LAUSR

The effects of hydrogen isotopes (hydrogen and deuterium) were investigated in electron-cyclotron-resonance-heated plasma in the Heliotron J. In order to evaluate particle diffusivity and convection velocity separately, density modulation experiments were performed. Different modulation frequencies (50, 100, and 125 Hz) were applied in order to confirm the results. A smaller diffusion coefficient and a lower inwardly directed convection velocity were obtained at 50 Hz modulation in deuterium-dominant plasma than in hydrogen-dominant plasma, while clear differences were not found at 100 and 125 Hz. The difference in the estimated values is likely to be due to a different spatial response at each frequency. The results suggest that an isotope effect on particle confinement exists in Heliotron J.