Charge breeding of isotope on-line-created radioactive ions using an electron cyclotron resonance ion trap

Abstract

In the coming years huge ion-beam projects are foreseen. They deal with specific isotope on-line (ISOL) beams such as ISOL-created radioactive ions. The beam intensities are exceptionally high (>1012ions∕s), the radioactive lifetimes are short (⩽1s), and the ion energy is very high (⩾150GeV∕u). In general in order to minimize the size of the accelerator one needs highly charged ISOL ions and therefore charge breeders are a must. In contrast with the CERN system, utilizing a Penning trap and an electron-beam ion source charge breeder (where the maximum ion beam cannot exceed 106ions∕s) the Grenoble group launched in 1995 an electron cyclotron resonance (ECR) system capable of storing 1012ions∕s and delivering highly charged ISOL ions. In this article we show that this storage is possible for low-ion-energy ISOL ions following classical slowing down theory. In this case the injected ISOL ions are slowed down by ion-ion collisions which yield ion storage inside the ECR plasma, but also charge breeding by the energetic ECR electrons bombarding the slowed down ions.