Injection of Electrons into He II from an Immersed Tungsten Filament

Tungsten filaments have been operated while immersed in He II at temperatures up to 2500°K, and electron currents as high as 0.5 μA have been produced in the superfluid, yielding densities of at least ${10}^9$ negative ions/${\mathrm{cm}}^3$. The fluid in the vicinity of the filament remains quiescent under these conditions as a result of a stable vapor film which forms around the filament.