Momentum transport and plasma rotation profile in toroidal direction in JT-60U L-mode plasmas

Abstract

The characteristics of momentum transport and plasma rotation in the toroidal direction are studied, using near-perpendicular neutral beam injection (PERP-NBI), co tangential and counter (CTR) tangential NBI in JT-60U. Diffusive and non-diffusive terms of momentum transport are evaluated from the transient analysis by using the momentum source modulation. Fast ion losses due to the toroidal field ripple, which locally induces the edge CTR rotation, are used as a novel momentum source. Parameter dependence of these transport coefficients i.e. the toroidal momentum diffusivity (χϕ) and the convection velocity (Vconv), and the relation between momentum and heat diffusivities (χi) are investigated in L-mode plasmas systematically. The toroidal momentum diffusivity increases with increasing heating power and decreases with increasing plasma current. The relation of χϕ and χi to some non-dimensional parameters is investigated. A clear dependence of χϕ/χi on normalized plasma pressure (βN) is observed. It is also found that toroidal rotation velocity profiles in the case with and without external torque input can be almost reproduced by χϕ and Vconv estimated from the transient momentum transport analysis at low β (βN < 0.4).