Performance of a new compact ECR ion source for stable isotope mass spectrometry

We have developed a mass spectrometry system, known as the IRMS⁺⁺, for measurement of isotope ratios of the light elements carbon, nitrogen and oxygen, for applications in earth and environmental sciences. By generating multiply-charged atomic ions from molecular gaseous species, such as water vapour or carbon dioxide gas, isotopes can be measured free from molecular interferences [1]. The IRMS⁺⁺ uses an ECR ion source specially designed for this purpose [2]. The new ECRIS design incorporates improvements to the microwave system, with special attention to generation of the cavity mode which is expected to couple most effectively to electrons in the ECR resonance zone. Also this design has an improved magnetic field structure to optimise performance at 7GHz. In this paper we will report initial performance tests of the new ion source.