Fusion divided: what prevented European collaboration on controlled thermonuclear fusion in 1958.

The European Organization for Nuclear Research (CERN) in Geneva, Switzerland, is renowned for operating the world's largest particle accelerator and is often regarded as a model of high-profile international collaboration. Less well known, however, is a key episode from the late 1950s, when CERN clashed with the research priorities of similar organizations. The issue centred on a CERN-sponsored study group on controlled thermonuclear fusion, which brought together scientists from CERN member states, as well as representatives from the European Atomic Energy Community (Euratom), the European Nuclear Energy Agency (ENEA) and the US Atomic Energy Commission (AEC). While their meetings succeeded in creating an international network for exchanging reports and coordinating projects to avoid duplication, the initiative failed to establish joint fusion research programmes in Europe. This article explores the reasons behind this outcome to provide insights into intergovernmental power dynamics and scientific competition and how these two factors favoured the creation of a new fusion research institution in the UK, the Culham Laboratory. In doing so, the article contributes to a deeper understanding of the role of science in European integration, while also highlighting that CERN's involvement in application-oriented research remains an underexplored aspect of its history.