The neoclassical bootstrap current effect is investigated in the JT-60 tokamak. The experimental resistive loop voltages are compared with the calculations, using the neoclassical resistivity, with and without the bootstrap current, and the Spitzer resistivity for a wide range of plasma current (Ip = 0.5-2 MA) and poloidal beta (βp = 0.1-3.2). The neoclassical bootstrap current is calculated directly with the force balance equations for viscous and friction forces according to the Hirshman–Sigmar theory. The bootstrap current driven by the fast ion component is also included. The calculated resistive loop voltage is consistent with the neoclassical prediction including the bootstrap current. It is shown that up to 80% of total plasma current is driven by the bootstrap current in the regime with an extremely high poloidal beta value (βp = 3.2) while the beam driven current is negligibly small.
Experimental evidence for the bootstrap current in a tokamak