Study of fusion reaction products emitted from deuterium plasmas provides information on the confinement and slowing down of fast charged particles. The information gained through these studies has a bearing on the confinement of a-particles and may contribute to predictions concerning the a-particle heating in deutrium-tritium plasmas. Proton spectra have recently been measured at JET from the reaction d + 3He Æ p + a at energies around Ep = 14.6MeV. 3He was introduced by gas puff (for ICRF minority heating) but is otherwise always present as a product of the reaction d + d + 3He + n. The instrument and some of the results obtained are described. Neutrons of about 14.0MeV from the reaction t' + d Æ a + n (where the 1.0MeV tritons t' come from d + d Æ p + t') can be studied given a spectrometer of high efficiency (e 0.2cm2) and low sensitivity to 2.5MeV neutrons. A proposed spectrometer design and its envisaged diagnostic capabil ties are discussed. Besides studying the fast ions in the plasma through their fusion burn up products, atomic "burn up" is suggested as another possibility; i.e. the radiative recombination e + t + g + to of fast tritons and measurement of their velocity distribution as represented in the neutral to emission. A comparison is made of limitations and capabilities between charged particle, neutron and neutral to measurements for purpose of studying the fast ion physics and of diagnosing the plasma.