Pulsed field emitted current from different commercial samples in the purpose of a free electron laser application

The development of an electron gun with the lowest possible emittance would help reduce the total length and cost of a free electron laser. Recent progress in vacuum microelectronics makes field emitter tips an attractive technology to explore for high brightness electron sources. In order to be a good candidate for a low emittance gun, field emission cathodes must provide at least the peak current, stability, and homogeneity of current state of the art electron sources. In this article, we report on current voltage measurements of commercially available field emitter samples in both continuous and pulsed mode. Pulsed electron emission is of particular interest for a free electron laser application. As mentioned by other authors [F. Charbonnier, Appl. Surf. Sci. 94/95, 26 (1996); P. R. Schwoebol et al., J. Vac. Sci. Technol B 19, 980 (2001)], higher peak current and more stable emission can be achieved when using short square voltage pulses at low frequency. We present maximum peak currents achieved with 100 ns long voltage pulses at low frequency (50 Hz). In such a pulsed mode, the risk of excessive heating and cathode damaging is considerably reduced.