The Cyclotron Hall of Louvain-la-Neuve, Birthplace of Postaccelerated Radioactive Ion Beams for Nuclear and Astrophysics Research

Abstract

The European Physical Society (EPS), upon nomination by the Belgian Physical Society, has decided to confer a Historic Site Award to the Cyclotron Hall in Louvain-la-Neuve (Figure 1). This place hosted in 1990 a worldleading nuclear-astrophysics experiment involving for the first time the post-acceleration of a short-lived radioactive element and the successful study of a key nuclear reaction in the stars. This world premiere was the result of an intensive collaboration between research teams from three Belgian universities: ULB, KU Leuven and UCLouvain. There are only two other EPS historic sites in Belgium (EPS Historic Sites European Physical Society (EPS): the Hotel Metropole in Brussels (‘In 1911, the Hotel was the venue of the Solvay Council, dedicated to what soon would be called “The Theory of Radiation & Quanta”’) and the Heilige-Geest college in Leuven (“Georges Lemaître, original founder of the theory of the Big Bang, developed in this college his ideas about an expanding universe consistent with theory and observations”). To celebrate this event, a commemorative plate was unveiled on Tuesday, 12 October 2021, at the “de Hemptinne” building of UCLouvain, which hosts the Cyclotron Hall (Figure 1). The commemorative plate holds the following text: This building has hosted a worldleading nuclear-physics experiment involving the post-acceleration of shortlived radioactive nuclides. A beam of N, an unstable isotope of nitrogen with a half-life of 10 minutes, was produced for the first time on 21 June 1989 by coupling two cyclotrons with an on-line ion source. In December 1990, the energy, intensity, and purity of the beam allowed the successful study of the key stellar reaction within the hot Carbon-NitrogenOxygen (CNO) cycle: N + H -> 14 O + γ. The technologies and instrumentation developed to produce and use energetic radioactive ion beams, and the evidence that it was then possible to perform detailed nuclear-reaction studies with short-lived radioactive isotopes, has given rise to the birth of new research fields in nuclear physics and astrophysics. This breakthrough in accelerator, nuclear-physics and nuclear-astrophysics research was the result of an intensive collaboration between teams from the Belgian universities ULB, KU Leuven and UCLouvain. It paved the way for a multitude of challenging experiments with radioactive ion beams involving major European collaborations and has led to the construction of significant facilities for producing radioactive ion beams in many countries around the world. Since then, the field of radioactive ion beams, produced with the postaccelerated isotope separator on-line technique or with the complementary in-flight technique, has blossomed all over the world, giving rise to the new Radioactive Nuclear Beams (RNB) conference series, of which the second one took place in 1991 in Louvain-la-Neuve soon after the pioneering experiment. The “Euroschool on Exotic Beams,” dedicated to training of Ph.D. students and young researchers in radioactive beams science, was initiated in 1993 and until 2000 hosted at KU Leuven. From then on it traveled throughout Europe and in 2017 it came back to Leuven, to celebrate the 25th school. In 2011, the first Advances in Radioactive Isotope Science conference was organized in Leuven as a merger of the Exotic Nuclei and Atomic Masses and RNB conferences and is now the flagship conference of the field.