Electron Emission in Superfluid and Low-temperature Vapor Phase Helium
  Tungsten filaments used as sources of electrons in a low temperature liquid or gaseous helium environment have remarkable properties of operating at thousands of degrees Kelvin in surroundings at temperatures of order 1 K. We provide an explanation of this performance in terms of important changes in the thermal transport mechanisms. The behavior can be cast as a first-order phase transition. 
Isaac F. Silvera, Jacques Tempere