First Operation of an Ungated Diamond Field-Emission Array Cathode in a   L-Band Radiofrequency Electron Source
  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. 
P. Piot, C. A. Brau, B. K. Choi, B. Blomberg, W. E. Gabella, B.   Ivanov, J. Jarvis, M. H. Mendenhall, D. Mihalcea, S. Panug...
physics.acc-ph