Island divertor in a helical-axis heliotron device (Heliotron J)

A new configuration with i/2 pi similar to 0.5 is proposed as an island div ertor configuration ill Heliotron J, a small size l = 1/M = 4 helical-axis heliotron device. In this case, both the m = 8/n = 4 edge islands and the l ast closed flux surface can keep simultaneously the moderate size. As a fir st step of an island divertor design with this configuration, edge field ch aracteristics are numerically investigated assuming a target plate at r(tar get) = 0.33 m (5 cm inside from the chamber wall). It is shown that the div ertor fields cross the target at four discrete regions per a field period. The connection length from the edge to the target plate is in the range of 50-400 m, The total value of the 'wetted area' for the whole torus is about 600 cm(2). The incidence angle of the diverted field lines to the target p late is less than 10 degrees, (C) 2001 Elsevier Science B.V. All rights res erved.