Optimal Rate of Injected Heating for the Attainment of Ignition

The plasmas to be produced by Ignitor have been extensively studied and the attainment of ignition has been shown to be possible with ohmic heating alone under realistic conditions for the high density regimes that characterize this experiment. The rate of increase of the plasma density needs to be optimized while both the toroidal 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 poorer than the stechiometric 50/50 deuterium-tritium percentage leads to requiring an externally injected from of heating. A Radio Frequency (RF) system providing Ion Cyclotron Resonance Heating (ICRH) is included in the Ignitor design. Here we present studies performed by considering a simple model for the ICRH power deposition for different timing of the RF heating pulse. The injected power is introduced in the equilibrium-transport code by assigning the region where the heating pulse is deposited and the total power absorbed during a selected time interval. Even by this simplified model it is possible to identify different heating scenarios. 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. Moreover applying auxiliary heating the end of the current ramp, and producing a wider deposition profile can modify the current density profile and offer the possibility to affect of the nature of the sawtooth oscillations that may be excited.