Towards high brightness electron beams from multifilamentaryNb3Snwire photocathode

Abstract

In order to find electron sources of low emittance and high quantum efficiency, single tip cathodes with a microstructured surface are investigated. Emission currents up to 310 A were obtained, by combining a 2 ns, 50 kV accelerating voltage pulse with a 266 nm wavelength, picosecond ( t ¼ 6:2 ps) laser delivering a few J pulse energy. The multifilamentary cylindric Nb 3 Sn tip with a typical diameter of 0.8 mm provides quantum efficiencies up to 0.5%. The microstructured needle has also been tested in a combined diode-rf electron gun with 500 kV, 250 ns pulsed bias voltage as a first step towards reducing emittance-spoiling space-charge forces.

Characterisation of Pb thin films prepared by the nanosecond pulsed laser deposition technique for photocathode application

“…Such features, in fact, could improve the photoemission performances of the cathode by the field emission effect [27][28][29] but the formation of large voids and holes on the film surface limits the application of such a device as a cathode. Further studies will be required in the future to improve the morphology of cathodes based on nanostructured Pb thin film.…”