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The measured D-D neutron rate of neutral beam heated JET baseline and hybrid H-modes in deuterium is found to be between approximately 50% and 100% of the neutron rate expected from the TRANSP code, depending on the plasma parameters. A number of candidate explanations for the shortfall, such as fuel dilution, errors in beam penetration and effectively available beam power have been excluded. As the neutron rate in JET is dominated by beam-plasma interactions, the 'neutron deficit' may be caused by a yet unidentified form of fast particle redistribution. Modelling, which assumes fast particle transport to be responsible for the deficit, indicates that such redistribution would have to happen at time scales faster than both the slowing down time and the energy confinement time. Sawteeth and edge localised modes are found to make no significant contribution to the deficit. There is also no obvious correlation with magnetohydrodynamic activity measured using magnetic probes at the tokamak vessel walls. Modelling of fast particle orbits in the 3D fields of neoclassical tearing modes shows that realistically sized islands can only contribute a few percent to the deficit. In view of these results it appears unlikely that the neutron deficit results from a single physical process in the plasma.

In magnetic fusion experiments, the cross sections for the D-T and D- ^3 He fusion reactions are increased by as much as 50% if the fuel remains spin polarized parallel to the magnetic field. The goal of this study is to assess the feasibility of lifetime measurements of spin polarization, in magnetic fusion relevant conditions, on the DIII-D tokamak using relative changes in charged fusion product (CFP) loss measurements that depend upon the differential fusion cross section d σ /dΩ. Relative measurements that capture changes in the escaping CFP pitch, poloidal, and energy distributions are studied in two realistic TRANSP calculated plasma scenarios: (a) vector-polarized ^3 He and D pellets are injected into a hot hydrogen plasma to produce thermonuclear reactions, and (b) a tensor-polarized deuterium pellet is injected into an L-mode hydrogen background plasma that includes unpolarized ^3 He neutral beam injection. Ideal CFP signals in both scenarios show substantial pitch sensitivity to polarization for 14.7 MeV proton detection at a poloidal angle of $-56^{\circ}$ (on the outer wall in the ion $\nabla B$ direction), and strong sensitivity to polarization for 3.6 MeV alpha flux detection by an array of poloidal detectors. Energy-resolved measurements of 14.7 MeV protons are also sensitive to the degree of polarization for the $-56^{\circ}$ port in the beam-plasma scenario. A realistic assessment of CFP signals in the thermonuclear scenario show count rates in the range of $2\times10^4$ cps for pitch-resolved proton detection and $2\times10^5$ cps for alpha flux measurements. Reduced chi-squared $\chi^{\,2}_\mathrm r$ calculations show polarization lifetime measurements are feasible for either proton or alpha detection of both enhanced or suppressed polarization for the thermonuclear scenario. Measurements of gamma rays produced in the weak $\textrm{D} + {}^{3}\textrm{He} \rightarrow \gamma+ {}^5\textrm{Li}$ branch complement the CFP measurements.

Recent Experimental Advanced Superconductivity Tokamak experiments have been dedicated to the studies of increasing ion temperature using Neutral Beam Injection (NBI) in synergy with radio-frequency waves in the Ion Cyclotron Range of Frequencies (ICRFs) in third harmonic. They showed that this scenario effectively accelerates fast deuterium ions and produces a larger tail of fast neutrons with E > 3.0 MeV, as measured by Neutron Energy Spectrum. Comparing to the scenario with 2.2 MW NBI alone, adding an addition of 0.3 MW ICRF power leads to an enhancement of fusion yield by 67% (from ${\text{0}}{{.73 \times 1}}{{\text{0}}^{{\text{14}}}}{\text{ n}}\;{{\text{s}}^{ - {\text{1}}}}$ to ${\text{1}}{{.22 \times 1}}{{\text{0}}^{{\text{14}}}}{\text{ n}}\;{{\text{s}}^{ - 1}}$ ) and an increase of core ion temperature by $\Delta {T_{\text{i}}}\sim 7{\text{80 eV}}$ . Besides, the simulation results of TRANSP show that the neutron yield produced by 0.2 MW ICRF in third harmonic with NBI synergy is roughly consistent with the experimental results. Meanwhile, the 80 keV fast ion tail generated by NBI can be heated up to 400 keV and 600 keV by the 0.2 MW and 1.0 MW ICRF with the synergistic effect, respectively. In addition, it is observed for the first time that this ICRF-NBI synergy leads to the excitation of fishbone instabilities with characteristic frequencies of (10–20) kHz. Furthermore, parameter scans of ICRF/NBI power and plasma density were performed for third harmonic ICRF and NBI synergetic heating schemes. It is found that the neutron yield increases nonlinearly as the ICRF power or plasma density increases.