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The 14 MeV neutron emission from JET deuterium discharges is analysed on the basis of the information on all neutron diagnostics available on JET. This emission is due to the d + t → α + n reaction, mainly, the triton burn-up process, and is used to determine the fast triton confinement. A simplified model for triton burn-up neutron emission has been used and provides an adequate description of the 14 MeV emission. First orbit triton losses are found to amount to 50%, 20% and 10% at Ip = 1 MA, 2 MA and 3 MA, respectively. Neutron emission spectroscopy measurements with the magnetic proton recoil neutron spectrometer have detected a contribution to the 14 MeV emission due to residual tritium. For the selected (low impurity) discharges analysed in this paper 15% of the 14 MeV emission comes from the residual tritium reactions. It is also found that the residual tritium concentration tends to increase with increasing impurity content.

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A new control and monitoring (C&M) system is being developed for the TOFOR and MPRu fusion neutron spectrometers within the Joint European Torus enhancement program. The system, which is an evolution of the existing C&M system of the MPR spectrometer, consists of a controlled pulsed light source distributed by an optical fiber network to all photomultiplier tubes used in the plastic scintillator based spectrometers. The light source is a green Nd:LSB solid-state laser complemented by blue light emitting diode sources. Pulse height distributions for each detection channel are recorded to set the spectrometers to prescribed working points and monitor deviations. Absolute reference is obtained complementing the controlled light source with radioactive sources. In this article we report on the C&M prototype design and component tests for the MPRu spectrometer. The results show that the laser and the associated optics provide a controlled light pulse of intensity covering a dynamic range of more than four orders of magnitude. The choice of optical fiber diameters is critical for achieving the desired stability and uniformity of the light intensity collected by each MPRu detector.

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An analytical approximation of the Doppler broadening function ð; xÞ is proposed. This approximation is based on the solution of the differential equation for ð; xÞ using the methods of Frobenius and parameters variation. The analytical form derived for ð; xÞ in terms of elementary functions is very simple and precise. It can be useful for applications related to the treatment of nuclear resonances, mainly for calculations of multigroup parameters and resonances self-protection factors, the latter being used to correct microscopic cross section measurements by the activation technique.