A model for low work function compound deposition on hollow cathode insert surface

The chemistry of the low work function compounds on tungsten emitter surface has been presented qualitatively giving a possible explanation of the 4:1:1 ratio commonly used. The processes involved in BaO deposition and desorption have been described and quantified as well as possible given the chemical data present in the literature producing a simple model for deposition and desorption. The model has then been tested with the ELT NSTAR cathode. The results obtained from the model have been found to be very conservative as expected and a possible explanation has been given stressing the need of a coupled deposition-desorption-plasma model