Resistive cooling of highly charged ions in a Penning trap to a fluid-like state

Abstract

We have performed a detailed experimental study of resistive cooling of large ensembles of highly charged ions such as Ar${}^{13+}$ in a cryogenic Penning trap. Different from the measurements reported in [M. Vogel et al., Phys. Rev. A, 043412 (2014)], we observe purely exponential cooling behavior when conditions are chosen to allow collisional thermalization of the ions. We provide evidence that in this situation, resistive cooling time constants and final temperatures are independent of the initial ion energy, and that the cooling time constant of a thermalized ion ensemble is identical to the single-ion cooling time constant. For sufficiently high ion number densities, our measurements show discontinuities in the spectra of motional resonances which indicate a transition of the ion ensemble to a fluid-like state when cooled to temperatures below approximately 14 K. With the final ion temperature presently being 7.5 K, ions of the highest charge states are expected to form ion crystals by mere resistive cooling, in particular not requiring the use of laser cooling.

References in corpus (5)

• HITRAP: A facility at GSI for highly charged ions
• Experimental access to higher-order Zeeman effects by precision spectroscopy of highly charged ions in a Penning trap
• Electronic detection of charged particle effects in a Penning trap
• Resistive and sympathetic cooling of highly-charged-ion clouds in a Penning trap
• Optically transparent solid electrodes for precision Penning traps

Cited by in corpus (2)

• Production of highly charged ions inside a cryogenic Penning trap by electron-impact ionisation
• Towards metrology with highly charged isomeric ions from antiproton annihilation