ION BEAMS

The experimental results of highly charged ion beam transport with space charge compensation by electrons are presented. A tungsten thermionic cathode has been used as a source of electrons for beam compensation. An enhancement factor in ion current density of 8- 10 is obtained for an extraction voltage of 40 kV, while a factor of 3- 5 is obtained for an extraction voltage of 60 kV. The transport distance was 1.2 m. Special attention is given to recombination processes in an ion beam with a high degree of compensation. Charge states and energy distributions were deduced from the beam distributions measured with a micro-channel plate (MCP), with a phosphor screen and CCD-camera, after the bending magnet. Significant recombination, for highly charged ions, was observed due to the thermoelectrons. The experimental work was performed at CERN