Abstract
A novel S-Band Micro-Pulse electron Gun (MPG) which works at the left crossover point energy EcI on the Secondary Electron Yield (SEY) curve was proposed. The working principles of the MPG were presented. The maximum output beam current limited by space charge effects and beam loading effects was investigated by theoretical analysis. The result shows that the maximum beam current is decided by the parameters of the MPG such as resonant frequency, cavity length, shunt impedance and the secondary emission property of the cathode and grid, having nothing to do with the power flowed into the cavity. The low shunt impedance and the low slope of the SEY curve can help increasing the maximum beam current. According to the principles, a MPG with the frequency of 2.856 GHz has been designed and constructed. The steady working state was achieved by using oxygen free copper and molybdenum grid with different transmission coefficient. It was found a good agreement between the analysis and the experiments.
Highlights
The phenomenon of the electron emission including electron bombardment was discovered by Austin and Starke[1] in 1902 during a study of the reflection of electrons from metals
In order to obtain high beam current, most of the studies concentrate on the development of high radio frequency (RF) power Micro-Pulse electron Gun (MPG) which generally works on the right side of the Secondary Electron Yield (SEY) curve
A novel S-band Micro-Pulse electron Gun (MPG) was proposed. This kind of MPG shortens the length between the grid and the emission surface and works at the left crossover energy EcI on the total SEY curve that distinguishes from others
Summary
The phenomenon of the electron emission including electron bombardment was discovered by Austin and Starke[1] in 1902 during a study of the reflection of electrons from metals. Due to its self-bunching property and the high RF frequency, MPG is capable of providing high repetition rate and short pulse electron beams. These features make MPG one of the appropriate electron sources for Free Electron Laser (FEL), frequency locked Coherent Smith-Purcell Radiation (CSPR) which makes it an active research area.[20,21,22,23,24,25] in order to obtain high beam current, most of the studies concentrate on the development of high RF power MPG which generally works on the right side of the Secondary Electron Yield (SEY) curve.
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