Design and Analytical Evaluation of a New Ion Collection Geometry for Improvement in Quantity and Quality of Product During Laser Isotope Separation

Isotopes of some metals are used in medical applications like diagnosis/treatment of cancer, arthritis and other illnesses, and in nuclear reactors for neutron shielding. Although atomic vapor laser isotope separation (AVLIS) route for separation of these isotopes is preferred, production of desired isotope at high quantity and quality (enrichment) is a challenge. Generally, in the AVLIS process, for efficient collection of ions produced by laser, the collector plate is kept at high voltage of about -3 kV. So, the collected ions hit the plates at a kinetic energy of ~3 keV and, in turn, sputter out the previously deposited atoms (sputtering yield is ~2-3). So, the maximum quantity of the product that can be produced by the process is only a few layers of atoms on the plate. In addition, since the ion collector plate is kept close to the plasma for generating sufficient electric field for extraction of ions, the plate collects some undesired isotopes scattered from the vapor stream diluting the enrichment of the product. To avoid these problems of sputtering by collected ions (limiting quantity of product) and scattering of undesired atoms onto the plate (limiting quality), we design a new ion collection geometry using a combination of the grid and plate structure. We derive analytical expressions to theoretically evaluate the performance of our ion collection geometry and compare it with the performance of conventional geometry. Both quantity and quality of the product in our design are found to be significantly better than that of the conventional method.