A Transverse-Field-Focussing (TFF) Accelerator for Intense Ribbon Beams

In a TFF Accelerator, a transverse electric field is set up between pairs of curved deflecting plates. Charged particles passing between the plates are both deflected and strongly focussed by the field. Average-straight-line motion (if desired) is obtainable by having the successive pairs of plates curve in alternating directions (with corresponding reversal of the field). Acceleration is achieved by adjusting the mean voltage on each succeeding pair of plates. Computer simulations are in good agreement with the analytically calculated beam dynamics; they show no evidence of beam instabilities and almost no emittance growth. A design for a 400 keV, 8 A/meter, single-ribbon dc accelerator will be presented.