Magnetic shear: Difference between revisions

Magnetic shear (view source)

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 Thus, in 3 dimensions, the shear is a 3 x 3 tensor.
-== Rotational transform ==
-In the context of magnetic confinement, and assuming the existence of toroidally nested magnetic [[Flux surface|flux surfaces]], the only relevant variation of the direction of the magnetic field is the radial gradient of the '''rotational transform''' (field line pitch). The latter is defined as
-:<math>\frac{\iota}{2 \pi} = \frac{d \psi}{d \phi}</math>
-where ''&psi;'' is the poloidal magnetic flux, and ''&phi;'' the toroidal magnetic flux.
-Thus, ''&iota;/2&pi;'' is the mean number of toroidal transits (''n'') divided by the
-mean number of poloidal transits (''m'') of a field line on a flux surface.
-In tokamak research, the quantity ''q = 2&pi;/&iota;'' is preferred (called the "safety factor").
 == Global magnetic shear ==
+In the context of magnetic confinement, and assuming the existence of toroidally nested magnetic [[Flux surface|flux surfaces]], the only relevant variation of the direction of the magnetic field is the radial gradient of the [[Rotational transform|rotational transform]].
 The global magnetic shear is defined as
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 == See also ==
+* [[Rotational transform]]
 * [[Connection length]]
 == References ==
 <references />