Current profiles and major disruptions in a lower-hybrid current drive tokamak

Summary - The radial rf current profile of the lower-hybrid current drive tokamak is estimated using an rf power damping model for various Gaussian type nz spectra (=exp(-(nz-nzc)2/hz)), and condition for stability against major disruptions are examined using the criterion of the tearing mode instability. The value of nzc determines the spatial damping of the rf power and the resultant rf current profile. The value of hz determines the extent of the damping of the rf power and the resultant absolute value of the rf current. The peaking and flattening characteristics of current profile which is free from disruption are obtained when the rf power is not damped at the boundary region and when the extent of damping is relatively small even if the rf power begins to damp at regions close to boundaries, where the rf spectrum has relatively large phase velocity and is not so broad. (author)