Stacking of a low current electron beam in a harmonic potential trap by rf-repeller

Particles of a low current beam can be accumulated in a harmonic potential well in a high vacuum environment when they are repelled back by a local rf electric field of the frequency close to the bounce motion in the well. He re, proper damping mechanisms for the repelled particle blobs are necessary to suppl ess their bounce motions. This stacking method was experimentally proved for electron beams of 1.1 muA using a Multi-Ring-Electrode trap and the results were compared with numerical estimations based on a single par ticle model. The observed damping was much larger than the estimated one fi om the resistive wall effect. The stacking efficiency was nearly the same as the estimated one at the stacked number N less than 1 x 10(7) but it dec reased with N. Experimentally obtained relationship amongst the stacked num ber, the incident beam energy, the rf frequency and its amplitude behaved q ualitatively in the same way as the numerical results. The accumulation pro ceeded until the well was filled up with electrons.