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

Abstract

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. Here, proper damping mechanisms for the repelled particle blobs are necessary to suppress their bounce motions. This stacking method was experimentally proved for electron beams of 1.1 μA. using a Multi-Ring-Electrode trap and the results were compared with numerical estimations based on a single particle model. The observed damping was much larger than the estimated one from the resistive wall effect. The stacking efficiency was nearly the same as the estimated one at the stacked number N less than 1 × 107 but it decreased with N. Experimentally obtained relationship amongst the stacked number, the incident beam energy, the rf frequency and its amplitude behaved qualitatively in the same way as the numerical results. The accumulation proceeded until the well was filled up with electrons. © 2000 The Japan Society of Applied Physics.