  The particle flux through a two micron diameter orifice into vacuum from a
source chamber filled with solid He exhibits a striking periodic behavior
similar to that of a geyser. This phenomenon is attributed to a periodic
collapse of the solid inside the source induced by the accumulation of excess
vacancies injected at the orifice. The flux-time curves agree well with a
kinetic model and provide direct information on the diffusivity of vacancies in
solid He.
