A Gold Needle Tip Array Ultrafast Electron Source with High Beam Quality

Nanometer-sharp needle tips are the electron sources with the highest beam quality. However, for a single needle tip, the total emission current is limited. Combining multiple needles into an array of tips should allow for higher currents while preserving the properties of the individual emitters. Previous studies on tip arrays have shown impressive emission character-istics, but could not demonstrate favourable transversal beam properties such as a well-behaved spot shape or low emittance. Here, we introduce an ultrafast electron source composed of a lithographically fabricated array of nanometer-sharp gold tips illuminated by 25 fs laser pulses. By harnessing the emission of multiple needles, we achieve a high-current electron beam while preserving individual emitter properties. Our source delivers up to 2000 electrons per pulse at moderate laser peak intensities of 10
¹¹
w /cm
²
, with a narrow energy width of 0.5 ± 0.05 eV and a well-behaved Gaussian profile. The resulting electron beam exhibits high collimation and a small normalized emittance on the order of nm.rad, making it ideal for applications requiring both high current and spatial resolution, such as free-electron light sources and chip-based particle accelerators.