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A gas-fed negative ion source for use in an accelerator mass spectrometry system has been built at the United States Naval Research Laboratory. This ion source is a filament driven plasma ion source using a multicusp magnet arrangement for plasma confinement. Our specific design was assisted by modeling using the SIMION code to optimize beam extraction optics. In addition to the ion source modeling, preliminary characterization of the plasma behavior was performed, which showed the typical and expected order of magnitude increase in collected plasma current when a multicusp magnetic arrangement is employed versus the case with no magnets. Future work will involve implementing a Langmuir probe for more detailed characterization of the plasma, investigation of the effects of using a symmetric rather than a multicusp magnet arrangement, and ultimately the extraction and characterization of ion beams from the source. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Our previous work experimentally demonstrated the enhancement of electrochemical hydrogen insertion into palladium by modifying the chemical composition of the cathode surface with Pb, Pt and Bi, referred to as surface promoters. The experiment demonstrated that an optimal combination of the surface promoters led to an increase in hydrogen fugacity of more than three orders of magnitude, while maintaining the same current density. This manuscript discusses the application of Density Functional Theory (DFT) to elucidate the thermodynamics and kinetics of observed enhancement of electrochemical hydrogen insertion into palladium. We present theoretical simulations that: (1) establish the elevation of hydrogen’s chemical potential on Pb and Bi surfaces to enhance hydrogen insertion, (2) confirm the increase of a Tafel activation barrier that results in a decrease of the reaction rate at the given hydrogen overpotential, and (3) explain why the surface promoter’s coverage needs to be non-uniform, namely to allow hydrogen insertion into palladium bulk while simultaneously locking hydrogen below the surface (the corking effect). The discussed DFT-based method can be used for efficient scanning of different material configurations to design a highly effective hydrogen storage system. [ABSTRACT FROM AUTHOR]