Hydrogen/helium ion injector for accelerator-based microprobe facilities

The hydrogen/helium ion injector comprising a newly designed helicon RF ion source with higher brightness (∼100 A/(m2 rad2 eV) for helium and ∼50 A/(m2 rad2 eV) for hydrogen) and, a compact mass separator has been designed for use in microprobe facilities. The effects of magnetic traps and plasma resonances were employed for increasing of the RF source brightness. To operate the helicon RF ion source with hydrogen/helium plasma a magnetic system with circular permanent magnets was designed and constructed, permitting a generation of a longitudinal magnetic field Bz ∼ 100 G along the length of the RF antenna and of a longitudinal magnetic field ∼1000 G with effective field length of about 10 cm to confine and transfer the plasma to the extraction system. This ion source has been operated with current densities of 1-30 mA/cm2 and an RF power input into the plasma of 20-150 W. By the source outlet aperture a central part of the beam with the maximum beam phase density for phase volume of 1-100 mm2 mrad2 was used. The phase set degradation due to aberration in the injector ion-optic system was simulated with allowance for multipole field components and fringe field effect.