Overview of JET Restart: Integrated Commissioning and Plasma Commissioning

Abstract The Joint European Torus (JET) Restart is a critical phase in the operation of the JET, enabling the transition of JET plant from Shutdown to experimental plasma campaigns. This paper provides a comprehensive overview divided into its two main stages. The first stage, Integrated Commissioning, encompasses the activation and synchronization of critical systems, from magnet energization to diagnostics calibration. The second stage, Plasma Commissioning, focuses on achieving reliable and sustained plasma initiation, conditioning plasma-facing components, and optimizing auxiliary heating and other systems. The paper details the sequential phases and steps of JET Restart, outlines the planning and coordination, and introduces how the commissioning procedures for Restart activities are reviewed, managed, and monitored. The paper also explores the specific commissioning activities required for deuterium–tritium experimental campaigns, highlighting the additional safety measures and operational adjustments needed for tritium handling. By documenting the JET Restart methodology and lessons learned, this paper provides valuable insights for the commissioning of next-generation fusion machines. As one of the most complex fusion facilities globally, JET’s Restart activities serve as a critical benchmark for the operational procedures of future large-scale fusion machines.