  We report on the first successful operation of a field-emitter-array cathode
in a conventional L-band radio-frequency electron source. The cathode consisted
of an array of $\sim 10^6$ diamond diamond tips on pyramids. Maximum current on
the order of 15~mA were reached and the cathode did not show appreciable signs
of fatigue after weeks of operation. The measured Fowler-Nordheim
characteristics, transverse beam density, and current stability are discussed.
Numerical simulations of the beam dynamics are also presented.
