Development of a charge breeding system with two electron cyclotron resonance ion sources

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The purpose of this research was to develop a charge breeding system by employing two electron cyclotron resonance (ECR) ion sources. The singly charged ions extracted from the first ECR ion source, are injected into the second ECR ion source called charge breeder after being decelerated down to a proper energy. Then ions, externally injected in this way, are almost completely stopped and trapped in the plasma of the charge breeder through frequent small angle scatterings by plasma ions. Subsequently, they are ionized to higher charge states, which could be extracted again from the breeder. In order to understand the stopping process, at first, we have develop a computer program to handle collision processes between injected energetic ions and plasma ions under the magnetic field of the ECR ion source, finally giving a stopping efficiency under well-defined conditions such as plasma volume, density, temperature and most probable charge states of plasma ions. Secondly, we have made a step-by-step decelerating system, which was used to decelerate ions just before injecting into the ECR plasma. We have performed an experiment to inject singly charged Ar ions into the second ECR ion source. The breeding efficiency in total was about 16%, and the efficiency for 5+ or 6+ Ar ions was around 2%. The experiment is still going on in order to improve the breeding efficiency as well as to understand systematically the efficiency.