Energetic ion diagnostics using neutron flux measurements during pellet injection

Abstract

Neutron measurements during injection of deuterium pellets into deuterium plasmas on the tokamak fusion test reactor (TFTR) indicate that the fractional increase in neutron emission about 0.5 ms after pellet injection is proportional to the fraction of beam-plasma reactions to total fusion reactions in the unperturbed plasma. These observations suggest three diagnostic applications of neutron measurements during pellet injection: (1) measurement of the beam-plasma reaction rate in deuterium plasmas for use in determining the fusion Q in an equivalent deuterium-tritium plasma, (2) measurement of the radial profile of energetic beam ions by varying the pellet size and velocity, and (3) measurement of the "temperature" of ions accelerated during wave heating.