Charge breeding techniques

The numerous newly built and forthcoming post-accelerators for radioactive ions, produced with the isotope separator on-line (ISOL) technique, all have a need for an efficient method to accelerate the precious primary ions. The traditional foil or gas stripping technique was challenged some five to ten years ago by a novel scheme called charge breeding. The transformation from 1(+) to n(+) charged ions takes place inside an Electron Beam Ion Source/Trap (EBIS/T) or Electron Cyclotron Resonance Ion Source/Trap (ECRIS/T) by electron-ion collisions. These charge breeders are located in the low-energy part of the machine before the accelerating structures. Because of the capability of these devices to produce highly charged ions, charge-to-mass ratios between 1/9 and 1/4 are easily obtained. In this article the performance and the features of the two charge breeding concepts will be compared and discussed. An outlook on charge breeders for the next generation of radioactive ion beam facilities is also given.