Ignitor is based on a axisymmetric configuration with an elongated cross section and a tight aspect ratio. In particular, two kinds of equilibrium plasma configurations for the most advanced operations have been investigated:
a configuration (Ip≤11 MA) where the first wall, which is covered with molybdenum tiles, acts as an extended toroidal limiter (see section Density and impurities) and the resulting peak power loads do not exceed 1.8 MW/m 2 ;
- an X-point configuration, in addition to the standard limiter one, but at lower currents and smaller cross-sections, which is produced by the poloidal field system. For example, configurations with double X-points just outside the first wall at 10 MA and at the edge safety factor q~3 can be produced by reinforcing some of the existing poloidal field coils . The X-point configuration has been included in the Ignitor design in order to produce, with the appropriate level of plasma heating, the H-regime. In this case a sufficiently long confinement time for ignition is predicted on the basis of existing scalings but the possibility that impurities may not be sufficiently concentrated at the edge remains a concern .
Furthermore, three different operations scenarios that differ by the maximum value of the current and of the toroidal magnetic field are envisaged: 11 MA/13 T, 7 MA/9 T, 6 MA/9 T.
1) B. Coppi et al, Nucl. Fusion 41, 1253 (2001)
2) B. Coppi et al, Overview Paper OV/P-02, Proceedings of the 24 th IAEA Fusion Energy Conference, San Diego, US, 8-13/10/2012