Monte Carlo simulation, analytical and experimental studies on the nozzle structure of a Cs vapour delivery system for negative ion sources

•Maintaining a well-controlled coverage of cesium on the plasma grid of a negative ion source is a key issue for the neutral beam heating systems on ITER.•This paper gives a clear account of the application of detailed experimental measurements and modeling tools and shows these may be used to optimize the Cs deposition process.•This would be a useful reference for those developing neutral beam systems and negative ion sources for fusion and other applications.•This paper deals with the study of nozzle structure optimization for controlled Cs evaporation and deposition into fusion grade ion source.