Role of Fusion Product Measurements in Physics Understanding of a Burning Plasma

The roles of fusion products in diagnosing plasmas are quite diversified and rich in scientific content. From the early days to the new frontier of burning plasmas, the study of fusion products has allowed a deeper understanding of the physics found in these plasmas, spanning all configurations, in both magnetic and inertial confinement. In many early experiments, the measurement of plasma performance was based almost entirely on neutron yield measurements. Since then, the capability to measure fusion products has grown tremendously, and many new measuring techniques have been successfully tested and used in experiments. The first role is based on single-particle diagnosis, which can yield important information on performance, confinement, source and current profiles, plasma fluctuations, effects of ripples, MHD mode structure, etc. The second role, which has expanded tremendously in the last few years, includes the diagnosis of collective effects, which can yield additional information on instabilities, heating, and many others. This scientific capability is enhanced by the large number of fusion products (neutrons, charged particles, gammas) generated by the primary or secondary fusion processes such as the commonly studied, D+D, D+T and D+3He reactions. This paper will review the applications of fusion product measurements used in the scientific study of plasma confinement and stability, and will describe the prospects and opportunities offered in burning plasma experiments such as ITER