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Physics of Surface-Plasma H Ion Sources

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Physics and Applications of Hydrogen Negative Ion Sources

Part of the book series: Springer Series on Atomic, Optical, and Plasma Physics ((SSAOPP,volume 124))

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Abstract

Surface-plasma sources (SPS) deliver intense and bright negative ion (NI) beams for accelerators and fusion plasma neutral beam heating systems. High efficiency of SPS is achieved by the proper combination of plasma and electrode surfaces in gas discharge devices optimized for NI production, transport, and extraction. Plasma provides an intense bombardment of discharge electrodes by “primary” energetic particles: hyperthermal atoms and positive ions. The near-electrode potential sheath of gas discharge pre-accelerates the primary positive ions to the NI production electrode and extracts the produced NI flux back to the plasma—where NIs are transported to the extraction apertures. The self-adjusting thickness of the gas discharge near-electrode potential sheath permits pre-acceleration of the primary positive ion flux and the secondary NI flux without a space-charge limit. The decrease of electrode work function by the deposition of alkali metal additives increases the NI surface production on the gas discharge electrodes. The persistent alkali metal coverage of gas discharge electrodes leads to the long-term highly efficient NI production of SPS. The principal mechanisms of intense surface-plasma NI production in the SPS are interrelated. The dynamic plasma particle bombardment modifies the electrode surface synergistically and the resulting surface condition determines the NI emission from the electrode in an SPS. The efficiency of negative ion production on the gas-discharge cathode and anode surfaces, as well as on the surfaces of NI emitters in plasma separated from the discharge circuit, is discussed.

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Correspondence to Yuri I. Belchenko .

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Belchenko, Y.I., Wada, M. (2023). Physics of Surface-Plasma H Ion Sources. In: Bacal, M. (eds) Physics and Applications of Hydrogen Negative Ion Sources. Springer Series on Atomic, Optical, and Plasma Physics, vol 124. Springer, Cham. https://doi.org/10.1007/978-3-031-21476-9_14

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