Purification of radioactive neutron-rich argon beams using an ion source in charge breeding mode

Measurements of nuclear properties of some neutron-rich asymmetric fission isotopes at an ISOL laboratory present a severe problem when a plasma ion source is used as the primary ion-source. The problem is associated with intense multi-charged symmetric fission contaminants that cannot be mass-separated from asymmetric fission products. In this work we demonstrate how this problem can be overcome on-line by using an electron cyclotron resonance ion source (ECRIS) as a charge-breeding secondary ion-source. Mixed Ar$^{+}$, Kr$^{2+}$, Xe$^{3+}$ radioactive beams from an plasma ion-source were injected into the PHOENIX ECRIS that currently is installed at the ISOLDE facility at CERN in order to improve the ratio of Ar to the background contaminants of Kr and Xe. The signal to noise ratio was improved by more than two orders of magnitude after charge-breeding and mass-separation of the Ar$^{8+}$, Ar$^{9+}$ beams. The information on the decay of the $^{48}$Ar nucleus obtained in these tests is useful for a better understanding of the origin of the $^{48}$Ca, $^{46}$Ca meteorite isotopic anomaly. Potential applications of the method are discussed.