Structural phase transitions in multipole traps

Mathieu Marciante (1) , Caroline Champenois (1) , Annette Calisti (1) , Martina Knoop (1)

1 PIIM - Physique des interactions ioniques et moléculaires

A small number of laser-cooled ions trapped in a linear radiofrequency multipole trap forms a hollow tube structure. We have studied, by means of molecular dynamics simulations, the structural transition from a double ring to a single ring of ions. We show that the single-ring configuration has the advantage to inhibit the thermal transfer from the rf-excited radial components of the motion to the axial component, allowing to reach the Doppler limit temperature along the direction of the trap axis. Once cooled in this particular configuration, the ions experience an angular dependency of the confinement if the local adiabaticity parameter exceeds the empirical limit. Bunching of the ion structures can then be observed and an analytic expression is proposed to take into account for this behaviour.

Mots clés: rf trap; multipole trap; Coulomb crystal; structural transition; molecular dynamics; simulations

Domaines: Physique Atomique [physics.atom-ph]

Mathieu Marciante, Caroline Champenois, Annette Calisti, Martina Knoop. Structural phase transitions in multipole traps. Applied Physics B - Laser and Optics, 2012, 107, pp.1117. ⟨10.1007/s00340-012-4883-2⟩. ⟨hal-00643625v2⟩