Research of Cesium Adsorption on Mo and Ni Based on Temperature-Controlled Quartz Microbalance

The appropriate cesium adsorption on the converter (plasma grid) in the negative ion source is expected to lower surface work function, thus enhancing negative ion production and decreasing the ratio of co-extracted electrons. The cesium coverage process is important in understanding cesium dynamics and provides input parameters for simulation of cesium-wall interaction. The cesium coverage model based on Langmuir theory is established with analytical solution. Based on temperature-controlled quartz microbalance (QMB), experiments are carried out on different crystals under various cesium flux and surface temperatures, to simulate the actual cesium injection environment in negative ion sources. The experimental data are analyzed and compared with the fitting curves of cesium coverage theoretical model. The results show the influence of surface temperatures and materials on cesium adsorption, along with the sticking coefficients calculated.