Volt-second analysis and consumption in Doublet III plasmas

Abstract

A Poynting's Theorem method is used for evaluating the volt-second consumption in a tokamak discharge. The method accurately identifies the inductive and resistive components of the volt-second consumption, and allows both quantities to be determined from magnetic measurements made outside the plasma. Only simple computational techniques are required. Application of the method to typical Doublet III near-circular plasmas (R = 1.43 m, a = 0.44 m, b/a ≅ 1.2) indicates that the flux at the plasma surface required to establish the current flat-top is 2.0 ± 0.2 V·s/MA. Approximately 40% of this flux is consumed in resistive dissipation. This division between resistive and inductive flux differs significantly from that obtained using an alternative data analysis method in which the resistive loss is evaluated at the plasma axis. The reasons for the difference are discussed.