Efficient Production of Multiply Charged Positive Ions by Low Energy Stripping in Helium Gas

Abstract

``Low energy'' as used in this report means ionic and atomic beam velocities from approximately 5×10⁷ to 2×10⁸ cm/sec. In this velocity region an ion beam brought to charge equilibrium in helium gas has a much greater content of components of high positive charge than does the same beam charge equilibrated in other gases. To achieve this effect, however, the pressure of helium gas in a charge stripper or converter cell placed in the beam path must be much higher than in other gases. The predicted effect, calculated from the charge changing cross sections, is verified by experiments on the stripping of Li⁺ to Li⁺⁺ in air and helium. In a qualitative experiment the proton beam of the Chicago synchrocyclotron was increased 100% by equilibrating the hydrogen constituent in a 90–10 HeH² mixture before issuing it from the ion source into the acceleration chamber.