Intense beams of micro-particles, each attached with approximately 1.1 × 10 7 electrons, were generated repeatedly. The particle was a spherical divinyl benzene polymer of 10 µm diameter, coated with 450Ȧ thick gold. More than 5000 charged particles were extracted outside in 0.5 s using an assembly composed of a reservoir, a helicoid conveyer, an oscillating sawtoothed plate and a charging section of a high electric field.