Velvet''s multi-pulsed emission and multi-pulsed electron beams
Velvet＇s multi-pulsed emission and multi-pulsed electron beams

The velvet electron emission characteristics and beams' brightness are investigated with a multi-pulsed mode. The results indicate that in the multi-pulsed mode the velvet emission is not uniform and the periphery emission is much stronger than that from the centre. The periphery emission contributes much more to the formation of the cathode plasma than the centre emission, which leads to diode impendence breakdown. The relationship between the cathode plasma expansion and the initial emittance of the cathode is deduced to describe the characteristics of the multi-pulsed vacuum diode. The emittance of the multi-pulsed beams is measured to be less than 1000mm \cdot mrad. The brightness of the electron beams is better than 1\times 10^{8}A/(m \cdot rad)^{2}.