FIELD-EMISSION AND SURFACE CONDITIONING

Vacuum breakdown is known to be the major limitation to the obtention of high electric fields in devices like klystrons or accelerating rf cavities. As a precursor to breakdown, electronic field emission has triggered much interest in fundamental as well as in applied research. The present paper describes some recent experimental results on enhanced field emission from extended metallic surfaces. interpretation of these results favours the rehabilitation of the old geometrical model explaining the enhancement of field emission in terms of field amplification on sharp conducting protrusions. A few plausible remedies are discussed, with special emphasis on the case of field emission from superconducting rf cavities.