Ion-collection characteristics of photoplasma for atomic vapor laser isotope separator module in electrostatic fields

Abstract

The laser-based isotope separation process is currently pursued to enrich precursor medical isotopes like lutetium-176 and ytterbium-176. India has successfully produced radionuclide lutetium-177 for clinical use by neutron activation. Atomic vapor laser isotope separation (AVLIS) is used as the enrichment technology. Understanding the physics and technology of processes, like atomic-beam generation, photoplasma production, and ion collection, is essential to designing any AVLIS module. So, a stand-alone research facility was developed before the production plant. This article describes the facility and the experimental and theoretical studies of ion collection in electrostatic fields using barium as the working element. Two types of ion extractors, plate–photoplasma–plate and plate–photoplasma–grid–plate, were designed and fabricated. A model of photo-ion collection in these electrostatic ion extractors was arrived at. Scaling of the initial photo-ion densities and the electric fields is crucial to photoplasma evolution spanning single-particle to collective regimes. Estimates of ion-collection rates of the Indian AVLIS modules for lutetium-176 and ytterbium-176 were carried out. By invoking plasma physics, the technological aspect of producing enriched isotopes was solved by judiciously integrating the atom source, laser system, photoplasma, and ion-extractor geometries. Limitations of the electrostatic ion extractors were also flagged.