  Nanosecond electron pulses are appealing for ultrafast imaging and electron
gating applications, where tunable currents and narrow energy spreads are
desirable. Here, we demonstrate photoemission from a Schottky emitter triggered
by nanosecond laser pulses and use a dispersive magnetic prism array to image
the electron energy distributions. Using photon energies optimally tuned to the
emission potential barrier, we generate pulses containing over 10$^5$ electrons
with energy spreads below 1 eV with a prompt, single-photon emission process.
These results are consistent with theoretical models of laser-triggered
electron emission and energetic broadening during propagation and can be widely
implemented.
