Experimental Study of High-Beta Tokamak Stability

The stability properties of high-beta tokamak equilibria with $\epsilon {\beta }_p\gtrsim 1$ and $〈\beta 〉$ in the range of 10% have been studied with use of a dual-beam C${\mathrm{O}}_2$-laser interferometer system. Two equilibria with $〈\beta 〉$ of 9% and 13% were observed to be stable. Another equilibrium with $〈\beta 〉$ of 10% was observed to be unstable with the characteristics of a high-toroidal-modenumber ballooning mode.