Study of MHD stability β limit in LHD by hierarchy integrated simulation code

Based on LHD experimental result of MHD stability analysis instead of 'conventional' criteria based on ideal linear theoretical prediction, so-called 'MHD stability β limit' for helical plasmas is studied by using a hierarchy integrated simulation. The calculations for the LHD configuration, in which the volume averaged β value of 5% is achieved experimentally, shows that the interchange modes limit the pressure gradient only in the periphery region not in the core region. The achievable β value based on the experimental results through the Mercier parameter is not limited by MHD instabilities and it is considered to increase up to the equilibrium β limit. (author)