Intense, high brightness H- beams from surface plasma sources

High-current H- beams from a reliable surface plasma source are of great interests for spallation neutron sources and hadron colliders. At Maryland, H- beams have been studied using a magnetron and a Penning-type surface plasma source. Stable operating conditions with negligible beam noise have been achieved in both cases. The beam characteristics are much improved in the Penning geometry; the beam brightness is about an order of magnitude higher. An emission current density of similar to 1A/cm(2) with normalized beam brightness of greater than or similar to 10(12)A/(m-rad)(2) has been achieved. The minimum energy spread Delta E (FWHM) is measured less than or similar to 2.5eV. The actual Delta E is possibly much smaller since this value is close to the resolution of the energy analyzer. The results are sensitive to the beam noise, and the gas pulse is the key control parameter here. Long, stable operations with very limited source maintenance have been noted. So far, an emission aperture of diameter = 0.6mm is used when the H- beam current is greater than or similar to 2mA at 10kV. The beam current can be scaled to greater than or similar to 30mA for an emission aperture of diameter similar to 2.4mm. The critical issues for noiseless, high-brightness H- beams, the source performance, and the scaling of beam parameters are discussed.