A MINICYCLOTRON FOR A SCANNING PROTON MICROPROBE

The isochronous low-energy cyclotron ILEC is a small AVF-machine which has been built for acceleration of protons to a fixed energy of 3 MeV. The total weight of the machine is 3 ton and its power consumption is about 20 kW. Apart from providing an experimental facility for machine research, a main objective of this accelerator project is to produce an intense ion beam with low energy spread for element analysis. For this purpose ILEC is equipped with a double 50-degrees dee system for 2nd harmonic excitation at a frequency of 43.5 MHz and a high voltage amplitude of about 30 kV. To attain the requirement of low energy spread also a double 20-degrees system for 6th harmonic flat topping has been constructed and will be installed soon. During the last year the Eindhoven scanning proton microprobe has been updated. The aim of the new design is to obtain a probe diameter of a few mu-m with a beam current of at least 100 pA. The main application will be the determination of trace elements in biological and medical samples at cellular and subcellular level. In combination with the detection of scattered particles, applications in the field of micro-electronics and materials science are foreseen.