Effect of convective transport in edge and scrape-off-layer plasmas of ADITYA-U tokamak.

Abstract

The 2-D edge plasma fluid transport code, UEDGE has been used to simulate the edge and scrape-off layer regions of circular limiter plasmas of ADITYA-U. The computational mesh defining the limiter geometry of ADITYA-U has been introduced in the UEDGE code through an in-house developed routine. It has successfully been integrated with the UEDGE code and the measured radial profile of electron density ([Formula: see text]) in the edge region is modelled using the simulations. The plasma discharge for the present study has plasma current [Formula: see text] ∼ 130 kA, duration ∼ 150 ms, chord-averaged electron density ∼ 1.3 × [Formula: see text] [Formula: see text], and central electron temperature ∼ 270 eV has been observed. The maximum toroidal magnetic field is ∼ 1.2 T. It has been found that an inward convective velocity, [Formula: see text] ∼ 1.5 m/s is required in addition to the constant perpendicular diffusion coefficient, [Formula: see text] ∼ 0.2 [Formula: see text]/s to adequately match the measured [Formula: see text] profile in typical discharges of ADITYA-U. The value of [Formula: see text] ∼ 0.2 [Formula: see text]/s is found to lie between the estimated neoclassical diffusivity and Bohm diffusivity.