Ignition and Burning Plasma Regimes in the Double Null Configuration of Ignitor$^*$

A new operating scenario for Ignitor with {$B_{T} \approx 13$ T, $I_{p} \approx 9$ MA} and a double X-point configuration (X- points just outside the first wall) has been investigated. The analyses carried out are directed to optimizing the plasma volume, the magnetic configuration and the relevant ``safety factor'' near the first wall. A transport analysis has been performed to simulate the current density evolution (important for the considered sequences of equilibrium configurations) and to verify the possibility of accessing H-regimes. The H-regime power threshold has been estimated from recent scalings based on a variety of experiments. This threshold power is consistent with that available from the provided ICRH system, combined with the Ohmic and $\alpha$-particle heating. In the numerical simulations a volume average density {$\langle n_{e} \rangle\approx 3\times 10^{20} \rm m^{-3}$}, an average {$Z_ {eff} \approx 1.5$}, and 3 MW of ICRH a power absorbed by the plasma have been considered. Ignition and advanced parameters as those expected for the ``standard'' 11 MA scenario with the ``extended'' first wall configuration of Ignitor can be reached. Even without accessing the H-regime and with pessimistic assumptions about the energy confinement time, plasma conditions of relevance to the physics of burning plasmas can be attained.\\$^*$Sponsored in part by ENEA and CNR of Italy and by the US D.O.E.\\