A first attempt to observe a nuclear-elastic-scattering (NES) effect caused by energetic protons on deuteron slowing-down behaviour was made on the Large Helical Device located at the National Institute for Fusion Science. The NES effect on fast-ion slowing-down property can have influence on fast-ion confinement property, ion heating, fusion reaction rate coefficient, etc. An intense hydrogen beam was injected into a deuterium plasma to create a knock-on tail, i.e., a non-Maxwellian energetic component in the deuteron velocity distribution function. We conducted two types of experiment, i.e.,(1) observation of the knock-on tail slowing-down property and (2) observation of the NES effect on fast-ion slowing down time. The phenomena are discussed in terms of the difference in the decay process of the D(d,n) 3 He neutron generation rate after neutral beam heating is terminated between the cases when the knock-on effect is influential and not influential, and also from the difference in the neutron decay times. The results of a series of experiments indicate that the NES effect caused by energetic protons can have an impact on fast-deuterons slowing-down process.

A knock-on tail formation in deuteron velocity distribution function due to nuclear elastic scattering (NES) by energetic protons and its observation method using γ-ray-generating 6 Li(d,pγ) 7 Li reaction are examined for proton-beam-injected deuterium plasmas. The proton velocity distribution function is obtained by means of the ion trajectory analysis in a Tokamak magnetic configuration. The knock-on tail in two-dimensional (2D) deuteron velocity distribution function due to NES by energetic protons is evaluated via Boltzmann collision integral and 2D Fokker-Planck simulation. From the 2D deuteron velocity distribution function obtained, enhancement of the emission rate of 0.48-MeV γ-rays by 6 Li(d,p) 7 Li*, 7 Li*→ 7 Li+γ reaction due to NES is evaluated. It is shown that the γ-ray emission rate is significantly influenced by the magnitude of the knock-on tail, and the γ-ray-generating reaction can be a useful tool for the knock-on tail observation.

Line identification of boron and nitrogen emissions in EUV andVUV wavelength ranges in the impurity powder dropping experiments of LHD and its application to spectroscopic diagnostics