Harald Giese

Large area multiarc ion beam source 'MAIS'

A pulsed large-area intense ion beam source is described in which the ion-emitting plasma is built up by an array of individual discharge units homogeneously distributed over the surface of a common discharge electrode. A particularly advantageous feature of the source is that for plasma generation and subsequent acceleration of the ions, only one common energy supply is necessary. This allows us to simplify the source design and provides inherent synchronization of plasma production and ion extraction. Results of investigations of the source performance for the production of a proton beam are presented. The maximum beam current achieved to date is on the order of 100 A, with a particle kinetic energy of 15-30 keV and a pulse length in the range of 10 /spl mu/s. Originally conceived for the production of proton beams, the source has recently been modified to allow the production of a metal ion beam. First tests using tungsten ions delivered encouraging results. Future activities will concentrate on the use of alternative-metal ions, carbon ions, and beams composed of mixed ion species.

High power particle beams and pulsed power for industrial applications

Several industrial scale projects with economic and ecologic potential are presently emanating from research and development in the fields of high power particle beams and pulsed power in Europe. Material surface modifications with large area pulsed electron beams are used to protect high temperature gas turbine blades and steel structures in Pb/Bi cooled accelerator driven nuclear reactor systems against oxidation and corrosion respectively. Channel spark electron beams are applied to deposit bio-compatible or bio-active layers on medical implants. Cell membranes are perforated with strong pulsed electric fields to extract nutritive substances or raw materials from the cells and to kill bacteria for sterilization of liquids. Eletrodynamic fragmentation devices are developed to reutilize concrete aggregates for the production of high quality secondary concrete. All activities have a large potential to contribute to a more sustainable economy.

Investigation of large-area multiarc pulsed ion source plasma parameters

Using plasma probes of different geometries and spectroscopic methods, crucial plasma parameters like electron temperature, plasma density and plasma potential were measured on a multiarc large area ion source (MAIS). MAIS is a pulsed source of plane geometry and circular circumference, in which the ion emitting plasma is built up by the synchronous ignition of an array of 180 individual discharge units. The total current through all discharge units was varied in the range of 100-300 A. The pulse duration was of the order of z=30 A and the applied acceleration voltage U=10-20 kV. Plasma parameters assessed by these measurements were as follows: electron temperature near the anode (extractor) grid 10-30 eV; in the spark region /spl ges/4 eV. The electron density n, near the anode grid is in the range of 10/sup 11/ cm/sup -3/ (depending on discharge current, the radial coordinate and on the potential of the anode grid), in the spark region /spl ges/5/spl times/10 cm/sup -1/. The plasma potential lies in the range of 50-70 V.