The electron cyclotron resonance (ECR) charge state breeding method based on the PHOENIX source is first dedicated to the continuous high charge state radioactive ion production for cyclotrons, due to their q/m requirements, and to the high charge state production efficiency. It can be used as an injector for RFQ, linacs, and synchrotrons either in cw or pulsed operation. The efficiency of the 1+ to the n+ ion production and the charge breeding time are the fundamental parameters of the method, their dependence with regard to the 1+ ion beam emittance injected has been measured and will be discussed with regard to the radioactive ion beam acceleration. The efficiency of the process slightly decreases when injecting ion beam emittances higher than 30 π mm mrad, and remains constant in the 1+ radioactive intensity range available today and in the future. The ECR ion trap tuning associated with the afterglow mode permits the ionization, the accumulation, and the extraction of the injected primary beam keeping interesting efficiencies suitable to pulsed accelerators. © 2002 American Institute of Physics.