Beta limits for ETF

Abstract

ETF (Engineering Test Facility) one-dimensional transport simulations indicate that a volume-average beta of 4% is required for ignition. It is therefore important that theoretical beta limits, determined by requiring equilibria to be stable to all ideal modes, exceed 4%. This paper documents an ideal MHD analysis wherein it is shown that, with appropriate plasma cross-sectional shape and current profile optimization, operation near 5% is possible. The critical beta value, however, depends on the functional form used for ff′, which suggests that higher critical betas could be achieved by directly optimizing the safety factor profile.

Stability analysis for the Big Dee upgrade of the Doublet III tokamak

“…Ideal magnetohydrodynamic (MHD) instabilities are of great concern because they have the potential to limit beta to values below 5%. Therefore, extensive studies have been performed to determine ideal MHD beta limits and the corresponding optimized configurations for various devices [2][3][4][5][6]. Since the maximum value of beta stable to Mercier and ballooning modes, referred to as the critical value and which we denote |3 C , increases with inverse aspect ratio e, elongation K, and triangularity 5, the Big Dee tokamak (e = 2.48, K = 2.15, 5 = 0.45 at the vacuum wall; see Fig.…”

Beta limits for the BIG DEE

“…Using D-D reactions, tokamak reactors become economically attractive when beta, the ratio of volumeaveraged plasma to magnetic pressure, exceeds 5%. Ideal-MHD instabilities are of great concern because they have the potential to limit beta to lower values and so extensive studies have been done in order to determine ideal-MHD beta limits for various configurations [1][2][3][4][5]. Since the maximum stable value of beta, to be denoted /3 C , increases with inverse aspect ratio e, elongation K and triangularity 5, the BIG DEE tokamak [6] (e = 0.40, K = 2.15, 6 = 0.45; see Fig.…”