Effect of an electric field on superfluid helium scintillation produced by α-particle sources

摘要

We report a study of the intensity and time dependence of scintillation produced by weak α-particle sourcesnin superfluid helium in the presence of an electric field (0–45 kV/cm) in the temperature range of 0.2 to 1.1 K atnthe saturated vapor pressure. Both the prompt and the delayed components of the scintillation exhibit a reductionnin intensity with the application of an electric field. The reduction in the intensity of the prompt component isnwell approximated by a linear dependence on the electric field strength with a reduction of 15% at 45 kV/cm.nWhen analyzed using the Kramers theory of columnar recombination, this electric field dependence leads to thenconclusion that roughly 40% of the scintillation results from species formed from atoms originally promotednto excited states and 60% from excimers created by ionization and subsequent recombination with the chargesninitially having a cylindrical Gaussian distribution about the α track of 60 nm radius. The intensity of the delayedncomponent of the scintillation has a stronger dependence on the electric field strength and on temperature. Thenimplications of these data on the mechanisms affecting scintillation in liquid helium are discussed.