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In particular circumstances, nonlinear systems can collapse suddenly and abruptly. Anomalous detection is therefore an important task. Unfortunately, many phenomena occurring in complex systems out of equilibrium, such as disruptions in tokamak thermonuclear plasmas, cannot be modelled from first principles in real time compatible form and therefore data driven, machine learning techniques are often deployed. A typical issue, for training these tools, is the choice of the most adequate examples. Determining the intervals, in which the anomalous behaviours manifest themselves, is consequently a challenging but essential objective. In this paper a series of methods are deployed to determine when the plasma dynamics of the tokamak configuration varies, indicating the onset of drifts towards a form of collapse called disruption. The techniques rely on changes in various quantities derived from the time series of the main signals: from the embedding dimensions to the properties of recurrence plots and to indicators of transition to chaotic dynamics. The methods, being mathematically completely independent, provide quite robust indications about the intervals, in which the various signals manifest a predisruptive behaviour. Consequently, the signal samples, to be used for supervised machine learning predictors, can be defined precisely, on the basis of the plasma dynamics. This information can improve significantly not only the performance of machine learning classifiers but also the physical understanding of the phenomenon. more...

Tomography is applied daily to bolometric data in magnetically controlled nuclear fusion devices to infer important quantities of the studied plasmas, such as the emissivity profiles or the radiated power in different locations of the main chamber. Tomographic reconstructions are also crucial for power balance analysis and to estimate heat fluxes for turbulence studies. One of the issues, associated with any tomographic technique, resides in the ill-posed nature of the mathematical problem, meaning that more than one possible emissivity profile is compatible with the measurements within the estimated uncertainties. Therefore, a careful evaluation of the quality of the obtained reconstructions is an important step of the analysis. On Joint European Torus (JET), since the two cameras are located in different toroidal locations, axial symmetry of the plasma radiation must be assumed to perform traditional tomographic reconstructions. Such a specific hypothesis, however, cannot be guaranteed in the case of symmetry-breaking mechanisms, such as strong local gas puffing for fuelling. The present contribution addresses this problem of local plasma fuelling, focusing on the observed significant mismatch between measured and back-calculated projections in specific pulses, including the last JET DT campaign (DTE2) carried out in 2021. The analysis indicates that the observed discrepancy, due to the gas injected primarily from valves located in the same octant where one of the bolometer arrays is located, can be rectified acceptably well by a physically-based correction. The sensible improvements in the bolometric maximum likelihood tomography’s outputs are also documented, and the possible physical explanation for such a phenomenon is discussed. The study performed in this article is expected to have a significant impact on the analysis of JET data and on the physical interpretation of the results obtained during the recent DTE2 experiments, for which a proper evaluation of the radiated power estimates is of non-negligible relevance. more...

In many areas of research, from neurobiology to nuclear fusion, which investigate complex dynamical systems involving numerous, different and interconnected physical quantities, the application of advanced analysis tools based on Chaos theory and Information theory has provided significant improvements both by supporting theoretical models and by highlighting hidden relationships between quantities characterizing the observed phenomena. The present article is therefore devoted to the analysis of synchronization experiments in magnetically controlled plasmas at JET, involving a ‘target’ quantity (sawteeth) and a ‘driver’ (modulated injected radio frequency) one. The typical approach to such analysis would start from assuming that the coupling between driver and target is free from external influences. However, since sawteeth can occur naturally and constitute a confounding factor in the analysis, by relaxing such an assumption a more realistic description of the system can emerge. The use of the conditional joint recurrence plots, complemented by the conditional transfer entropy, has provided further evidences supporting the effective influence of the pacing on the fast ions populations of both the minority and of the main plasma species in H-mode plasmas. The results highlight specific physical factors affecting the efficiency of the pacing and are in agreement with modelling estimates. The analysis performed then paves the way for future studies on more recent DT pulses performed at JET, and on data from other synchronization experiments. more...

Bolometric tomography is a widely applied technique to infer important indirect quantities in magnetically confined plasmas, such as the total radiated power. However, being an inverse and ill-posed problem, the tomographic algorithms have to be carefully steered to converge on the most appropriate solutions, and often specialists have to balance the quality of the obtained reconstructions between the core and the edge of the plasma. Given the topology of the emission and the layout of the diagnostics in practically all devices, the tomographic inversions of bolometry are often affected by artefacts, which can influence derived quantities and specific studies based on the reproduced tomograms, such as power balance studies and the benchmarking of gyrokinetic simulations. This article deals with the introduction of a simple, but very efficient methodology. It is based on constraining the solution of the tomographic inversions by using a specific estimate of the initial solution, built with the data from specific combinations of detectors (called ‘masks’). It has been tested with phantom and with real data, using the Maximum Likelihood approach at JET. Results show how the obtained tomograms improve sensibly both in the core and at the edge of the device, when compared with those obtained without the use of masks as the initial guess. The correction for the main artefacts can have a significant impact on the interpretation of both the core (electron transport, alpha heating) and the edge physics (detachment, SOL). The method is completely general and can be applied by any iterative algorithm starting from an initial guess for the emission profile to be reconstructed. more...

The design of a superconducting magnet system of a fusion reactor candidate is usually based on the Cable in Conduit Conductor (CICC) concept. CICC consist of complex structures with several hundreds of highly packed, multistage twisted superconductor and copper strands, cooling structures – all wrapped in thin steel foils and jacketed in relatively thick stainless-steel pipes. As recently demonstrated, such complex morphology can be captured by fully 3D X-ray tomography. One of the three alternative winding pack (WP) options for the toroidal field coils of the European DEMO superconducting magnet system as proposed by the Italian ENEA, features a layer-wound WP design adopting a wind-and-react conductor with high aspect ratio rectangular cross section. A multi-physics modelling requiring high accuracy from the strand to the full-size conductor scale was tested on two X-ray tomography systems. For the microstructural integrity analysis of the internal tin one mm diameter Nb3Sn strand, manufactured by Western Superconducting Technologies, a microtomograph with ˜1 μm feature recognition was used. For the full-size conductor (66 x 25 mm2 internal dimensions) a high energy (> 300 kVp) microtomograph with voxel resolution of ˜20 μm was employed. Voids and/or geometrical imperfections were detected, accurately pin-pointed and locally investigated at high resolution before and after heat treatment. Dimensional measurements on the 3D internal structure of the strand showed the small dimensional changes of the strand after the heat treatment. A significant result was the determination of the twist-pitch factor in a purely non-invasive way. The 3D reconstructions of the CICC cables were used to verify the cabling and compaction processes as well as the structural integrity of the strands, wrapping foils and spiral cooling structures. Also, 3D reconstruction of strand trajectories provided a strong input for a multiphysical modelling/interpretation of mechanical–electrical properties of CICC in cryogenic–electromagnetic environments. more...

