Generation, growth and collapse of bubbles on collision of particle with electrode in Dc electrically stressed liquid helium

摘要

The paper deals with the bubble formation process in the presence of a free conducting particle in liquid helium to understand the electrical insulation environment in pool cooled superconducting devices under particle contaminated conditions. Experiments were conducted with dc stressed parallel plane electrodes containing a free spherical metallic particle of lmm radius in saturated normal and saturated superfluid helium. Experimental results show that a single bubble is always generated at the moment of particle collision with the electrode and the bubble behavior depends strongly on the state of the liquid helium. The bubble expanding and shrinking processes were analyzed on the basis of energy balance among released electrostatic and kinetic energies of the particle at the moment of particle collision with the electrode, kinetic energy of liquid driven by bubble growth, work done on environmental pressure and internal energy of the bubble gas. The analysis shows a fairly good agreement with experiments.