Extending the Energy Range of a 7 MV Van de Graaff Using Triply-Charged Beams: Applications to Neon and Argon Ions

With only minor modifications, an RF ion source has been used to produce copious beams of triply-charged ions of neon and argon, thus extending the useful energy range of a CN model Van de Graaff to 21 MeV. Absolute beam current measurements show that beams of ~500 nA can be routinely obtained. Application of these has been made to beam-foil spectroscopy experiments, which also serve to positively identify the beams. The beam intensity is most sensitive to the diameter of the exit canal. It is also necessary to be able to monitor current drawn by the RF oscillator. A pre-selecting magnet filters undesired charge states prior to acceleration.