Abstract
The fast deuteron (non-Maxwellian component) diagnostic method, which is based on the higher resolution optical spectroscopic measurement, has been developed as a powerful tool. Owing to a decrease in the D-H charge-exchange cross section, the diagnostic ability of conventional optical diagnostic methods should be improved for ∼MeV energy deuterons. Because the 3He-H charge-exchange cross section is much larger than that of D-H in the ∼MeV energy range, the visible light (VIS) spectrum of 3He produced by the dueteron-dueteron (DD) reaction may be a useful tool. Although the density of 3He is small because it is produced via the DD reaction, improvement of the emissivity of the VIS spectrum of 3He can be expected by using a high-energy beam. We evaluate the VIS spectrum of 3He for the cases when a fast deuteron tail is formed and not formed in the ITER-like beam injected deuterium plasma. Even when the beam energy is in the MeV energy range, a large change appears in the half width at half maximum of the VIS spectrum. The emissivity of the VIS spectrum of 3He and the emissivity of bremsstrahlung are compared, and the measurable VIS spectrum is obtained. It is shown that the VIS spectrum of 3He is a useful tool for the MeV beam deuteron tail diagnostics.
Highlights
In a nuclear burning plasma, fast ions are always generated by fusion reactions, neutral beam injection (NBI), radiofrequency heating, and large-angle scattering [1,2,3,4]
The emissivity of the visible light (VIS) spectrum is approximately 1% compared to the emissivity of bremsstrahlung
This paper shows a possibility of Doppler broadening of the VIS spectra of energetic 3He produced by the DD reaction to diagnose the deuteron beam tail in the deuteron velocity distribution function
Summary
In a nuclear burning plasma, fast ions are always generated by fusion reactions, neutral beam injection (NBI), radiofrequency heating, and large-angle scattering [1,2,3,4]. If the instability is driven, the confinement of fast ions deteriorates [7, 8], and the efficiency of plasma heating by fast ions decreases. The elucidation of physics related to fast ions and MHD instabilities is one of the most important subjects in nuclear fusion research. These phenomena can be understood through the velocity distribution function of fast ion (fast ion tail). It is important to diagnose fast ion tails in experimental devices
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