Neutron detection technologies and measurement challenges at JET and ITER

In the development of nuclear fusion energy technologies based on deuterium-tritium (DT) reaction, which releases a high energy neutron around 14.1 MeV, robust and accurate neutron detection technologies are needed. These are required for monitoring and control of plasma conditions, tritium accountancy, and for the measurement of fusion power itself. The JET device, based at Culham in the UK and funded by the EU, is currently the largest operating fusion tokamak device operating worldwide, also with the capability and infrastructure to operate with fusion plasmas containing tritium. A new DT experiment is scheduled over the next few years, which presents a unique opportunity to gain further knowledge and experience in fusion technologies, including the nuclear metrology and technological aspects of neutron detection for fusion. JET operations and experience are now strongly oriented to provide input into the preparations for the ITER device, being constructed in Cadarache, France--an international endeavour comprising seven members: China, the European Union, India, Japan, Korea, Russia and the United States--and expected to be operational by the 2025. This paper gives an overview of the range of neutron detection and diagnostic systems currently employed at JET and those being designed, built and considered for ITER, including neutron spectrometers, magnetic proton recoil spectrometers, fission yield counters, diamond detectors and activation foil-based systems and other systems. We identify the key technologies and challenges for neutron detection systems in fusion environments.