An integrated modelling methodology for the calculation of realistic plasma neutron sources for the JET tokamak has been developed. The computational chain comprises TRANSP plasma transport and DRESS neutron spectrum calculations, and their coupling to the MCNP neutron transport code, bridging plasma physics and neutronics. In the paper we apply the developed methodology to the analysis of neutron emission properties of deuterium and helium plasmas at JET, and validate individual modelling steps against neutron diagnostic measurements. Two types of JET discharges are modelled-baseline-like and three-ion radio-frequency scenarios-due to their diversity in plasma heating, characteristics of the induced fast ion population, and the imprint of these on neutron emission properties. The neutron emission modelling results are quantitatively compared to the total neutron yield from fission chambers, neutron emissivity profiles from the neutron camera, neutron spectra from the time-of-flight spectrometer, and neutron activation measurements. The agreement between measured and calculated quantities is found to be satisfactory for all four diagnostic systems within the estimated experimental and computational uncertainties. Additionally, the effect of neutrons not originating from the dominating D(D, n)He-3 reactions is studied through modelling of triton burnup DT neutrons, and, in mixed D-He-3 plasmas, neutrons produced in the Be-9(D, n gamma)B-10 reaction on impurities. It is found that these reactions can contribute up to several percent to the total neutron yield and dominate the neutron activation of samples. The effect of MeV-range fast ions on the neutron activation of In-115 and Al-27 samples is measured and computationally validated. more...

Alfvén eigenmodes (AEs) driven by energetic alpha particles can lead to enhanced fast ion transport and losses, thereby degrading the plasma performance in ITER and future magnetic confinement fusion reactors. Unexpectedly, AEs with negative toroidal mode numbers, which are currently not considered for ITER, were observed in dedicated experiments with fusion-born alpha particles on the tokamak Joint European Torus (JET). The paper provides evidence for a complex interplay between fast ions, monster sawtooth crashes and AEs. Our results highlight the need for an improved description of the synergies between different fast ion phenomena in future burning plasmas. more...

This paper summarizes the physical principles behind the novel three-ion scenarios using radio frequency waves in the ion cyclotron range of frequencies (ICRF). We discuss how to transform mode conversion electron heating into a new flexible ICRF technique for ion cyclotron heating and fast-ion generation in multi-ion species plasmas. The theoretical section provides practical recipes for selecting the plasma composition to realize three-ion ICRF scenarios, including two equivalent possibilities for the choice of resonant absorbers that have been identified. The theoretical findings have been convincingly confirmed by the proof-of-principle experiments in mixed H?D plasmas on the Alcator C-Mod and JET tokamaks, using thermal 3He and fast D ions from neutral beam injection as resonant absorbers. Since 2018, significant progress has been made on the ASDEX Upgrade and JET tokamaks in H?4He and H?D plasmas, guided by the ITER needs. Furthermore, the scenario was also successfully applied in JET D?3He plasmas as a technique to generate fusion-born alpha particles and study effects of fast ions on plasma confinement under ITER-relevant plasma heating conditions. Tuned for the central deposition of ICRF power in a small region in the plasma core of large devices such as JET, three-ion ICRF scenarios are efficient in generating large populations of passing fast ions and modifying the q-profile. Recent experimental and modeling developments have expanded the use of three-ion scenarios from dedicated ICRF studies to a flexible tool with a broad range of different applications in fusion research. AB - This paper summarizes the physical principles behind the novel three-ion scenarios using radio frequency waves in the ion cyclotron range of frequencies (ICRF). We discuss how to transform mode conversion electron heating into a new flexible ICRF technique for ion cyclotron heating and fast-ion generation in multi-ion species plasmas. The theoretical section provides practical recipes for selecting the plasma composition to realize three-ion ICRF scenarios, including two equivalent possibilities for the choice of resonant absorbers that have been identified. The theoretical findings have been convincingly confirmed by the proof-of-principle experiments in mixed H?D plasmas on the Alcator C-Mod and JET tokamaks, using thermal 3He and fast D ions from neutral beam injection as resonant absorbers. Since 2018, significant progress has been made on the ASDEX Upgrade and JET tokamaks in H?4He and H?D plasmas, guided by the ITER needs. Furthermore, the scenario was also successfully applied in JET D?3He plasmas as a technique to generate fusion-born alpha particles and study effects of fast ions on plasma confinement under ITER-relevant plasma heating conditions. Tuned for the central deposition of ICRF power in a small region in the plasma core of large devices such as JET, three-ion ICRF scenarios are efficient in generating large populations of passing fast ions and modifying the q-profile. Recent experimental and modeling developments have expanded the use of three-ion scenarios from dedicated ICRF studies to a flexible tool with a broad range of different applications in fusion research. The authors are grateful to the anonymous reviewers for their constructive comments that allowed us to improve the paper, I. Voitsekhovitch for her valuable comments and suggestions during the paper preparation, and to H. Meyer and J. Faustin for fruitful discussions. We thank the ITPA Energetic Particle Physics Topical Group for its support. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. Part of this work was also carried out in the framework of projects done for the ITER Scientist Fellow Network (ISFN). ITER is the Nuclear Facility INB No. 174. The views and opinions expressed herein do not necessarily reflect those of the ITER Organization. This publication is provided for scientific purposes only. Its contents should not be considered as commitments from the ITER Organization as a nuclear operator in the frame of the licensing process. Peer Reviewed "Article signat per 67 autors/es: Ye. O. Kazakov, J. Ongena, J. C. Wright, S. J. Wukitch, V. Bobkov, J. Garcia, V. G. Kiptily, M. J. Mantsinen, M. Nocente, M. Schneider, H. Weisen, Y. Baranov, M. Baruzzo, R. Bilato, A. Chomiczewska, R. Coelho, T. Craciunescu K. Crombé, M. Dreval, R. Dumont, P. Dumortier, F. Durodié, J. Eriksson, M. Fitzgerald, J. Galdon-Quiroga, D. Gallart, M. Garcia-Muñoz, L. Giacomelli, C. Giroud, J. Gonzalez-Martin, A. Hakola, P. Jacquet, T. Johnson, A. Kappatou, D. Keeling, D. King, K. K. Kirov, P. Lamalle, M. Lennholm, E. Lerche, M. Maslov, S. Mazzi, S. Menmuir, I. Monakhov5, F. Nabais, M. F. F. Nave, R. Ochoukov, A. R. Polevoi, S. D. Pinches, U. Plank, D. Rigamonti, M. Salewski, P. A. Schneider, S. E. Sharapov, Ž. Štancar, A. Thorman, D. Valcarcel, D. Van Eester, M. Van Schoor, J. Varje, M. Weiland, N. Wendler, JET Contributors, ASDEX Upgrade Team, EUROfusion MST1 Team, and Alcator C-Mod Team" more...

