Heavy ion separation with a gas-filled magnetic spectrograph

Heavy ions passing through a magnetic field region filled with gas experience atomic charge-changing collisions and follow trajectories approximately determined by the mean charge state in the gas. The Properties of a gas-filled Engemagneticspectrograph ate studied in detail by measuring focal:plane position spectra of fast heavy ions and their evolution as a function, of gas pressure. The method allows physical separation of pairs of isobaric ions in the focal plane. Applications in accelerator mass spectrometry experiments are described. At intermediate low pressures, single atomic charge-changing processes can be identified. A Monte Carlo simulation program of the ion transport through the gas-filled magnet is developed and reproduces closely the experimental behavior. Magnetic spectrographs have been widely utilized for the detection and identification of light and heavy ions. The magnetic rigidity, given by the momentum of . the ion divided by its .electricchal"ge, governs thetmjee­ tory of the ion in a magnetic field region and is nor­ mally a constant throughout the path of the ion in vacuum. The dispersion for ions with different magnetic rigidities results in a spatial distribution in the focal plane of the apparatus, which can be measured often with high resolution. Together with other parameters like energy or velocity, it can be used for the identifica­ tion of the ion. The situation is complicated for heavy ions by the fact that, after passage through matter (e.g. target, absorber, foil window), the ions emerge with a distribution of ionic charge states; these ions follow different trajectories in the magnetic field, as de­ termined by their charge state. On the other hand, for ions with the same mass numbers (isobaric nuclei),