Laboratory Studies of Electric Charging of Dust Particles

Abstract

In an electrodynamic quadrupole inside an ultra-high-vacuum chamber, glass particles of micron sizes were suspended and charged by electron and ion beams of energies up to 5 keV. The temporal dependencies of the particle Q/M-ratios, surface potentials, electric field strengths and charging currents were obtained. The sticking coefficients of the primary electrons and ions on the particle surface were estimated. We also calculated the energy spectrum of secondary electrons emitted from the particle surface. During charging by ions, a discharging effect probably due to a field emission of ions from the surface of the particle was found. Since we see such an emission at much lower field strengths than we expected, the equilibrium surface potentials of very small (or irregularly-shaped) particles may be lower than former theoretical estimates predict.