Characteristics of low-energy intense ion beam formation and transport

Abstract

MEVVA-ion sources with a modified three-electrode ion optical system for the formation of wide aperture low-energy (100–400 V) ion beams were used to produce ion beams of different elements with a current up to 40 mA and energy up to 400 V. The peculiarities of such beam formation and transport by a wide-aperture plasma lens (PL) are investigated. Beam transport in the transport channel is shown to be improved by the PL. PL operation in the magnetic regime shows that the suppressor grid secondary electron emission beam accompanying the ion beam has a current of 30% of the total ion beam current. These electrons contribute to the charge-compensation plasma medium in the beam transport channel and in the PL. The main contribution to the compensating secondary electron production (60%–70%) is due to the ion beam but experimentally observed values of the beam floating potential appear high enough (25–50 V), and this does not exclude an influence of dynamical decompensation.