INSTABILITIES OF ION CONFINEMENT IN A PENNING TRAP

We have observed rapid ion loss from a Penning trap at certain operati ng conditions. Here the ratio of the cyclotron or axial oscillation fr equency is an integer multiple of the ''metastable'' magnetron frequen cy. Higher-order contributions to the ideal quadrupole trapping potent ial causes energy transfer into the magnetron motion, whose orbit incr eases. This effect is analogous to the stop bands observed in accelera tors and storage rings.