Fast-ion measurements with neutron and gamma-ray spectroscopy in thermonuclear plasmas: recent results and future prospects

A high-performance thermonuclear plasma is a strong source of nuclear radiation, which includes neutron emission from the main fusion reactions and gamma-rays born from the interaction of supra-thermal ions and plasma impurities. Spectroscopic measurements of both types of radiation are an indirect probe of the distribution function of the fast ions leading to nuclear emission. In this paper we present a selection of recent results obtained with neutron and gamma-ray spectroscopy as a means to study the energy distribution of supra-thermal particles in high-performance thermonuclear plasmas. We focus in particular on the advancements made possible by the combination of dedicated instrumentation and detailed models based on the nuclear physics behind the emission. Future developments are finally addressed, especially regarding the availability of compact detectors with spectroscopy capabilities, which open up to a full tomographic reconstruction of the fast-ion velocity space.