In recent years, a new inversion method has been adapted to JET tomographic diagnostics. It is based on the Maximum Likelihood (ML) approach and has been applied to most systems of interest: the neutron, gamma ray and bolometric tomographies. In addition to its accuracy and reliability, the main competitive advantage of the ML inversion is the fact that it can provide reliable estimates of the uncertainties in the reconstructions. Recently the same approach has been deployed for the investigation of the hard X-rays and gamma rays, emitted by beams of runaway electrons during disruptions. This application is a particularly challenging proposition, given the potential detrimental effects of the errors in the magnetic topology, during the current quench. In this perspective, particular attention has been devoted to producing good quality, high time resolution equilibria. The ML inversion technique has given promising results and the developed routines have the potential of constituting a good complement to the other diagnostics, such as the infrared cameras, typically used to investigate the runaway electrons. more...

Nowadays, scientists are increasingly asked to investigate problems, which require the analysis of irregular, chaotic, non-stationary and corrupted time series. Assessing the causal relations between such signals is particularly challenging and, in many instances, interventions and experiments are impossible or impractical. The present work is a contribution to the development of indicators to quantify the mutual influences between time series. The criterion is called Cross Markov Matrix and belongs to the strand of techniques based on the conversion of time series into complex networks and the subsequent analysis of their topological properties. The proposed indicator is quite competitive with the available tools and can complement them very effectively. Indeed, all techniques have their strong and weak points and therefore corroborating the conclusions with mathematically independent methods is a recommended practice. The properties of the Cross Markov Matrix have been investigated with the help of a systematic series of numerical tests using synthetic data. The potential of the approach is then substantiated by the analysis of various real-life examples, ranging from environmental and global climate problems to the mutual influence between media coverage of Brexit and the pound-euro exchange rate. more...

A new tangential gamma-ray spectrometer has been developed for fast ion measurements in deuterium and deuterium-tritium plasmas of the Joint European Torus (JET). The instrument is based on a LaBr3 crystal with a photo-multiplier tube and replaces a pre-existing bismuth germanate detector, providing enhanced energy resolution and a counting rate capability in the MHz range. The line of sight is equipped with a LiH attenuator, which reduces the background due to 14 MeV neutron interactions with the crystal by more than two orders of magnitude and enables the observation of gamma-ray emission from confined α particles in JET deuterium-tritium plasmas. Thanks to its tangential line of sight, the detector can distinguish co- and counter-passing ions. The performance of the instrument is demonstrated through the results of recent JET fast ion experiments in deuterium plasmas. more...

The Joint European Torus (JET) gamma-ray camera has been recently upgraded with the installation of new gamma-ray detectors, based on LaBr3(Ce) scintillation crystals, which add spectroscopic capability to the existing system allowing measurements with good energy resolution (5% at 0.622 MeV), a dynamic range from hundreds of keV up to about 30 MeV, and high counting rate capabilities of MCps. First gamma-ray measurements during the C38 campaign of the JET have been successfully carried out, in particular, in D-3He plasmas from three-ion ion cyclotron resonance heating experiments, where the detection of 16.4 MeV γ-rays from D + 3He → γ + 5Li reactions with the gamma-ray camera upgrade allowed determining the spatial profile of alpha particles born in D + 3He fusion reactions. more...

We present a study of the power threshold for L–H transitions (PLH) in almost pure helium plasmas, obtained in recent experiments at JET with an ITER-like wall (Be wall and W divertor). The most notable new result is that the density at which PLH is minimum, ${\bar{n}}_{\text{e},\mathrm{min}}$, is considerably higher for helium than for deuterium and hydrogen plasmas. We discuss the possible implications for ITER in its pre-fusion operating power phase. more...

On the route to the commercial reactor, the experiments in magnetical confinement nuclear fusion have become increasingly complex and they tend to produce huge amounts of data. New analysis tools have therefore become indispensable, to fully exploit the information generated by the most relevant devices, which are nowadays very expensive to both build and operate. The paper presents a series of innovative tools to cover the main aspects of any scientific investigation. Causality detection techniques can help identify the right causes of phenomena and can become very useful in the optimisation of synchronisation experiments, such as the pacing of sawteeth instabilities with ion cyclotron radiofrequency heating modulation. Data driven theory is meant to go beyond traditional machine learning tools, to provide interpretable and physically meaningful models. The application to very severe problems for the tokamak configuration, such as disruptions, could help not only in understanding the physics but also in extrapolating the solutions to the next generation of devices. A specific methodology has also been developed to support the design of new experiments, proving that the same progress in the derivation of empirical models could be achieved with a significantly reduced number of discharges. more...

