Proton injector operational results on a high-power continuous-wave radio-frequency quadrupole accelerator

A 50 keV proton injector utilizing a dc microwave source has been used to o perate a 1.25 MeV continuous wave (cw) radio-frequency quadrupole (RFQ) acc elerator. RFQ injection places stringent requirements on beam properties in cluding centroid control, emittance, and phase-space matching. The ion sour ce chosen for these applications is based on a microwave discharge operatin g at 2.45 GHz with an on-axis magnetic field near 875 G. The injector emplo ys a space-charge-neutralized, two-solenoid-lens, low-energy beam transport (LEBT) system. Proton injector development with a 1.25 MeV RFQ has resulte d in meeting the RFQ 75 mA design current specification in cw mode. Details of the ion source and LEBT operation are presented, and simulations for io n beam extraction and transport are compared with the injector measurements . The proton injector has been converted to 75 keV beam operation for injec ting into a 6.7 MeV cw RFQ. (C) 2000 American Institute of Physics. [S0034- 6748(00)62402-4].