Radio-frequency quadrupole trap as a tool for experimental beam physics

In recent papers [Okamoto, Hiroshima University Preprint HUBP-01/98 (1998); Okamoto and Tanaka, Nucl. Instr. Meth. A 437 (1999) 178], we proposed a novel experimental approach to investigate various collective effects in space-charge-dominated beams. It was demonstrated that either a radio-frequency quadrupole trap or a solenoidal trap could reproduce non-linear processes equivalent to those in a beam transport channel. In the present work, we study the former trap configuration in more detail, specifying a typical parameter range for beam-physics applications. A three-dimensional Maxwell-equation solver is employed to show the basic characteristics of the plasma confinement field. After deriving several useful formulae, we discuss possible trap experiments that greatly deepen our current understandings of collective beam instabilities including coherent resonances, halo formation, etc.