STEADY-STATE PROFILES IN HIGH BOOTSTRAP FRACTION TOKAMAK DISCHARGES WITH REVERSED SHEAR

Tokamaks often show improved core confinement when the magnetic shear in the central region is reversed. Furthermore tokamaks operating in a mode in which the current is mostly sustained by bootstrap current te nd to naturally form reversed shear profiles. For a fixed heating prof ile the improved core confinement will cause the pressure profile to p eak which effects the equilibrium through the bootstrap current term. We show that equilibria do not necessarily exist for tokamaks that hav e a high bootstrap current fraction and enhanced confinement in the re versed shear region.