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Negative ion sources and the mechanisms for negative ion production are reviewed. Several classes of sources with surface origin of negative ions are examined in detail: surface-plasma sources where ion production occurs on the electrode in contact with the plasma, and ‘‘pure surface’’ sources where ion production occurs due to conversion or desorption processes. Negative ion production by backscattering, impact desorption, and electron- and photo-stimulated desorption are discussed. The experimental efficiencies of intense surface negative ion production realized on electrodes contacted with hydrogen-cesium or pure hydrogen gas-discharge plasma are compared. Recent modifications of surface-plasma sources developed for accelerator and fusion applications are reviewed in detail.

A review of investigations in the physics and technology of ion sources, developed in the Institute of Nuclear Physics in Novosibirsk is presented. Distinctive features of physical processes and technical characteristics of plasma sources of gaseous ions, negative ion surface-plasma sources, electrohydrodynamic (liquid metal) ion sources are considered. In original design plasma sources, ion beams with a current of up to 90 A and energies 1–30 keV are formed by four-electrode multislit extraction systems from highly ionized, high brightness plasma flux, generated by an high-current arc discharge with a cold cathode in a small cross-section diaphragmed channel, and directed with a magnetic field of a special configuration. Plasma jet expansion for a very low ion temperature (0.1 eV) production is used. In surface plasma sources, the fluxes of negative ions are produced when electrons are captured from the electrode surface at the electron affinity level of sputtered and reflected particles. A discharge of a special type in a gas-cesium mixture with in a thin plasma layer between the negative ion emitter and emission holes is used. A number of versions of SPS with different types of discharges are considered: SPS which operate in pulse mode with H− beam current up to 11 A, with current 0.1 A, and high brightness for accelerators, for continuous mode operation. Specific features of physical processes in electrohydrodynamic (EHD) ion emitters are studied and the technology of production of different ions is worked out. The production of ion beams with high brightness from the dielectric melt in the EHD-emission regime is developed. The dynamics of spontaneous oscillation excitation with a quasidiscrete spectrum in the frequency range of up to 108 Hz, transient processes occurring at the emission disturbances, emission stability at low current, a physical model for calculating the emission surface dimensions, and the evolution of the ion momentum distribution function for the ion motion are studied. The utilization of the designed EHD sources in the ion microscope, in submicromachining and in high voltage accelerators are discussed.

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