The next generation of Tokamak devices is expected to work at very high radiated fractions, well above 90%, to preserve the integrity of the plasma facing components in general and the divertor in particular. In addition to maintaining high confinement, these configurations will also have to guarantee a low disruptivity. An accurate determination of the emitted radiation will therefore become increasingly important, not only for the global power balances but also for specific regions of the plasma cross section (for example to properly control detachment). In this perspective, a new tomographic inversion method, based on the maximum likelihood (ML) approach, capable of providing routinely confidence intervals in the estimates of the radiated power, has been applied to the investigation of high radiative discharges on JET with the ITER like wall (ILW). The emission has been increased with injection of extrinsic impurities. Taking into account all the major sources of uncertainties, a systematic analysis of the configurations has shown that it has not been possible to develop stable configurations with radiated fraction higher than 70% of the input power. At higher radiated fractions the discharges always disrupt. Therefore significant work remains to be done to extend JET operation in a reactor relevant regime of sufficient radiation in preparation for ITER and DEMO. more...

The application of data driven machine learning and advanced statistical tools to complex physics experiments, such as Magnetic Confinement Nuclear Fusion, can be problematic, due the varying conditions of the systems to be studied. In particular, new experiments have to be planned in unexplored regions of the operational space. As a consequence, care must be taken because the input quantities used to train and test the performance of the analysis tools are not necessarily sampled by the same probability distribution as in the final applications. The regressors and dependent variables cannot therefore be assumed to verify the i.i.d. (independent and identical distribution) hypothesis and learning has therefore to take place under non stationary conditions. In the present paper, a new data driven methodology is proposed to guide planning of experiments, to explore the operational space and to optimise performance. The approach is based on the falsification of existing models. The deployment of Symbolic Regression via Genetic Programming to the available data is used to identify a set of candidate models, using the method of the Pareto Frontier. The confidence intervals for the predictions of such models are then used to find the best region of the parameter space for their falsification, where the next set of experiments can be most profitably carried out. Extensive numerical tests and applications to the scaling laws in Tokamaks prove the viability of the proposed methodology. more...

openaire: EC/H2020/633053/EU//EUROfusion Dedicated experiments were conducted in mixed H-D plasmas in JET to demonstrate the efficiency of the 3-ion ICRF scenario for plasma heating, relying on injected fast NBI ions as the resonant ion component. Strong core localization of the RF power deposition in the close vicinity of the ion-ion hybrid layer was achieved, resulting in an efficient plasma heating, generation of energetic D ions, strong enhancement of the neutron rate and observation of Alfvénic modes. A consistent physical picture that emerged from a range of fast-ion measurements at JET, including neutron and gamma-ray measurements, a high-energy neutral particle analyzer and MHD mode localization analysis, is presented. The possibility to moderate the fast-ion energies with the ratio P ICRF/P NBI and the choice of the NBI injectors is demonstrated. An outlook of possible applications of the 3-ion scenarios, including a recent example of its use in mixed D-3He plasmas in JET and promising scenarios for D-T plasmas, are presented. more...

Essential physical quantities of magnetically confined plasmas are derived on a routine basis from bolometric reconstructions. In the last few years at the Joint European Torus (JET), the Maximum Likelihood method has demonstrated the capability of providing reliable reconstructions for this class of ill-posed problems. The article is focused on quantifying the effects of important sources of errors, usually underestimated, that can influence both the reconstructions and the derived quantities. A complete set of phantoms has been used to test the robustness of the technique. The main sources of uncertainties investigated in this contribution are random noise, presence of outliers in the measurements, uncertainty of the position of the magnetic topology, and missing measurements from damaged or unreliable bolometers. The study provides a comprehensive quantification of the uncertainties to associate with most typical emissivities encountered in practice and constitutes a good basis for a more accurate evaluation of the power balances on the JET. Published under license by AIP Publishing. more...

The last years have witnessed on JET a significant increase in the use of digital cameras, which are routinely applied for imaging in the IR and visible spectral regions. One of the main technical difficulties, in interpreting the data of camera based diagnostics, is the presence of movements of the field of view. Small movements occur due to machine shaking during normal pulses while large ones may arise during disruptions. Some cameras show a correlation of image movement with change of magnetic field strength. For deriving unaltered information from the videos and for allowing correct interpretation, an image registration method, based on highly distinctive Scale Invariant Feature Transform (SIFT) descriptors and on the Coherent Point Drift (CPD) points set registration technique, has been developed. The method ensures a reliable determination of the alignment parameters and their corresponding uncertainty. The algorithm incorporates a complex procedure for rejecting outliers. The method has been applied for vibrations correction to a representative set of videos collected by the JET wide angle infrared camera. It proved to provide reliable image vibration correction when the camera is operated in full view. Another application has been developed for the JET fast visible camera, where the image rotation artefacts occur due to the sensitivity of the image intensifier to the magnetic field (above a certain threshold). The method has proved to be able to deal with the images provided by this camera frequently characterized by low contrast and a high level of blurring and noise. It has also the advantage of using directly the input images as they are provided by the cameras without any pre-processing step. The parameters of the algorithm are the same for all videos in the database. more...

