Stability Study of High-βFlux-Conserving Equilibria

Abstract

The flux-conserving tokamak model suggested that rapid heating would yield equilibria with high relative energy density {(3 = 2p/B 2 ) while nonetheless allowing control over q> the so-called safety factor for instability within the ideal magnetohydrodynamic plasma model. In this study, we show that this is adequate to provide stability to /3 values of 10%, if there is a superconducting metal shell in the vicinity of the plasma.

Ideal magnetohydrodynamic theory of magnetic fusion systems

“…(5.171), a number of numerical codes have been developed for testing ballooning mode stability (Dobrott et al , 1979;Miller and Moore, 1979;Charlton et al , 1979;Todd et al , 1979;Bernard et al , 1980). Such studies show that by optimizing profiles and cross sections, one can obtain critical (P)'s on the order of 5 -10%.…”

“…, Charlton et al , 1979;Todd et al , 1979), studies have shown that the (p) limits for arbitrary internal modes are most stringent for the n~ao ballooning modes. However, modes with such a fine-scale structure are likely to be affected by other physics (e.g.…”

“…Since these are low-m modes with gross radial structure, many of the stability results have been obtained from numerical computations Schneider and Bateman, 1974;Todd et al , 1977Todd et al , , 1979Berger et al , 1977;Charlton et al , 1979;and Bernard et al , 1980). There is, however, one simple equilibrium model which gives unexpectedly reliable information about the (p) limits.…”

“…[See, for instance, Todd et al (1979), Charlton et al (1979, and Bernard et al 1980). ] These calculations are based on an exact formulation of the Energy Principle in which no expansions are made with respect to (P) or the inverse aspect ratio.…”

Ideal MHD stability properties of pressure-driven modes in low shear tokamaks

“…However, in practice, mode resolution and hence computer memory requirements restrict the analysis to n ( 10. The ballooning theory has been modified to include finite-n corrections, and has been shown to agree with the detailed MHD approach down to n -5 [16][17][18]. Ballooning theory predicts that the largest n modes are the most unstable, and that as n is decreased the growth rate decreases monotonically.…”