with edge gradient limits. | ||
Recently, an explanation based on the formation of magnetic island was proposed. <ref>[[doi:10.1103/PhysRevLett.108.165004|D.A. Gates and L. Delgado-Aparicio, ''Origin of Tokamak Density Limit Scalings'', Phys. Rev. Lett. '''108''' (2012) 165004]]</ref> | |||
== References == | == References == | ||
<references /> | <references /> | ||
Revision as of 13:14, 11 July 2012
The Greenwald limit is an operational limit for the density in magnetic confinement devices: [1]
where nG is the density in 1020 m-3, Ip the plasma current in MA, and a the minor radius in m.
In tokamaks (and RFPs), exceeding the Greenwald limit typically leads to a disruption, although sometimes the limit can be crossed without deleterious effects (especially with peaked density profiles). Stellarators can typically exceed the Greenwald limit by factors of 2 to 5, or more (replacing Ip by an equivalent current corresponding to the magnetic field).
The mechanism behind this phenomenological limit is not understood, but probably associated with edge gradient limits. Recently, an explanation based on the formation of magnetic island was proposed. [2]