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Modification of Neutron Emission Spectra and Determination of Fuel Ion Ratio in Beam-Injected Deuterium–Tritium Plasma

Yasuko KAWAMOTO and Hideaki MATSUURA

Applied Quantum Physics and Nuclear Engineering, Kyushu University, 744 Motooka, Fukuoka 819-0395, Japan

(Received 1 December 2015 / Accepted 1 February 2016 / Published 30 June 2016)

Abstract

To stably control and operate a deuterium–tritium (DT) fusion reactor, it is important to accurately obtain the fuel ion ratio n_t/n_d (n is the number density). Previously, fuel ion ratio diagnostic methods using deuterium–deuterium (DD) and DT neutron emission rates have been studied. The reaction rate coefficients and neutron emission spectra, i.e., the shape and peak value, are strongly influenced by external plasma heating such as neutron beam injection (NBI) heating. In this paper, we consider the fuel ion ratio diagnostics by directly measuring the neutron emission spectra, including both beam–thermal and beam–beam fusion reactions, in deuterium beam-injected DT plasma. We also evaluate the slowing-down neutron component, i.e., noise, to examine whether the above method can be used for plasma diagnostics. On the basis of Boltzmann–Fokker–Planck and Monte Carlo neutron transport analyses, the applicability of the method to the beam-injected DT plasma is discussed. It is shown that the feasible plasma parameter regions of measuring for fuel ion ratio diagnostics is increased by beam injection and by adopting neutron detector channels shifted to the high-energy side.

Copyright (c) 2016 The Japan Society of Plasma Science and Nuclear Fusion Research

Keywords

fuel ion ratio diagnostics, fusion blanket, neutron spectrometry, NBI, neutron transport simulation

DOI: 10.1585/pfr.11.2405078

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