Observation of m ≥ 2 modes in plasmas with 1/2 ≤ qa < 1

Internal modes with m=1 and m ≥ 2, which localize around a pitch minimum, have been studied for ultra-low-q plasmas with 1/2 ≤ qa < 1 in REPUTE-1, where m is the poloidal mode number and qa is the safety factor at the plasma surface. One-dimensional stability analysis has shown that, for finite beta, m ≥ 2 modes have a relatively large growth rate compared with those of the m=1 modes. The internal structure of the magnetic fluctuations with m=1 and m ≥ 2 is found to be consistent with the numerically calculated eigenfunctions. (author). 7 refs, 9 figs