First two operational years of the electron-beam ion trap charge breeder at the National Superconducting Cyclotron Laboratory

Abstract

The electron-beam ion trap (EBIT) charge breeder of the ReA post-accelerator, located at the National Superconducting Cyclotron Laboratory (Michigan State University), started on-line operation in September 2015. Since then, the EBIT has delivered many pilot beams of stable isotopes and several rare-isotope beams. An operating aspect of the ReA EBIT is the breeding of high charge states to reach high reaccelerated beam energies. Efficiencies in single charge states of more than 20% were measured with ${^{39}\mathrm{K}}^{15+}$, ${^{85}\mathrm{Rb}}^{27+}$, ${^{47}\mathrm{K}}^{17+}$, and ${^{34}\mathrm{Ar}}^{15+}$. Producing high charge states demands long breeding times. This reduces the ejection frequency and, hence, increases the number of ions ejected per pulse. Another operating aspect is the ability to spread the distribution in time of the ejected ion pulses to lower the instantaneous rate delivered to experiments. Pulse widths were stretched from a natural $25\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ up to $\ensuremath{\sim}70\text{ }\text{ }\mathrm{ms}$. This publication reviews the progress of the ReA EBIT system over the years and presents the results of charge-breeding efficiency measurements and pulse-stretching tests obtained with stable- and rare-isotope beams. Studies performed with high sensitivity to identify and quantify stable-isotope contaminants from the EBIT are also presented, along with a novel method for purifying beams.