Steady state tokamak reactor based on the bootstrap current

Abstract

A concept of a steady state tokamak fusion reactor based on the bootstrap current is presented. Operation at high poloidal beta (β_p ≥ 2.0) and high q (4–5) with a relatively small limit on ∈β_p (< 0.5) makes it possible to drive a bootstrap current constituting up to 70% of the total plasma current without exceeding the Troyon beta limit. The rest of the plasma current can be driven by the high energy neutral beam with an energy multiplication factor Q of 30. Energy confinement scaling laws predict that the reactor condition is attainable by increasing the major radius up to 9 m in such a high β_p and high q plasma at a relatively low plasma current (12 MA) with a confinement enhancement factor of 2 compared with the L-mode scaling. This reactor has a reasonable size (V_p = 1500 m³) and fusion output power (2.5 GW) and is consistent with present knowledge regarding tokamak plasma physics, namely the Troyon limit, the energy confinement scalings, the bootstrap current and the current drive efficiency (neutral beam current drive with a total power of 70 MW and a beam energy of 1 MeV) with good prospects for the formation of a cold and dense divertor plasma.