Poloidal shear flow, driven by the radial electric field, decreases the beta limit determined by the ideal interchange mode in a heliotron/torsatron configuration with unfavourable curvature. The reduction factor is estimated as (1-(kvE')2/(k'vpA)2) for localized modes, where k, is the wave number in the poloidal direction, kis the parallel wave number along the magnetic field, vEand vpAare the poloidal shear flow and the poloidal Alfven velocities, respectively, and primes denote the radial derivative. For>LE, the growth rate of the m=1 mode becomes smaller than that for vE= 0; however, the stabilizing effect disappears and the poloidal shear flow enhances the growth rate for展开▼
