The mean lifetime of a particle diffusing in a cylindrical cavity with a circular absorbing spot on the cavity wall is studied analytically as a function of the spot radius, its location on the wall, the particle initial position, and the cavity shape determined by its length and radius. When the spot radius tends to zero our formulas for the mean lifetime reduce to the result given by the solu...

Recent investigations on the collapse and growth of macroscopic cavity regions in a granular material due to viscous flow have revealed the possible mechanism of the occurrence of natural disasters such as landslides, collapses of riverbanks and cliffs. We have already shown both theoretically and experimentally a significant effect of flow concentration into the macroscopic cavity regions in a...

For high current applications, it is desirable for the cavity shape to have a low longitudinal loss factor and to have a high beam-breakup threshold current. This paper briefly describes three different cavities designed for this purpose: a six-cell elliptical cavity for particles traveling at the speed of light, a two-cell elliptical cavity for subluminal particle speeds, and a single cell cav...