A new deuterium-tritium experimental, DTE2, campaign has been conducted at the Joint European Torus (JET) between August 2021 and late December 2021. Motivated by significant enhancements in the past decade at JET, such as the ITER-like wall and enhanced auxiliary heating power, the campaign achieved a new fusion energy world record and performed a broad range of fundamental experiments to inform ITER physics scenarios and operations. New capabilities in the area of fusion product measurements by nuclear diagnostics were available as a result of a decade long enhancement program. These have been tested for the first time in DTE2 and a concise overview is provided here. Confined alpha particle measurements by gamma-ray spectroscopy were successfully demonstrated, albeit with limitations at neutron rates higher than some 1017 n/s. High resolution neutron spectroscopy measurements with the magnetic proton recoil instrument were complemented by novel data from a set of synthetic diamond detectors, which enabled studies of the supra-thermal contributions to the neutron emission. In the area of escaping fast ion diagnostics, a lost fast ion detector and a set of Faraday cups made it possible to determine information on the velocity space and poloidal distribution of the lost alpha particles for the first time. This extensive set of data provides unique information for fundamental physics studies and validation of the numerical models, which are key to inform the physics and scenarios of ITER.

The most performant deuterium-tritium (DT) plasma discharges realized by the Joint European Torus (JET) tokamak in the recent DT campaign have produced neutron yields on the order of 1018 n/s. At such high neutron yields, gamma-ray spectroscopy measurements with scintillators are challenging as events from the neutron-induced background often dominate over the signal, leading to a significant fraction of pileup events and instability of the photodetector gain along with the consequent degradation of the reconstructed spectrum. Here, we describe the solutions adopted for the tangential lanthanum bromide spectrometer installed at JET. A data acquisition system with free streaming mode digitization capabilities for the entire duration of the discharge has been used to solve dead-time related issues and a data reconstruction code with pileup recovery and photodetector gain drift restoration has been implemented for off-line analysis of the data. This work focuses on the acquired data storage and parsing, with a detailed explanation of the pileup recovery and gain drift restoration algorithms.

Nuclear fusion research is one of the most prominent fields set to revolutionize the energy market in the medium-long term period. Recent scientific achievements, such as the ones obtained at JET [1] and NIF [2], have renewed public and private interest in this topic, sparking the creation of numerous new projects and reactor concepts. Nuclear diagnostics are an essential tool to assess any deuterium-tritium machine performance. Absolute neutron counting is the gold standard technique to measure fusion power. Neutron emission spectroscopy grants access to the fuel ion physics providing information on the fuel ion temperature and energy distribution, the fuel ion ratio and the thermal to non-thermal neutron fraction. Gamma-ray and hard X-ray spectroscopy are the most direct way to obtain information on the fast particle energy distribution and their interaction with the plasma. Fusion nuclear diagnostics need to be carefully designed to operate in extreme cenarios, both in terms of operational capabilities (energy range, energy resolution, counting rate potential, etc.) and in terms of robustness in the harsh environment of a nuclear reactor. In this work, we present the state of the art for nuclear measurements in fusion experiments and we discuss possible solutions for the next-generation reactors.

The Deuterium Tritium (DT) Experiment campaign 2 (DTE2) has been successfully carried out at the Joint European Torus. An important goal of the campaign has been the detailed and systematic measurement of fusion born products, benefitting from a preparatory diagnostic upgrade program over the recent years. This talk will present an overview of the measurements, some of the unprecedented opportunities for physics studies they have opened and the challenges that still need to be addressed in preparation for ITER. Fusion products have been measured in a broad range of scenarios primarily by nuclear diagnostics and, for the first time, with an ITER like wall, which allowed testing many of the methods envisaged for the nuclear phase of ITER. High resolution gamma-ray spectroscopy has been demonstrated for the first time in a 50:50 DT plasma. 17 MeV gamma-rays born from fusion reactions between deuterium and tritium have been successfully detected and used to develop a method to determine the fusion power, complementing that based on neutron yield measurements. Slowing down, confined alpha particles with energies in excess of ?1.9 MeV were detected by means of the 4.44 MeV gamma-ray peak that comes from their spontaneous reaction with 9Be impurities. As far as neutron measurements are concerned, chemical vapour deposition diamonds have been used to measure the neutron spectrum on multiple lines of sight (LOS) and complemented more established, single LOS data obtained with the magnetic proton recoil spectrometer. The successful upgrade of the set of Faraday cups and the fast ion loss detector made it possible to detect lost alpha particles, to determine their velocity space and to study their interplay with instabilities. From a more technical viewpoint, DTE2 has also allowed testing some of the reference solutions so far adopted in the design of diagnostics for fusion products at ITER and to learn some lessons. These range from the essential role that attenuators have in enabling gamma-ray measurements, particularly LiH, to the full assessment of the background that pollutes the data for some applications.