Design and optimization of a tetrode extraction system using IBsimu and CST for a multi-cusp proton ion source

Abstract Achieving low-emittance, high-intensity beams remains a critical challenge for next-generation high intensity proton accelerators. This paper presents a comprehensive design and advanced simulation analysis of a compact tetrode extraction system for a novel 2.45 GHz multi-cusp Electron Cyclotron Resonance (ECR) proton source developed as a parallel injector for Medium Energy High Intensity Proton Accelerator (MEHIPA). The system utilizes a zero-axial-field configuration to minimize magnetic contributions to the beam emittance. A dual-simulation methodology is implemented: IBsimu is used for initial geometric optimization and parametric analysis, followed by detailed studies of multi-species extracted beam in CST Microwave Studio (MWS) and the integration of Monte Carlo Collision (MCC) modelling in its Particle Tracking Solver (PTS). This combined approach allows accurate modelling and provides a better visualisation of complex phenomena, including multi-species co-extraction and the crucial effects of space-charge compensation (SCC) on the extracted beam. The optimized compact tetrode geometry (total length ~ 45 mm) is capable of delivering 12–15 mA of H + current at 30 keV with a normalised emittance of 0.1 π-mm-mrad. These results provide detailed design insights and optimization strategies that can guide the development of high brightness ion sources with optimized beam quality.