Negative-hydrogen-ion sources

There are two main areas of negative hydrogen ion applications: injection into high energy accelerators and production of beams of energetic hydrogen atoms for fusion devices. In both cases, the ease with which the charge state of negative ions can be changed by either single or double electron stripping is the reason that made their application attractive. In tandem accelerators, the final energy of H+ ions is twice as high as it would correspond to the terminal voltage, in circular accelerators (synchrotrons, storage rings) injection of H+ ions by full stripping of H- ions in a foil inside the ring is not limited by the Liouville's theorem and results in a higher phase space density than achieved by direct H+ injection. Finally, beams of hydrogen atoms at energies above 100 keV, which will be required for plasma heating and current drive in future fusion devices, can efficiently be produced only by acceleration of negative ions and their subsequent neutralization