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A compact Paul ion trap for the study of space-charge effects in drift-tube linear accelerators


 Starting from the principle of least action, we derive a general Hamiltonian that describes the collective motion of an intense charged-particle bunch in a drift-tube linear accelerator. The Alvarez-type structure is assumed as an example, but the present theory can readily be extended to other types of conventional linacs. A Hamiltonian formalism of non-neutral plasma in a linear Paul trap is also constructed, which demonstrates clear similarity between the linac system and compact ion-trap system. The physical equivalence between these two dynamical systems can be employed to perform a fundamental design study of high-intensity hadron linacs in a local tabletop environment. For the tabletop experiment on space-charge effects in short proton and heavy-ion bunches, we have designed an ion trap whose overall dimension is less than 10 cm axially and whose aperture size is 1 cm in diameter. The new trap is introduced in the S-POD (Simulator of Particle Orbit Dynamics) apparatus developed at Hiroshima University for “Laboratory Accelerator Physics.”