Operation and data acquisition of an X-ray microtomography developed at INFLPR are optimized to produce stacks of 2-D high-resolution tomographic sections of Cable in Conduit Conductor (CICC) type superconductors demanded in major fusion projects. High-resolution images for CCIC samples (486 NbTi&Cu strands of 0.81 mm diameter, jacketed in rectangular stainless steel pipes of 22 × 26 mm 2 ) are obtained by a combination of high energy/intensity and small focus spot X-ray source and high resolution/efficiency detector array. The stack of reconstructed slices is then used for quantitative analysis consisting of accurate strand positioning, determination of the local and global void fraction and 3D strand trajectory assignment for relevant fragments of cable (∼300 mm). The strand positioning algorithm is based on the application of Gabor Annular filtering followed by local maxima detection. The local void fraction is extensively mapped by employing local segmentation methods at a space resolution of about 50 sub-cells sized to be relevant to the triplet of triplet twisting pattern. For the strand trajectory assignment part we developed a global algorithm of the linear programing type which provides the vast majority of correct strand trajectories for most practical applications. For carefully manufactured benchmark CCIC samples over 99% of the trajectories are correctly assigned. For production samples the efficiency of the algorithm is around 90%. Trajectory assignment of a high proportion of the strands is a crucial factor for the derivation of statistical properties of the cable such as twisting pattern, cos( θ ) or void fraction. more...

The total emission of radiation is a crucial quantity to calculate the power balances and to understand the physics of any Tokamak. Bolometric systems are the main tool to measure this important physical quantity through quite sophisticated tomographic inversion methods. On the Joint European Torus, the coverage of the bolometric diagnostic, due to the availability of basically only two projection angles, is quite limited, rendering the inversion a very ill-posed mathematical problem. A new approach, based on the maximum likelihood, has therefore been developed and implemented to alleviate one of the major weaknesses of traditional tomographic techniques: the difficulty to determine routinely the confidence intervals in the results. The method has been validated by numerical simulations with phantoms to assess the quality of the results and to optimise the configuration of the parameters for the main types of emissivity encountered experimentally. The typical levels of statistical errors, which may significantly influence the quality of the reconstructions, have been identified. The systematic tests with phantoms indicate that the errors in the reconstructions are quite limited and their effect on the total radiated power remains well below 10%. A comparison with other approaches to the inversion and to the regularization has also been performed. more...

Experiments using columns packed with calcite grains (size 1–2 mm) were carried out to study the behavior of passive treatment systems designed to remediate contaminated water from acid mine drainage (AMD). Two types of synthetic acidic solutions (H2SO4) were injected in the columns: (1) iron-rich with Fe(III) at pH 2, and (2) aluminum-rich at pH 2 and 3. Fluid flow was constant during the experiments with Darcy velocities ranging from 6 × 10−4 to 1 × 10−3 L m−2 s−1. The columns worked efficiently removing aqueous iron and aluminum as long as calcite dissolved and buffered the solution pH (increasing pH and promoting the precipitation of Fe(III)- or Al-oxyhydroxides). However, Ca released from dissolving calcite, along with the sulfate in solution, led to formation of gypsum coatings on the calcite grain surfaces which eventually prevented calcite dissolution. This passivation process limited the efficiency of the columns. Larger input sulfate concentrations or higher pH led to shorter passivation times. Characterization of the pore structure and composition by X-ray microtomography (mCT) and X-ray microdiffraction (mXRD) showed the precipitation of gypsum coatings on the calcite grains and secondary oxyhydroxides between the grains. This secondary mineral precipitation favored the formation of preferential flow paths, isolating regions of non-reacted limestone. An improved experimental design (mixing limestone grains and glass beads) minimized the formation of these preferential flow paths. Experimental results have been modeled with the CrunchFlow reactive transport code. Fitting of the results required a decrease in the reactive surface area of calcite, which is consistent with the passivation process. more...

An original spot detection method for large surveys of videos in Joint European Torus (JET) is presented. The method can be used for the automatic identification of spots in JET infra-red (IR) videos and for the assessment of the long-term trends in their evolution. This method has been applied to the analysis of a large database of JET IR images collected during the last campaigns of operation with the International Thermonuclear Experimental Reactor-like wall. The evolution of the spots and their properties, such as size and distribution, can be correlated with macroscopic events, in particular series of intentional disruptions. On the other hand, care must be taken in the interpretation of the results because there is some evidence of toroidal asymmetries in the spot distribution. more...

Different types of SiC–W composites have been realized by spark plasma sintering in a single step process starting with beta SiC nanometric powder, W nanometric and micrometric sized powders, and W foils. SEM, EDX, XRD and X-ray tomography have been used to analyze the sample morphology while the thermal properties of the resulting materials have been investigated up to 1000 °C using a LFA thermal analyzer. The results show the possibility to produce dense W–SiC composites, with enhanced thermal conductivity using a relatively simple route. more...

Due to their mechanical strength and ability to withstand the large electromagnetic force applied to the superconductors in large magnets during excitation, the Cable-in-Conduit-Conductor (CICC) type superconductors will be employed in the next stage of fusion magnets. Here, we discuss the recent results on the application of a non-invasive method for the characterization of CCIC by X-ray micro-tomography (μXCT). The experiments have been carried out on a high resolution X-ray tomograph in INFLPR ( http://tomography.inflpr.ro ). An open type nanofocus X-ray source with maximum high voltage of 225 kVp at 15–30 W maximum power and multiple targets of W on different windows materials (Be, Al, Cu or diamond) is the main component. X-rays are detected by means of amorphous silicon flat panel sensor in the cone-beam configuration and high-energy efficient line sensor based on individual scintillators in the fan-beam scanning configuration. The quality of tomographic images (≈40 μm space resolution) allowed the majority of strands of analyzed CICC samples to be fully reconstructed along the investigated segment (up to 300 mm long). Our method provides: (i) local and global void fractions (over a 300 mm length of the sample), (ii) void homogeneity factor as the ratio between void space surface and perimeter and (iii) twist pitch angle of individual strands and its distribution in 3D. It can be used to investigate superconducting CICC during their manufacture, installation or after service inspection, for purposes of QA, characterization or development. more...

