Simulation Study of Emittance Growth from Coulomb Collisions in Low-Temperature Ion Beams

Abstract

We systematically investigate the collisional heating process of space-charge-dominated coasting ion beams in a storage ring using the molecular dynamics simulation technique. To evaluate the heating rate over the whole temperature range, we start from an ultralow-emittance state where the beam is Coulomb crystallized, apply perturbation to it, and follow the emittance evolution until the beam comes to a regular high-temperature state. The dependence of the heating behavior on various machine and beam parameters, such as the line density, betatron tune, kinetic energy, mass number, and charge state of ions, is explored systematically. The parameter dependence of the heating behavior can be combined, in several cases, into the Coulomb coupling constant. An approximate formula is given for the magnitude of emittance at which the collisional heating is maximized.