The principles and operation at Joint European Torus (JET) of the first magnetic proton recoil (MPR) spectrometer for measurement of fusion neutron spectra are described. Some technical aspects of the instrument are discussed, including energy calibration and monitoring system. Data from the recent experimental campaign with tritium at JET are presented as examples of the MPR’s diagnostic abilities. It is shown that the spectrometer is a flexible and versatile instrument, capable of delivering high-quality data on a number of plasma parameters. In particular, the observation of the so-called α knock-on effect in neutron emission spectroscopy is discussed.

The energy spectrum of the d+t→α+n neutron emission has been measured in experiments carried out at JET for plasmas of deuterium–tritium subjected to minority ion cyclotron resonance heating (ICRH) tuned to deuterium. The data obtained with the magnetic proton recoil spectrometer were of sufficient quality to distinguish up to three spectral components of neutron emission some of which were time resolved. A new analysis model was used to derive information on the underlying deuteron velocity distributions and their corresponding energy densities in the plasma. This experiment represents the first use of neutron emission spectroscopy for detailed diagnosis of the response of fusion plasmas to the applied ICRH power for different plasma conditions, including the time evolution over the heating pulse duration for individual discharges. In particular, ICRH effects on the plasma, together with the power absorption mechanisms, were studied as a function of the minority ion concentration in the range 9–20%.

Abstract. The status of the Joint Evaluated Fission and Fusion file (JEFF) is described. JEFF-3.1 comprises a significant update of actinide evaluations, materials evaluations that have emerged from various European nuclear data projects, the activation library JEFF-3.1/A, the decay data and fission yield sub-libraries, and fusion-related data files from the EFF project. The revisions were motivated by the availability of new measurements, modelling capabilities and trends from integral experiments. Validations have been performed, mainly for criticality, reactivity temperature coefficients, fuel inventory and shielding of thermal and fast systems. Compared with earlier releases, JEFF-3.1 provides improved performance with respect to a variety of scientific and industrial applications. Following on from the public release of JEFF-3.1, the French nuclear power industry has selected this suite of nuclear applications libraries for inclusion in their production codes.

The diagnostics functions of neutron measurements as well as the roles played by neutron yield monitors, cameras and spectrometers are reviewed. The importance of recent developments in neutron emission spectroscopy (NES) diagnostics is emphasized. Results are presented from the NES diagnosis of the Joint European Torus (JET) plasmas performed with the magnetic proton recoil (MPR) spectrometer during the first deuterium tritium experiment of 1997 and the recent trace tritium experiment of 2003. The NES diagnostic capabilities at JET are presently being enhanced by an upgrade of the MPR (MPRu) and a new 2.5 MeV time-of-flight (TOF) neutron spectrometer (TOFOR). The principles of MPRu and TOFOR are described and illustrated with the diagnostic role they will play in the high performance fusion experiments in the forward programme of JET largely aimed at supporting the International Thermonuclear Experimental Reactor (ITER). The importance of the JET NES effort for ITER is discussed.

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