Retention in tungsten resulting from extremely high fluence plasma exposure

PISCES-B was used for a series of high-fluence plasma exposures to investigate the deuterium fuel retention properties of tungsten, when exposed to continuous plasma irradiation. The goal was to determine whether the fuel retention in the tungsten saturates at sufficiently high fluence, or continues to increase as a function of the plasma fluence. During pure deuterium plasma exposure, up to a maximum deuterium fluence of 2 × 1028 m−2, retention results indicate that saturation is not reached and that retention scales as the square root of time, indicative of diffusion dominating the fuel uptake of the tungsten. However, measurements performed while sculpting the PISCES plasma to replicate a burning plasma, by adding a small amount (5%) of helium ions to the incident deuterium plasma, indicate the deuterium uptake in the target is severely inhibited.