Scintillators and Cherenkov detectors for the registration of 10.8 MeV gamma rays

© Published under licence by IOP Publishing Ltd. The identification of nitrogen by neutron activation has been utilized in both explosive detection and in-vivo metabolic analysis. The 10.8 MeV gamma ray line emitted by thermal neutron capture provides a unique signature, however, due to its high energy its registration is non-trivial. Conventional approaches have used large dense inorganic scintillators which inevitably entail considerable expense. We examine the capabilities of arrays of smaller scintillation detectors and the use of glass Cherenkov detectors as an alternative

Preanalysis of Neutron Activation Measurements in Shielding Penetrations at JET

In the present work, the preanalysis of activation foil experiments to determine neutron fluence rates along JET hall ducts and labyrinths is discussed. Simulations were performed using computational codes MCNPX and FISPACT-II and a detailed model of the JET hall, including the tokamak, biological shield and penetrations. The induced activity and detector count rate were predicted for activation foils placed at selected positions within the JET hall for Deuterium-Deuterium and Deuterium-Tritium JET plasma sources. The results of the calculations showed that satisfactory counting statistics can be obtained with the use of activation detectors and therefore activation analysis offers an unbiased and robust cross-benchmarking tool for comparison against other experimental and computation techniques applied in neutron streaming studies at JET

calibration of activation foils at the 14 mev frascati neutron generator

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preparation of activation experiments for iter material characterization and data validation in the deuterium tritium jet campaign

The levels of induced activity in samples of ITER materials and dosimetry foils to be irradiated during the planned JET campaign with deuterium-tritium (D-T) plasma were predicted. Calculations were performed for the neutron energy spectrum of the JET internal Long Term Irradiation Station (LTIS). The European Activation System (EASY-II) and the EAF-2010 nuclear data library were used in order to estimate specific activity and dose rates as a function of time after the end of irradiation. The results of the study provide important data for comparison against activation measurements and support the planning of the irradiation, measurement and radiation protection procedures to be implemented in the planned JET activation experiment

ITER oriented neutronics benchmark experiments on neutron streaming and shutdown dose rate at JET

Neutronics benchmark experiments are conducted at JET in the frame of WPJET3 NEXP within EUROfusion Consortium for validating the neutronics codes and tools used in ITER nuclear analyses to predict quantities such as the neutron flux along streaming paths and dose rates at the shutdown due to activated components. The preparation of neutron streaming and shutdown dose rate experiments for the future Deuterium-Tritium operations (DTE2 campaign) are in progress. This paper summarizes the status of measurements and analyses in progress in the current Deuterium–Deuterium (DD) campaign and the efforts in preparation for DTE2

On the mechanisms governing gas penetration into a tokamak plasma during a massive gas injection

A new 1D radial fluid code, IMAGINE, is used to simulate the penetration of gas into a tokamak plasma during a massive gas injection (MGI). The main result is that the gas is in general strongly braked as it reaches the plasma, due to mechanisms related to charge exchange and (to a smaller extent) recombination. As a result, only a fraction of the gas penetrates into the plasma. Also, a shock wave is created in the gas which propagates away from the plasma, braking and compressing the incoming gas. Simulation results are quantitatively consistent, at least in terms of orders of magnitude, with experimental data for a D 2 MGI into a JET Ohmic plasma. Simulations of MGI into the background plasma surrounding a runaway electron beam show that if the background electron density is too high, the gas may not penetrate, suggesting a possible explanation for the recent results of Reux et al in JET (2015 Nucl. Fusion 55 093013)

Modelling of the effect of ELMs on fuel retention at the bulk W divertor of JET

Effect of ELMs on fuel retention at the bulk W target of JET ITER-Like Wall was studied with multi-scale calculations. Plasma input parameters were taken from ELMy H-mode plasma experiment. The energetic intra-ELM fuel particles get implanted and create near-surface defects up to depths of few tens of nm, which act as the main fuel trapping sites during ELMs. Clustering of implantation-induced vacancies were found to take place. The incoming flux of inter-ELM plasma particles increases the different filling levels of trapped fuel in defects. The temperature increase of the W target during the pulse increases the fuel detrapping rate. The inter-ELM fuel particle flux refills the partially emptied trapping sites and fills new sites. This leads to a competing effect on the retention and release rates of the implanted particles. At high temperatures the main retention appeared in larger vacancy clusters due to increased clustering rate