A compact RF driven H- ion source for linac injection

A compact RF-driven H/sup -/ ion source has been developed for use as an injector for the AccSys radio frequency quadrupole linacs. A multicusp magnetic bucket geometry developed at Lawrence Berkeley Laboratory confines the plasma created by an antenna driven by 35 kW (peak) of pulsed RF power at 1.8 MHz. A three-electrode system is used to extract and accelerate the H/sup -/ beam, which is then focused into the RFQ by an einzel lens. Permanent magnets in the extraction region sweep electrons onto the second electrode at energies up to half of the full acceleration voltage. A fast pulsed valve allows the hydrogen gas supply to be pulsed, thus minimizing the average gas flow rate into the system. The design features and performance data from the prototype are discussed.<
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