We demonstrate 2D reconstructions of the fast-ion velocity distribution from two-view fast-ion D-alpha (FIDA) measurements at the EAST tokamak. By expressing the distribution in a basis relying on the fast-ion slowing-down process in fusion plasmas, the smoothness and velocity-space resolution of reconstructions are improved. We reconstruct distributions of fast ions born from simultaneous co- and counter-current neutral beam injection and detect the expected distinct change in fast-ion birth pitch when comparing discharges utilizing different neutral beam injectors. For purely co-current injection, we find a good agreement between TRANSP-predicted and reconstructed fast-ion densities, pressures and current densities for energies above 20 keV. We furthermore illustrate the improvement of the reconstructed high-energy range (> 40 keV) of the distribution by combining FIDA with neutron emission spectroscopy measurements with the compact single-plate EJ301 scintillator.

Ion Cyclotron Range of Frequencies (ICRF) heating and Neutral Beam Injection (NBI) can have synergy due to the acceleration of NBI beam ions by ICRF wave fields at their harmonics. To understand the influence of ICRF-NBI synergy on fast ion distribution and plasma performance, dedicated experiments and TRANSP simulations have been carried out on EAST. The simulation results are consistent with the experimental results. They show that the ICRF-NBI synergy not only accelerates the NBI beam ions with energy lower than 80 keV to energy larger than 300 keV, but also generates fusion neutrons with energy larger than 3 MeV. Moreover, ICRF-NBI synergy improves the plasma performance by increasing the poloidal beta, plasma stored energy, core ion temperature, total neutron yield and kinetic pressure. In a typical H-mode plasma with 1.0 MW NBI and 1.5 MW ICRF power, it was observed that ICRF-NBI synergy increases the poloidal beta, plasma stored energy, core ion temperature and neutron yield by ∼35%, 33%, 22% and 80%, respectively. Various parameter scans show that the ICRF-NBI synergetic effects can be enhanced by decreasing the minority ion concentration or the distance between the harmonic resonance and magnetic axis, or by increasing the ICRF heating power or NBI beam energy. Consequently, this leads to a generation of fast ions with higher energy. For instance, the maximum energy of the fast ion tail increases from 300 to 600 keV as n(H) decreases from 5% to 0.1%.

Neutron emission spectroscopy (NES) measurement aimed at providing the information on fast ions induced by auxiliary heating systems at Experimental Advanced Superconducting Tokamak (EAST), with a liquid scintillation detector is described. It is the first time that the NES diagnostics are employed to probe fast ions induced by neutral beam injection (NBI) at EAST. The time trace of the fusion neutrons, obtained by the liquid scintillation detector, was consistent with the result measured by a standard ²³⁵ U fission chamber under NBI heating scenario, which verifies the performance of the detector. NUBEAM code is used to determine the fast deuteron velocity distribution using the parametrized plasma profiles as input. The pulse height spectrum of the fusion neutrons was successfully reproduced by combining the simulation of the neutron energy spectrum and the calculation of the detector response functions. The experimental data are also interpreted from a view of weight functions, which illustrate the velocity-space sensitivity of the liquid scintillation detector with a radial line of sight. The results demonstrate the capability of the liquid scintillation detector to contribute to studies on fast-ion physics at EAST.