  In this paper, we present the results of experimental observation of
strong-field photoemission from a diamond field-emitter array (DFEA)
illuminated by a focused laser beam with 1035 nm wavelength. Having the
advantage of high emission current and low beam emittance, DFEAs can emit
ultra-short high charge electron bunches required for multiple accelerator
applications. We have performed strong-field photoemission experiment at a
newly commissioned test stand at Los Alamos National Laboratory (LANL). We
triggered a diamond tip with a typical apex of 10-20 nm with 300 femtosecond
(fs) laser pulses to produce electron beam emission. The profile of the emitted
beam was determined by the analysis of an image formed on the fluorescent
screen after a microchannel plate (MCP) intensifier; beamlets corresponding to
emission from the pyramid sides and nano-tip were identified. Image analysis of
the beamlet associated with emission from the nano-tip was conducted to
understand dependencies of intensities of the emission on polarization of the
laser's light and its peak intensity.
