Analysis of Ignitor Discharges with Double X-point Magnetic Configurations

The Ignitor experiment\footnote{B.Coppi, A.Airoldi, F.Bombarda, et al.,\textit{Nucl. Fusion} \textbf{41}, 1253 (2001)} was proposed and designed to achieve ignited and sub-ignited conditions in well confined deuterium-tritium plasmas. Thanks to its unique features (high magnetic field up to 13 T, high plasma current up to 11 MA, and high plasma density up to $5 \times 10^{20} \rm m^{-3}$), Ignitor is the only device capable of exploring plasma regimes that are relevant to a net power producing D-T reactor and are not accessible to other existing or planned machines. Double X-point scenarios with magnetic field up to 13 T and plasma current up to 9 MA are analyzed. In these configurations, the access to a high confinement state is assumed when the available plasma heating power, supported by the injected auxiliary power, is larger than the L-H threshold value, according to recent suggested scalings\footnote{D.C. McDonald, A.J. Meakins, et al., \textit {PPCF} \textbf{48}, A439 (2006)}. The H-regime is modeled by a global reduction of the thermal transport coefficients used for the L-regime. Situations in the presence and in the absence of sawtooth oscillations have been investigated. Quasi-stationary conditions can be attained when a process producing re- distribution of pressure and current profiles is active.