Preliminary Results of H2 Beam Generated by a 2.45 Ghz Permanent Magnet Ecr Ion Source at Pku*

To obtain high-yield H2 ion beam, experimental and theoretical study was carried out on the 2.45 GHz Peking University permanent magnet electron cyclotron resonance ion source (PKU PMECRIS). With PMECR II [1], studies on the size of discharge chamber and the operation pressure were carried out to increase H2 ion fraction. Beam analysis results prove that the H2 can reach 47.7% with suitable operation parameters. More details will be presented in this paper. INTRODUCTION The creation of molecular ion H2 is an essential process in hydrogen gas plasma. For proton ion source, H2 ions are undesirable in the final extract beam. But recently, the demand to build an ion source to generate high current hydrogen molecular ion H2 beam has been growing rapidly. For example, H2 ion can be used as a pilot beam of the intense deuteron beam during the commissioning of linear accelerators to minimize the activation of components.[2][3] Also it is an effective way to improve the output current of cyclotrons by accelerating H2 and stripping it into H at the exit of accelerator, instead of accelerating H beam directly.[4][5] R. F. King et al. proposed a one-dimensional plasma model for a volume arc source, which is expected to produce 140 mA of ion beam with H2 species ratio around 73% in theory, but it wasn’t realized.[6] N. Joshi et al. developed a volume type ion source at Frankfurt University, and about 91% H2 was extracted with current intensity of 2.84 mA.[7] Obviously, the fraction of H2 is definitely high, but the current is not enough for some applications. With a 2.45 GHz permanent magnet ECR ion source PMECR II [1][8][9] (Fig. 1), the fraction and current intensity of molecular ion H2 were improved at PKU. Theoretical study indicates that, to optimize the production of H2, it is helpful to increase the electron temperature in the source and avoid attachment with neutral H2 which lead to fast destruction of H2.[6] In our PMECRIS, these were achieved by changing the size of discharge chamber and operation pressure in the source. The experimental results will be presented.