Limits of Possible Operation of the R-Tokamak Due to Ideal Mhd Instabilities

摘要

A series of MHD stability calculations was made with the ERATO code to know the maximum beta which can be expected for the R-Tokamak using the parameters of the second phase design (an aspect ratio of 2.75, ellipticity of 1.8, and triangularity of 0.3). The highest beta obtained under the condition that both the n=1 free boundary mode (with no wall stabilization) and the n=infinity ballooning modes are stable is about 6% at q sub s approximately equal to 2.0 and q sub O at the Mercier limit on axis. This result was found by performing some optimization of the current and pressure profiles. If only the ballooning modes are concerned, the limiting beta becomes 8.6%. The sensitivity of the result to elongation was studied. It was found that the maximum beta increases and then decreases with elongation. The optimum beta is obtained for an elongation of 1.8 if both the n=1 kink and n=infinity ballooning limits are considered and of 2.0 if only ballooning modes are considered. These results are compared with proposed scaling laws.