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This paper aims to summarize the developments of high current H2+ and H3+ ion sources in the past decades. The status of the H2+ and H3+ ion sources is discussed to show the attempts researchers made to improve the beam currents of H2+ and H3+. The results of the 2.45 GHz electron cyclotron resonance ion source named PMECR II at Peking University are presented, which may provide an alternative reference for the design and operation of high current H2+ and H3+ ion sources. [ABSTRACT FROM AUTHOR]

At Peking University (PKU), experimental research as well as theoretical study on how to produce high intense H + , H 2 + , or H 3 + dominated ion beams with a compact permanent magnet 2.45 GHz electron cyclotron resonance (PMECR) ion source have been continuously carried out in the past few decades. Based on the comprehension of hydrogen plasma processes inside a 2.45 GHz PMECR discharge chamber, a three-phase diagram of ion fraction dominant regions that illustrates the relationship between the H + , H 2 + , and H 3 + ion species and working parameters was presented. Meanwhile, a numerical model based on the particle population balance equations was developed for quantitative comprehension of electron cyclotron heated hydrogen plasma. Calculated results of H + , H 2 + , and H 3 + fractions against gas pressure, microwave density, and wall material obtained with this numerical model agree well with the measured ones. Recently, a miniaturized ECR ion source has been developed, and a 52 mA hydrogen beam was extracted. Under the guidance of the model, H + , H 2 + , and H 3 + beams with a fraction of 88%, 80%, and 82%, respectively, were obtained with this miniaturized ECR ion source under suitable working parameters. A PMECR ion source for a proton therapy facility has been built at PKU recently. A 34 mA beam H + fraction of 91% was obtained at the first attempt.