A DC PROTON INJECTOR FOR USE IN HIGH-CURRENT CW LINACS

A 75-keV dc and pulsed-mode proton injector is being developed for beam testing of a 100-mA, 6.7-MeV cw radio frequency quadrupole (RFQ) at Los Alamos. A microwave proton source operating at 2.45 GHz produces 130-mA hydrogen-ion beam currents with>85 % proton fraction, yielding the 110-mA proton current required at the RFQ injection point. Doppler-shift spectroscopy confirms previously measured proton fractions. The discharge may be pulsed by current modulation of the magnetron power supply. A 1-MHz coherent oscillation observed in the extracted ion beam was eliminated by selecting proper magnetron operation. Transport and matching of the proton beam to the RFQ is accomplished by a two-solenoid, beam space-charge neutralized low-energy beam transport (LEBT) system. The injector was temporarily reconfigured to operate at 50 keV for injector matching studies into a 1.25 MeV cw RFQ. A maximum current of 100-mA has been accelerated through the RFQ in cw mode.