Abstract: This work presents the design of a compact embedded 2.45 GHz ECR ion source, including the microwave feed, plasma chamber and the extraction electrode. The overall size of the source is Φ200 mm×178 mm, with a plasma chamber size of Φ30 mm×50 mm. The design parameters of extraction voltage and hydrogen ion current are 50 kV and 20 mA, respectively. The feasibility of the design is verified by simulation. Flow field simulations show that the tri-electrode extraction structure can achieve a 20 mA extracted ion beam at 50 kV, with a beam divergence angle below 1.2×10^-3 rad. The electric field magnitude reaches 4.17 kV/mm under a 50 kV voltage, which is below the breakdown threshold 10 kV/mm of Al₂O₃ material. Thermal simulation results indicate that the as-designed water-cooling structure significantly reduces the maximum surface temperature of the cavity. Simulation results show that the maximum stress of the ceramic chamber is 2.38 MPa under atmospheric pressure with an internal vacuum, which is less than the yield strength (160 MPa) of the Al₂O₃ ceramic material. Based on these results, an ECR ion source system was developed, achieving initial experimental results. Under a vacuum pressure of 5.7×10^-5 Pa, the ceramic cavity did not experience breakdown, and the system demonstrated resistance to voltages exceeding 50 kV. At present, the system successfully outputs a 9 mA hydrogen ion beam at 25 kV.

Key words: ECR ion source, compact design, plasma, extraction electrode