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

Trassl R., Broetz F., Pawlowsky M., Arnold W., McCullough R. W.* and Salzborn E.
Institut fuer Kernphysik, Justus-Liebig-Universitaet Giessen, Leihgesterner Weg 217, 35392 Giessen, Germany

*Department of Pure and Applied Physics, Queen's University of Belfast, Northern Ireland

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.

Figure 1 : Mechanical set-up of the 10 GHz "multi-mode" ECR ion source

Attached to the coaxial line is either a bundle of wires where metal atoms with high melting points can be sputtered from or an evaporation oven for metallic elements with low melting points. A detailed description of the ion source and first results for the metallic ion production using the oven technique will be presented at the conference. The ion source was already successfully operated at the ion-ion-experiment delivering a Bi4+-ion beam with both an excellent reproducibility and a very good stability (about 100 h until the evaporation oven had to be refilled).

[1] S. Meuser et al, Rev. Sci. Instrum. 67 (8), 1996
[2] R. Trassl et al, Physica Scripta, Vol. T73, 380-381, 1997
[3] K. Halbach, Nucl. Instr. Meth. 169, 1 (1980)

Presenting Author : Broetz F.
Presentation : Poster
Wednesday Poster Session at 14:45