Irregularities in helium release rates from metal ditritides

Helium release rates from erbium and zirconium ditritide films were measured with 3-s time resolution. All films exhibited some variability in 3He release rates on this time scale, but the nonuniformity of the release rate was greatest for samples undergoing the transition into accelerated release, which occurs when the occluders approach the maximum quantities of helium that they can retain. The 3He release rate variability appeared to be associated with the spontaneous release of helium in bursts of about 109 atoms. The release of bursts of helium was also stimulated by vibrating or flexing the film substrates. Although these effects are not expected based on the diffusion of isolated helium atoms of the lattice, the effects of temperature on helium release rates were consistent with the diffusion model. These observations lead to the conclusion that two distinct mechanisms are responsible for the release of helium from the metal ditritide films