Isotope separators for radioactive ion beams

Short-lived nuclei used for astrophysical or nuclear reaction studies require acceleration to energies of interest. Unless the accelerator provides a selection of the isotope of interest, an isotope separator with optimal separation factor must be used to inject the ions into the accelerator. The actual separation factor can be very important because the production rates between neighboring isotopes or isobars can vary by orders of magnitude. Isotope separator concepts are presented here that have the following properties: (1) they eliminate ions scattered on residual gas atoms; (2) they eliminate ions that have undergone charge exchange within the acceleration gradient following the ion source; and (3) the geometries and fields of the system are designed to reduce image abberations so as to allow isobaric separation. These properties are realized by using two separation stages at different potentials relative to the ion source (e.g., 50 kV and 300 kV) with each stage a combination of sector and multiplet fields to achieve overall stigmatic imaging, but with astigmatic beams within the sector fields