High-current D− production by charge exchange in sodium

Abstract

A beam of D− ions has been produced at 7–13 keV, with currents up to 2.2 A, using charge exchange in sodium vapor. The beam profile is bi-Gaussian with angular divergence 0.7°×2.8° and peak current density 15 mA/cm2. The characteristics of the beam are in excellent agreement with predictions based on atomic cross sections. The sodium vapor target is formed by a jet directed across the beam. The sodium density drops rapidly in the beamline downstream from the charge exchange region, decreasing three orders of magnitude in 15 cm. Measurement and analysis of the plasma accompanying the beam demonstrate that plasma densities nearly equal to the beam density are obtained 1 m from the charge exchange medium. The plasma produced in the sodium is thus well confined to the charge exchange region and does not propagate along the beam.