The JET gamma-ray diagnostics system provides information on the behaviour of fast particles within the tokamak plasma. Information on the spatial distribution of the interacting fast particles is obtained from the gamma-ray cameras, while energy distribution information is provided by gamma-ray spectrometers. These techniques have been successfully applied so far in fast particle simulation experiments at JET. The extension of these diagnostics to high performance discharges with high neutron yields is not straightforward due to the background gamma-ray emission induced by neutrons. Two gamma-ray diagnostics upgrade projects at JET addressed this issue by developing neutron/gamma radiation filters ("neutron attenuators") and collimators for a proper definition of the radiation (neutron and gamma) fields along the diagnostics line-of-sight. A pair of neutron/gamma collimators working in a tandem configuration have been designed and constructed for the JET quasi-tangential gamma-ray spectrometer. The tandem collimators were designed to provide shielding factors of about 5 x 10(2) for 2.45 MeV neutrons and about 10(3) for 9 MeV gamma-rays. The devices have been installed on the JET machine and the paper presents the first experimental results. A similar tandem collimator system was designed for deuterium-tritium experiments on JET. The results of neutron-photon transport calculations for 14.1 MeV neutrons are also presented. (C) 2013 Published by Elsevier B.V. more...

In metallic machines ICRH heating is playing an increasingly important role. One of its most recent applications on the Joint Europena Torus (JET) is sawtooth control by ICRH modulation, for avoiding triggering dangerous neo-classical tearing modes (NTMs) and counteracting impurity accumulation. Some of the main difficulties of these experiments are the assessment of the synchronization efficiency and the understanding of the main physical mechanisms at play. In this paper, three independent classes of statistical indicators are introduced to address these issues: Recurrence Plots, Convergent Cross Mapping and Transfer Entropy. The application to JET experiments with the ILW shows that the proposed indicators agree quite well among themselves and provide sound estimates of the efficiency of the synchronisation scheme investigated. They also support, with a shot to shot basis analysis and an estimate of the uncertainties, the interpretation that the fast ions play a fundamental role in the stabilization of the sawteeth, in both L and H mode. Proposals for experiments to be carried out in the future to consolidate the interpretation of the results are discussed. more...

The JET tangential gamma-ray spectrometer is undergoing an extensive upgrade in order to make it compatible with the forthcoming deuterium-tritium (DT) experiments. The paper presents the results of the design for the main components for the upgrade of the spectrometer beam-line: tandem collimators, gamma-ray shields, and neutron attenuators. The existing tandem collimators will be upgraded by installing two additional collimator modules. Two gamma-ray shields will define the gamma-ray field of-view at the detector end of the spectrometer line-of-sight. A set of three lithium hydride neutron attenuators will be used to control the level of the fast neutron flux on the gamma-ray detector. The design of the upgraded spectrometer beam-line has been supported by extensive radiation (neutron and photon) transport calculations using both large volume and point radiation sources. For complete list of authors see http://dx.doi.org/10.1016/j.fusengdes.2017.05.064 more...

