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A unified theory of field-, thermo-, and photoemission from metal surface is considered, and the general quantum-mechanical methods for the investigation of the threshold phenomena are applied. As result the corresponding final expressions are obtained in such a form that it is possible to apply immediately the well known methods of scattering theory for their investigation. Thus, a rigorous foundation for existing formula of emission phenomena is given leading to a more exact form and to restrictions of the frames of their applicability without using any concrete model. Some explanations of the emission phenomena which by traditional theory could not be explained, are suggested. Beside this the new approach to emission phenomena permits further generalization.

The non-inductive current drive from directional fast Alfvkn and electron cyclotron waves was measured in the DIII-D tokamak in order to demonstrate these forms of radiofrequency (RF) current drive and to compare the measured efficiencies with theoretical expectations. The fast wave frequency was 8 times the deuterium cyclotron frequency at the plasma centre, while the electron cyclotron wave was at twice the electron cyclotron frequency. Complete noninductive current drive was achieved using a combination of fast wave current drive (FWCD) and electron cyclotron current drive (ECCD) in discharges for which the total plasma current was inductively ramped down from 400 to 170 kA. For steady current discharges, an analysis of the loop voltage revealed up to 195 kA of non-inductive current (out of 310 kA) during combined electron cyclotron and fast wave injection, with a maximum of 110 kA of FWCD and 80 kA of ECCD achieved (not simultaneously). The peakedness of the current profile increased with RF current drive, indicating that the driven current was centrally localized. The FWCD efficiency increased linearly with the central electron temperature as expected; however, the FWCD was severely degraded in low current discharges owing to incomplete fast wave absorption.The measured FWCD agreed with the predictions of a ray tracing code only when a parasitic loss of 4% per pass was included in the modelling along with multiple pass absorption. Enhancement of the second harmonic ECCD efficiency by the toroidal electric field was observed experimentally. The measured ECCD was in good agreement with Fokker-Planck code predictions.

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