Optimal Rate of Injected Heating to Reach Ignition

The attainment of ignition with ohmic heating alone under realistic conditions for the high density regimes that characterize the Ignitor experiment involves the optimisation of the rate of increase of the plasma density while both the toroidaI field and the plasma current are ramped up. A departure from the optimal conditions such as the presence of an impurity content producing a (Zeff) value greater than 1.5, or a fuel composition different from 50/50 deuterium-tritium leads to requiring the assistance of the Ion Cyclotron Resonance Heating (ICRH) system included in the Ignitor design. The adopted injected power model assigns the region where the heating pulse is deposited and the total power absorbed during a selected interval. A more centrally localized deposition profile assures the major boost to accelerate the attainment of ignition, in the case when the heating power is injected during the current ramp. Applying auxiliary heating at the end of the current ramp, and producing a wider deposition profile can modify the current density profile and affect of the nature of the sawtooth oscillations that may be excited.