Multiple charge ion beam generation with a 2.45 GHz electron cyclotron resonance ion source

Multiple charge ions （MCIs） are necessary for increasing the output energy of particles in accelerators. In general, MCI beams are largely produced by electron beam ion source （EBIS） [1], laser ion source （LIS） [2], or high-frequency （mostly 〉5 GHz） electron cyclotron resonance （ECR） ion source [3]. Among these, only ECR ion source can operate in the continuous wave （CW） mode, while EBIS and LIS only support pulses. In addition, ECR ion source with lower frequency （mostly 2.45 GHz） are required primarily for generating single charge state ions, because the corresponding ECR field （875 Gs） is not sufficiently strong for MCI generation [4].