A NEW INSIGHT FOR THE QUASILINEAR DIFFUSION COEFFICIENT FOR THE LOWER HYBRID CURRENT DRIVE

The spectral gap problem arises when one tries to explain the experimental problem using the standard self-consistent and non self-consistent quasilinear theory for the driven noninductive radio frequency current. We have revised the well known lower hybrid current drive (LHCD) spectral gap problem, calculating the quasilinear diffusion coefficient using a resonance function (smooth resonance border) rather than the Dirac’s Delta Function (sharp resonance border). A proper calculation of the quasilinear diffusion coefficient, taking the complete form as given by Swanson (1989), has produced a good size wing for the diffusion coefficient in the lower side of the wave spectrum. This wing produces a considerable difference on the value of the driven current approaching the experimentally measured values. Our calculation may be one of possible ways of solving the spectral gap problem for lower hybrid current drive which has been under consideration since last decade. This problem is not yet solved completely (Ide e