Pressure driven magnetohydrodynamics instabilities in peaked pressure profile reversed magnetic shear plasmas

For a reversed magnetic shear plasma formed by early neutral beam injection into the HL-2A tokamak, magnetohydrodynamics instability analysis against ideal low-n modes and resistive interchange modes is carried out. Low-n modes located in the low shear region around the shear reversal point are driven unstable by a large pressure gradient, and they are of the characteristics of infernal modes. High pressure in the central negative shear region drives resistive interchange modes with the unstable window extending to r/a ≅ 0.2, but not covering the low shear region around the shear reversal point