An All-Permanent Magnet 10 GHz "Multi-Mode" ECR Ion Source for the Production of Metallic Ions

In order to measure cross sections for charge-changing processes in collisions between ions in our ion-ion [1] experiment one ion beam has to be produced on a high voltage terminal. Since there are restrictions concerning the available space and electrical power an all-permanent magnet 10 GHz electron cyclotron resonance ions source has been built earlier [2]. This ion source is in operation and produces multiply charged ions from gaseous elements with sufficient intensities. Now there is a growing interest in the use of ions from metallic elements. For this purpose a new fully permanent 10 GHz ECR ion source has been constructed and tested. The main feature of this ion source is a stepped plasma chamber (see fig. 1) which allows the propagation of higher microwave modes in the plasma and also results in a bigger plasma volume. The longitudinal magnetic field for the axial plasma confinement is produced by two ring magnets whereas the radial magnetic field is formed by a Halbach-type [3] hexapole magnet. The microwave is produced in a frequency-tunable magnetron (8.75-10.5 GHz, 250 Watt max.) and coupled to the plasma via a coaxial line. The applied microwave frequency turned out to be one of the most important parameters when optimizing the ion source on different charge states since a variation of the magnetic field is not possible with the present configuration.