Control of neoclassical tearing modes in large tokamaks

Some self-consistent effects pertaining to feedback control of neoclassical tearing modes in high temperature large tokamaks are investigated. For the ECRH scheme of local electron heating, it is shown that the self consisten t bootstrap currents created by the driven pressure gradients within the is land are comparable to those due to the usually considered resistivity chan ge mechanism. Similar self-consistent currents can also arise from pressure gradients created by density and energy deposition from neutral beams, the reby offering a new possibility for neoclassical mode control. The stabiliz ing current in such an application of neutral beams is estimated. It is fur ther shown that such a feedback scheme can be made even more effective thro ugh appropriate modulation of the beam source to match the phase variation arising from the island rotation.