An Ultra-Bright Pulsed Electron Beam with Low Longitudinal Emittance

Most existing electron sources extract electrons from conductors. Since the actual temperature inside the conductor is much less than the Fermi temperature of the conduction electrons, the electron degeneracy δfis close to 1, the maximum allowed by the Pauli exclusion principle. However, during extraction several factors conspire together to reduce δfmany orders of magnitude, limiting the achieved values to ≈ 10⁻⁵. A new concept is described for building a novel electron source designed to produce a pulsed beam with δf≈ 2 10⁻³and longitudinal emittance four orders of magnitude smaller than currently achieved values. This high brightness, low longitudinal emittance regime enables a wide range of novel applications that utilize angstrom-scale spatial resolution and eV-scale energy resolution. The current state of a proof-of-principle experiment conducted at LBNL is also described.