Optimization of electron beams for ion bombardment secondary emission electron gun

Electron beam fluorescence technology is an advanced non-contact measurement in rarefied flow fields, and the fluorescence signal intensity is positively correlated with the electron beam current. The ion bombardment secondary emission electron gun is suitable for the technology. To enhance the beam current, COMSOL simulations and analyses were conducted to examine plasma density distribution in the discharge chamber under the effects of various conditions and the electric field distribution between the cathode and the spacer gap. The anode shape and discharge pressure conditions were optimized to increase plasma density. Additionally, an improved spacer structure was designed with the dual purpose of enhancing the electric field distribution between the cathode-spacer gaps and improving vacuum differential effects. This design modification aims to increase the pass rate of secondary electrons. Both simulation and experimental results demonstrated that the performance of the optimized electron gun was effectively enhanced. When the electrode voltage remains constant and the discharge gas pressure is adjusted to around 8 Pa, the maximum beam current was increased from 0.9 mA to 1.6 mA.