The use of D³He plasma in future fusion reactor is one of the promising alternatives. In this plasma, fraction of fusion power carried by neutrons is small and highly efficient fusion is made possible by recovery of the fusion power carried by high-energy protons. The study to use this plasma in Tokamak-based configuration keeping radiation losses lower, is important for improving system efficiency and for increasing social acceptability in future fusion energy systems. We have investigated the burning characteristics of this plasma considering distortion in the fuel-ion velocity distribution functions[1-4]. When the fraction of the number of fuel ions increases owing to the distortion, in the velocity range where the fusion cross section is small, velocity-averaged fusion reactivity decreases. We have estimated the reduction in T(d,n)⁴He reactivity (14MeV neutron generation rate) including the effects of the Nuclear Elastic Scattering[2,3] and magnetic field configuration[4].

In this paper, we attempt reducing the 14MeV neutron generation rate by ICRF injection. So far, many studies to control the fuel-ion distribution function (fusion reactivity) by ICRF heating have been made, however, in most of the previous studies the enhancement in the main fusion reactivity, e.g. ³He(d,p)⁴He (T(d,n)⁴He) reactivity in D³He (DT) plasma, has been considered. In this paper we focus our attention on the side reaction, i.e. T(d,n)⁴He reaction in D³He burning plasmas, and try to reduce the T(d,n)⁴He reactivity by considerably small RF-power input. It is shown that owing to the small RF power (1/100-1/200 of the fusion power) absorption in tritons, the 14-MeV neutron generation rate decreases by about 20-30% from the values for Maxwellian plasmas. An operation mode of D³He fusion system in which 14MeV neutron generation is suppressed, is proposed.

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