The 2014–2016 JET results are reviewed in the light of their significance for optimising the ITER research plan for the active and non-active operation. More than 60 h of plasma operation with ITER first wall materials successfully took place since its installation in 2011. New multi-machine scaling of the type I-ELM divertor energy flux density to ITER is supported by first principle modelling. ITER relevant disruption experiments and first principle modelling are reported with a set of three disruption mitigation valves mimicking the ITER setup. Insights of the L–H power threshold in Deuterium and Hydrogen are given, stressing the importance of the magnetic configurations and the recent measurements of fine-scale structures in the edge radial electric. Dimensionless scans of the core and pedestal confinement provide new information to elucidate the importance of the first wall material on the fusion performance. H-mode plasmas at ITER triangularity (H = 1 at ßN ~ 1.8 and n/nGW ~ 0.6) have been sustained at 2 MA during 5 s. The ITER neutronics codes have been validated on high performance experiments. Prospects for the coming D–T campaign and 14 MeV neutron calibration strategy are reviewed. This work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 under grant agreement No 633053. Peer Reviewed Article signat per 1.173 autors/es: X. Litaudon35, S. Abduallev39, M. Abhangi46, P. Abreu53, M. Afzal7, K.M. Aggarwal29, T. Ahlgren101, J.H. Ahn8, L. Aho-Mantila112, N. Aiba69, M. Airila112, R. Albanese105, V. Aldred7, D. Alegre93, E. Alessi45, P. Aleynikov55, A. Alfier12, A. Alkseev72, M. Allinson7, B. Alper7, E. Alves53, G. Ambrosino105, R. Ambrosino106, L. Amicucci90, V. Amosov88, E. Andersson Sundén22, M. Angelone90, M. Anghel85, C. Angioni62, L. Appel7, C. Appelbee7, P. Arena30, M. Ariola106, H. Arnichand8, S. Arshad41, A. Ash7, N. Ashikawa68, V. Aslanyan64, O. Asunta1, F. Auriemma12, Y. Austin7, L. Avotina103, M.D. Axton7, C. Ayres7, M. Bacharis24, A. Baciero57, D. Baião53, S. Bailey7, A. Baker7, I. Balboa7, M. Balden62, N. Balshaw7, R. Bament7, J.W. Banks7, Y.F. Baranov7, M.A. Barnard7, D. Barnes7, M. Barnes27, R. Barnsley55, A. Baron Wiechec7, L. Barrera Orte34, M. Baruzzo12, V. Basiuk8, M. Bassan55, R. Bastow7, A. Batista53, P. Batistoni90, R. Baughan7, B. Bauvir55, L. Baylor73, B. Bazylev56, J. Beal110, P.S. Beaumont7, M. Beckers39, B. Beckett7, A. Becoulet8, N. Bekris35, M. Beldishevski7, K. Bell7, F. Belli90, M. Bellinger7, É. Belonohy62, N. Ben Ayed7, N.A. Benterman7, H. Bergsåker42, J. Bernardo53, M. Bernert62, M. Berry7, L. Bertalot55, C. Besliu7, M. Beurskens63, B. Bieg61, J. Bielecki47, T. Biewer73, M. Bigi12, P. Bílková50, F. Binda22, A. Bisoffi31, J.P.S. Bizarro53, C. Björkas101, J. Blackburn7, K. Blackman7, T.R. Blackman7, P. Blanchard33, P. Blatchford7, V. Bobkov62, A. Boboc7, G. Bodnár113, O. Bogar18, I. Bolshakova60, T. Bolzonella12, N. Bonanomi97, F. Bonelli56, J. Boom62, J. Booth7, D. Borba35,53, D. Borodin39, I. Borodkina39, A. Botrugno90, C. Bottereau8, P. Boulting7, C. Bourdelle8, M. Bowden7, C. Bower7, C. Bowman110, T. Boyce7, C. Boyd7, H.J. Boyer7, J.M.A. Bradshaw7, V. Braic87, R. Bravanec40, B. Breizman107, S. Bremond8, P.D. Brennan7, S. Breton8, A. Brett7, S. Brezinsek39, M.D.J. Bright7, M. Brix7, W. Broeckx78, M. Brombin12, A. Brosławski65, D.P.D. Brown7, M. Brown7, E. Bruno55, J. Bucalossi8, J. Buch46, J. Buchanan7, M.A. Buckley7, R. Budny76, H. Bufferand8, M. Bulman7, N. Bulmer7, P. Bunting7, P. Buratti90, A. Burckhart62, A. Buscarino30, A. Busse7, N.K. Butler7, I. Bykov42, J. Byrne7, P. Cahyna50, G. Calabrò90, I. Calvo57, Y. Camenen4, P. Camp7, D.C. Campling7, J. Cane7, B. Cannas17, A.J. Capel7, P.J. Card7, A. Cardinali90, P. Carman7, M. Carr7, D. Carralero62, L. Carraro12, B.B. Carvalho53, I. Carvalho53, P. Carvalho53, F.J. Casson7, C. Castaldo90, N. Catarino53, J. Caumont7, F. Causa90, R. Cavazzana12, K. Cave-Ayland7, M. Cavinato12, M. Cecconello22, S. Ceccuzzi90, E. Cecil76, A. Cenedese12, R. Cesario90, C.D. Challis7, M. Chandler7, D. Chandra46, C.S. Chang76, A. Chankin62, I.T. Chapman7, S.C. Chapman28, M. Chernyshova49, G. Chitarin12, G. Ciraolo8, D. Ciric7, J. Citrin38, F. Clairet8, E. Clark7, M. Clark7, R. Clarkson7, D. Clatworthy7, C. Clements7, M. Cleverly7, J.P. Coad7, P.A. Coates7, A. Cobalt7, V. Coccorese105, V. Cocilovo90, S. Coda33, R. Coelho53, J.W. Coenen39, I. Coffey29, L. Colas8, S. Collins7, D. Conka103, S. Conroy22, N. Conway7, D. Coombs7, D. Cooper7, S.R. Cooper7, C. Corradino30, Y. Corre8, G. Corrigan7, S. Cortes53, D. Coster62, A.S. Couchman7, M.P. Cox7, T. Craciunescu86, S. Cramp7, R. Craven7, F. Crisanti90, G. Croci97, D. Croft7, K. Crombé15, R. Crowe7, N. Cruz53, G. Cseh113, A. Cufar81, A. Cullen7, M. Curuia85, A. Czarnecka49, H. Dabirikhah7, P. Dalgliesh7, S. Dalley7, J. Dankowski47, D. Darrow76, O. Davies7, W. Davis55,76, C. Day56, I.E. Day7, M. De Bock55, A. de Castro57, E. de la Cal57, E. de la Luna57, G. De Masi12, J. L. de Pablos57, G. De Temmerman55, G. De Tommasi105, P. de Vries55, K. Deakin7, J. Deane7, F. Degli Agostini12, R. Dejarnac50, E. Delabie73, N. den Harder38, R.O. Dendy7, J. Denis8, P. Denner39, S. Devaux62,104, P. Devynck8, F. Di