SURFACE-POTENTIAL OF SMALL PARTICLES CHARGED BY THE MEDIUM-ENERGY ELECTRON-BEAM

The present paper deals with the charging of glass particles of micron sizes by the monoenergetic electron beam with the energy in the range from 400 eV-5 keV. The particles are trapped in an electrodynamic qua drupole placed in an ultra-high vacuum chamber and bombarded by the el ectron beam. The surface of a trapped grain can be modified by the ion beam. The charge of the particles as well as their dimensions are det ermined from the dynamics of their motion inside the quadrupole and th e corresponding surface potential is determined. The equilibrium surfa ce potential is measured for different beam energies and the in fluenc e of the secondary electrons and background electrons on this potentia l is discussed for the grains of different sizes. A simple computer mo del of the charging process which has been developed is able to predic t the equilibrium surface potential. (C) 1998 Elsevier Science Ltd. Al l rights reserved.