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Dedicated nuclear diagnostics have been designed, developed, and built within EUROFUSION enhancement programs in the last ten years for installation at the Joint European Torus and capable of operation in high power Deuterium–Tritium (DT) plasmas. The recent DT Experiment campaign, called DTE2, has been successfully carried out in the second half of 2021 and provides a unique opportunity to evaluate the performance of the new nuclear diagnostics and for an understanding of their behavior in the record high 14 MeV neutron yields (up to 4.7 × 1018 n/s) and total number of neutrons (up to 2 × 1019 n) achieved on a tokamak. In this work, we will focus on the 14 MeV high resolution neutron spectrometers based on artificial diamonds which, for the first time, have extensively been used to measure 14 MeV DT neutron spectra with unprecedented energy resolution (Full Width at Half Maximum of ≈1% at 14 MeV). The work will describe their long-term stability and operation over the DTE2 campaign as well as their performance as neutron spectrometers in terms of achieved energy resolution and high rate capability. This important experience will be used to outline the concept of a spectroscopic neutron camera for the SPARC tokamak. The proposed neutron camera will be the first one to feature the dual capability to measure (i) the 2.5 and 14 MeV neutron emissivity profile via the conventional neutron detectors based on liquid or plastics scintillators and (ii) the 14 MeV neutron spectral emission via the use of high-resolution diamond-based spectrometers. The new opportunities opened by the spectroscopic neutron camera to measure plasma parameters will be discussed. [ABSTRACT FROM AUTHOR]

A digital pulse shape discrimination system (DPSD) has been used in conjunction with collimated NE213 scintillators for neutron spectroscopic measurements at high count rates (MHz range) in Joint European Torus discharges (DD and DT fueled, neutral beam injection and rf heated). The system, developed at ENEA-Frascati, is based on a commercial 200 MHz 12-bit analog to digital transient recorder card, which digitizes the direct output signal from the anode of a photomultiplier. Among the unique features of this DPSD system are the possibility of postexperiment data reprocessing, high count rate operation, and simultaneous neutron and gamma (γ) spectroscopy. Separation between γ and neutron (n) events is performed by means of dedicated software exploiting the charge comparison method; separate n and γ pulse height distributions are obtained and an example of neutron spectrum unfolding is shown. Implications of the DPSD in future neutron diagnostic systems on large and next step tokamaks are discussed. [ABSTRACT FROM AUTHOR]

Measurements of fluctuations in the neutron yield are made on the tokamak fusion test reactor (TFTR) with plastic scintillators. Light from the scintillators is coupled through acrylic rods or fiber-optic cables to photomultipliers operated in current mode. Discrimination against hard x rays is accomplished through comparison with the signal from a ZnS([sup 6]Li) scintillator. These measurements are useful in studies of deuterium pellet deposition, of the acceleration of beam ions during major radial compression, and of MHD instabilities. Techniques for measuring the neutral beam density profile and Q[sup equv, sub dt], using neutron fluctuation measurements during pellet injection also have been proposed. [ABSTRACT FROM AUTHOR]