Diagnostics Method for 2-D Velocity Distribution Function of Beam Deuterons Using Visible Light of Energetic 3He in Deuterium Plasmas

Abstract

In high-temperature plasmas, fast ion diagnostics is one of the important components for plasma heating. Therefore, it is important for fusion research to confirm and understand the physics of fast ions in experimental devices. Although conventional spectroscopy measurements have excellent energy resolution, it is difficult to measure fast deuterons with MeV order energy. The energy resolutions for neutron and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\gamma $ </tex-math></inline-formula> -ray measurements are low and need to be improved. A diagnostics method using the visible light (VIS) spectrum of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> He produced by the deuteron–deuteron reaction has been proposed. The previous studies did not consider the measurement line-of-sight (LOS) in the actual device. In this article, the observability of the proposed method is evaluated considering the spatial distribution of the temperature and density and the direction of ion motion in the deuterium beam-injected ITER deuterium plasma. It is shown that the change of the Doppler broadening of the VIS spectrum due to the formation of beam deuteron tails (non-Maxwell component) is sufficiently larger than the resolution of the spectrometer, it is strongly dependent on the LOS. The ratios of emissivity to bremsstrahlung are 40%–50% in the vertical LOS and 4%–7% in the tangential LOS.