Separation of isobars with a gas-filled magnet

When an ion passes through a magnetic field region filled with gas, its trajectory is governed by the magnetic deflection and by atomic collisions which change its charge state by capture and loss of electrons. Under appropriate conditions, the average trajectories of isobaric ions will be distinct because they have different mean charge states in the gas, and physical separation of the ions becomes possible. A systematic study of this method has been performed with a split-pole magnetic spectrograph at Argonne National Laboratory. The application of the method to the separation of isobars in AMS measurements of various radioisotopes is described. The gas-filled magnet acts also as a powerful separator for ions with different mass but equal mass-to-charge ratio which are simultaneously accelerated in linear accelerators.