Emittance measurements of electron beams from diamond field emitter arrays

Electron injector technology is presently dominated by a variety of photo- and thermionic electron injectors. Although new electron injectors based on field emission appear promising, their success is predicated on the development of reliable, high current density, low emittance, and spatially uniform, field emitter array cathodes. The authors report recent results of transverse-emittance measurements on a particularly promising cathode, the diamond field emitter array. A simple pepperpot technique is used to measure the divergence of the beam emitted from one such cathode at low current density. Based on these measurements, a 1 mm diameter uniformly emitting cathode will have a normalized transverse emittance of ∼1 mm mrad. Our results suggest that the beam quality of these cathodes is satisfactory for use in a variety of applications.