Proposed High-Current rf Linear Accelerators with Beams in Thermal Equilibrium

In the conventional design of rf linear accelerators (linacs) the charged-particle bunches are not in three-dimensional thermal equilibrium. For applications requiring high beam currents, the space charge couples the longitudinal and transverse particle motions. This leads to equipartitioning processes which cause unacceptable emittance growth and halo formation. A new design strategy for high-current rf linacs is proposed in which the bunches are in thermal equilibrium so that these effects do not occur. Analytic relationships and scaling laws for the design of such linacs are presented.