Investigations of the new Giessen 10 GHz electron-cyclotron-resonance ion source

Abstract

A 10 GHz electron-cyclotron-resonance (ECR) ion source has been designed and built to extend our studies of the collisions of highly charged ions with electrons. The magnetic system of the ion source consists of three solenoid coils for the axial field component and a hexapole permanent magnet for the radial field component. A 10 GHz microwave system supplies up to 2.5 kW of microwave power to the plasma. The ion source can be operated at a high voltage potential of 20 kV and yields total ion currents of 0.2–2.5 mA. Ion beams produced with argon, oxygen and xenon were analyzed by a dipole magnet. Substantial currents up to O 7+, Ar 11+ and Xe 27+ were measured. Furthermore, newly recognized properties of the extracted ion beams were obtained from electron-impact ionization studies. A strong correlation between the electron-impact ionization cross section in the supplied microwave power level resulted in a significantly higher ionization cross section of the reaction O 5+ + e − → O 6+ +2e −. Multiply charged ions from ECR ion sources would appear to have a “memory” of the conditions of their production.