The control of vertical instability is studied for DN divertor plasmas
in a tokamak with both passive and active control coils. The characte
ristic parameter of the vertical instability and a second damp stable
operating region of the feedback gain are found. The favorable effects
of higher triangularity and hollow profile on the critical elongation
are demonstrated. (C) 1998 Elsevier Science S.A. All rights reserved.