Development of diagnostic beams for alpha particle measurement on LHD and ITER

In this paper, a measurement system applicable to the LHD or ITER project is examined using a high-energy neutral beam in combination with a neutral-particle analyzer. As has been pointed out in the earlier works[1,2], beam energy in the range of that of the alpha particles is preferable. The escaped neutral particles should be detected at a forward angle, in order to make the relative velocity between the donor atom and the alpha particle small enough. It is considered that the relevant charge exchange cross section (1) decreases rapidly when the relative energy is greater than 200 keV. In the present work, only helium and lithium beams are considered, since a heavier particle beam requires a higher acceleration voltage to achieve the same beam velocity. (J.P.N.)