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Abstract: The sustainable detachment has been achieved in LHD. The line-averaged electron density of the detachment plasmas is typically over 1.0×1020 m−3. The difference in the broad component of the Hα spectral line profiles between the attachment and detachment plasmas has been observed. In attachment, the divertor flux much affects the neutral hydrogen generation and the large inward flow up to 1.5×104 m/s seemed to be due to the reflection is observed. In detachment, the much smaller flow velocity along the sight lines and the lower Doppler temperature are observed. These observations represent the drastic reduction of the divertor flux and the decrease of the edge electron temperature involved with detachment. [Copyright &y& Elsevier]

Abstract: In the helical-axis heliotron configuration, bumpiness of the confinement field ε b is introduced to control the plasma transport. The plasma performance were experimentally investigated in Heliotron J for three configurations with ε b =0.01, 0.06 and 0.15 at ρ =2/3. The obtained volume-averaged stored energy depends on the configuration. To understand the observed difference in global energy confinement, the ε b-control effects on the edge plasma is discussed. For ε b =0.01, the plasma density and temperature in the peripheral region is low compared to other cases. This poor plasma edge relates to the observed low stored energy or poor energy confinement for ε b =0.01. [Copyright &y& Elsevier]