A global model of 2.45 GHz ECR ion sources for high intensity H+, H2+ and H3+ beams

The 2.45 GHz electron cyclotron resonance ion source (ECRIS) is recognized as one of the most efficient devices for the production of high intensity H+, H-2(+) and H-3(+) beams. To elucidate the mechanism of electron cyclotron heated (ECH) hydrogen plasma, a global model based on the energy and particle balance equations is developed at Peking University (PKU). This model is applied to a permanent magnet ECRIS named PMECR II at PKU to study the dependences of the H+, H-2(+), and H-3(+) ion fractions of the extracted beam on the gas pressure, microwave power, wall material and chamber diameter. The calculated results obtained with the global model are in good agreement with the experimental results. Moreover, a more compact 2.45 GHz ECR ion source is designed and operated under the guidance of the model for the generation of H+, H-2(+) and H-3(+) ion dominated beams. Beams with H+, H-2(+) and H-3(+) ion fractions greater than 80% were produced under optimized gas pressure and microwave power with this new ECR source.