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Effective plasma radius: Difference between revisions
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* ''r''<sub>eff</sub> = ''dV/dS'' | * ''r''<sub>eff</sub> = ''dV/dS'' | ||
This definition is more general. | This definition is more general. | ||
== Effective radius based on poloidal cross sections == | |||
A poloidal cross section is a cut of the flux surface with the plane ''φ = cst''. | |||
The result of such a cut is a closed curve, of which its circumference and area are easily determined; and effective plasma radius can then be deduced, assuming the curve deviates only slightly from a circle. | |||
The mean plasma radius can be determined by averaging the result over the angle ''φ''. | |||
While the procedure is adequate for toroidally symmetric plasmas, it is not clear that this is also the case for non-axisymmetric systems, since the flux surface intersects the plane ''φ = cst'' obliquely, possibly leading to an over-estimate of the actual plasma size. | |||
The intersection angle can be deduced from the inner product | |||
:<math>\vec \nabla \psi \cdot \vec \nabla \phi</math> | |||
which is zero for axisymmetic systems (since ''ψ'' does not depend on ''φ''), but non-zero for stellarators. | |||
== Effective radius based on field lines == | == Effective radius based on field lines == | ||