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The Resonance Ionization Laser Ion Source (RILIS) has become an essential feature of many radioactive ion beam facilities worldwide since it offers an unmatched combination of efficiency and selectivity in the production of ion beams of many different chemical elements. In 2019, the laser ion source setup MELISSA is going to be established at the CERN-MEDICIS facility, based on the experience of the workgroup LARISSA of the University Mainz and CERN ISOLDE RILIS team. The purpose is to enhance the capability of the radioactive ion beam supply for end users by optimizing the yield and the purity of the final product. In this article, the blueprint of the laser ion source, as well as the key aspects of its development and operation are presented.

Resonance ionization mass spectroscopy has proven to be a very efficient and selective method for the spatially resolved ultratrace determination of actinide contaminations, and the analysis of specific element and isotopic distributions on surfaces and environment particles. We report on the identification of highly element-selective optical excitation schemes identified for this purpose, with a particular focus on the precise determination of the isobaric ratios of 235U to 239Pu as well as 243Am to 241Pu. The chosen two-step ionization schemes were characterized with respect to their element selectivity on synthetic multi-element actinide mixtures, with an element ratio Pu : Am : U of 1 : 10 : 104, a composition which is typical, e.g., for spent nuclear reactor fuels.

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The CERN-MEDICIS facility aims to produce emerging medical radionuclides for the theranostics approach in nuclear medicine with mass separation of ion beams. To enhance the radioisotope yield and purity of collected samples, the resonance ionization laser ion source MELISSA was constructed, and provided the first laser ions at the facility in 2019. Several operational tests were accomplished to investigate its performance in preparation for the upcoming production of terbium radioisotopes, which are of particular interest for medical applications.