Maio55, A. Di Siena62, C. Di Troia90, P. Dinca86, R. D’Inca62, B. Ding51, T. Dittmar39, H. Doerk62, R.P. Doerner9, T. Donné34, S.E. Dorling7, S. Dormido-Canto93, S. Doswon7, D. Douai8, P.T. Doyle7, A. Drenik62,81, P. Drewelow63, P. Drews39, Ph. Duckworth55, R. Dumont8, P. Dumortier58, D. Dunai113, M. Dunne62, I. Ďuran50, F. Durodié58, P. Dutta46, B. P. Duval33, R. Dux62, K. Dylst78, N. Dzysiuk22, P.V. Edappala46, J. Edmond7, A.M. Edwards7, J. Edwards7, Th. Eich62, A. Ekedahl8, R. El-Jorf7, C.G. Elsmore7, M. Enachescu84, G. Ericsson22, F. Eriksson16, J. Eriksson22, L.G. Eriksson36, B. Esposito90, S. Esquembri94, H.G. Esser39, D. Esteve8, B. Evans7, G.E. Evans7, G. Evison7, G.D. Ewart7, D. Fagan7, M. Faitsch62, D. Falie86, A. Fanni17, A. Fasoli33, J. M. Faustin33, N. Fawlk7, L. Fazendeiro53, N. Fedorczak8, R.C. Felton7, K. Fenton7, A. Fernades53, H. Fernandes53, J. Ferreira53, J.A. Fessey7, O. Février8, O. Ficker50, A. Field7, S. Fietz62, A. Figueiredo53, J. Figueiredo53,35, A. Fil8, P. Finburg7, M. Firdaouss8, U. Fischer56, L. Fittill7, M. Fitzgerald7, D. Flammini90, J. Flanagan7, C. Fleming7, K. Flinders7, N. Fonnesu90, J. M. Fontdecaba57, A. Formisano79, L. Forsythe7, L. Fortuna30, E. Fortuna-Zalesna19, M. Fortune7, S. Foster7, T. Franke34, T. Franklin7, M. Frasca30, L. Frassinetti42, M. Freisinger39, R. Fresa98, D. Frigione90, V. Fuchs50, D. Fuller35, S. Futatani6, J. Fyvie7, K. Gál34,62, D. Galassi2, K. Gałązka49, J. Galdon-Quiroga92, J. Gallagher7, D. Gallart6, R. Galvão10, X. Gao51, Y. Gao39, J. Garcia8, A. Garcia-Carrasco42, M. García-Muñoz92, J.-L. Gardarein3, L. Garzotti7, P. Gaudio95, E. Gauthier8, D.F. Gear7, S.J. Gee7, B. Geiger62, M. Gelfusa95, S. Gerasimov7, G. Gervasini45, M. Gethins7, Z. Ghani7, M. Ghate46, M. Gherendi86, J.C. Giacalone8, L. Giacomelli45, C.S. Gibson7, T. Giegerich56, C. Gil8, L. Gil53, S. Gilligan7, D. Gin54, E. Giovannozzi90, J.B. Girardo8, C. Giroud7, G. Giruzzi8, S. Glöggler62, J. Godwin7, J. Goff7, P. Gohil43, V. Goloborod’ko102, R. Gomes53, B. Gonçalves53, M. Goniche8, M. Goodliffe7, A. Goodyear7, G. Gorini97, M. Gosk65, R. Goulding76, A. Goussarov78, R. Gowland7, B. Graham7, M.E. Graham7, J. P. Graves33, N. Grazier7, P. Grazier7, N.R. Green7, H. Greuner62, B. Grierson76, F.S. Griph7, C. Grisolia8, D. Grist7, M. Groth1, R. Grove73, C.N. Grundy7, J. Grzonka19, D. Guard7, C. Guérard34, C. Guillemaut8,53, R. Guirlet8, C. Gurl7, H.H. Utoh69, L.J. Hackett7, S. Hacquin8,35, A. Hagar7, R. Hager76, A. Hakola112, M. Halitovs103, S.J. Hall7, S.P. Hallworth Cook7, C. Hamlyn-Harris7, K. Hammond7, C. Harrington7, J. Harrison7, D. Harting7, F. Hasenbeck39, Y. Hatano108, D.R. Hatch107, T.D.V. Haupt7, J. Hawes7, N.C. Hawkes7, J. Hawkins7, P. Hawkins7, P.W. Haydon7, N. Hayter7, S. Hazel7, P.J.L. Heesterman7, K. Heinola101, C. Hellesen22, T. Hellsten42, W. Helou8, O.N. Hemming7, T.C. Hender7, M. Henderson55, S.S. Henderson21, R. Henriques53, D. Hepple7, G. Hermon7, P. Hertout8, C. Hidalgo57, E.G. Highcock27, M. Hill7, J. Hillairet8, J. Hillesheim7, D. Hillis73, K. Hizanidis70, A. Hjalmarsson22, J. Hobirk62, E. Hodille8, C.H.A. Hogben7, G.M.D. Hogeweij38, A. Hollingsworth7, S. Hollis7, D.A. Homfray7, J. Horáček50, G. Hornung15, A.R. Horton7, L.D. Horton36, L. Horvath110, S.P. Hotchin7, M.R. Hough7, P.J. Howarth7, A. Hubbard64, A. Huber39, V. Huber39, T.M. Huddleston7, M. Hughes7, G.T.A. Huijsmans55, C.L. Hunter7, P. Huynh8, A.M. Hynes7, D. Iglesias7, N. Imazawa69, F. Imbeaux8, M. Imríšek50, M. Incelli109, P. Innocente12, M. Irishkin8, I. Ivanova-Stanik49, S. Jachmich58,35, A.S. Jacobsen83, P. Jacquet7, J. Jansons103, A. Jardin8, A. Järvinen1, F. Jaulmes38, S. Jednoróg49, I. Jenkins7, C. Jeong20, I. Jepu86, E. Joffrin8, R. Johnson7, T. Johnson42, Jane Johnston7, L. Joita7, G. Jones7, T.T.C. Jones7, K.K. Hoshino69, A. Kallenbach62, K. Kamiya69, J. Kaniewski7, A. Kantor7, A. Kappatou62, J. Karhunen1, D. Karkinsky7, I. Karnowska7, M. Kaufman73, G. Kaveney7, Y. Kazakov58, V. Kazantzidis70, D.L. Keeling7, T. Keenan7, J. Keep7, M. Kempenaars7, C. Kennedy7, D. Kenny7, J. Kent7, O.N. Kent7, E. Khilkevich54, H.T. Kim35, H.S. Kim80, A. Kinch7, C. king7, D. King7, R.F. King7, D.J. Kinna7, V. Kiptily7, A. Kirk7, K. Kirov7, A. Kirschner39, G. Kizane103, C. Klepper73, A. Klix56, P. Knight7, S.J. Knipe7, S. Knott96, T. Kobuchi69, F. Köchl111, G. Kocsis113, I. Kodeli81, L. Kogan7, D. Kogut8, S. Koivuranta112, Y. Kominis70, M. Köppen39, B. Kos81, T. Koskela1, H.R. Koslowski39, M. Koubiti4, M. Kovari7, E. Kowalska-Strzęciwilk49, A. Krasilnikov88, V. Krasilnikov88, N. Krawczyk49, M. Kresina8, K. Krieger62, A. Krivska58, U. Kruezi7, I. Książek48, A. Kukushkin72, A. Kundu46, T. Kurki-Suonio1, S. Kwak20, R. Kwiatkowski65, O.J. Kwon13, L. Laguardia45, A. Lahtinen101, A. Laing7, N. Lam7, H.T. Lambertz39, C. Lane7, P.T. Lang62, S. Lanthaler33, J. Lapins103, A. Lasa101, J.R. Last7, E. Łaszyńska49, R. Lawless7, A. Lawson7, K.D. Lawson7, A. Lazaros70, E. Lazzaro45, J. Leddy110, S. Lee66, X. Lefebvre7, H.J. Leggate32, J. Lehmann7, M. Lehnen55, D. Leichtle41, P. Leichuer7, F. Leipold55,83, I. Lengar81, M. Lennholm36, E. Lerche58, A. Lescinskis103, S. Lesnoj7, E. Letellier7, M. