Negative-hydrogen-ion production from a nanoporous 12CaO•7Al2O3 electride surface

A high production rate of negative hydrogen ions (H-) was observed from a nanoporous 12CaO center dot 7Al(2)O(3) (C12A7) electride surface immersed in hydrogen/deuterium low-pressure plasmas. The target was negatively biased at 20-130V, and the target surface was bombarded by H-3(+) ions from the plasma. The production rate was compared with that from a clean molybdenum surface. Using the pseudo-exponential work-function dependence of the H- production rate, the total H- yield from the C12A7 electride surface bombarded at 80V was evaluated to be 25% of that from a cesiated molybdenum surface with the lowest work-function. The measured H- energy spectrum indicates that the major production mechanism is desorption by sputtering. This material has potential to be used as a production surface of cesium-free negative ion sources for accelerators, heating beams in nuclear fusion, and surface modification for industrial applications. (C) 2018 The Japan Society of Applied Physics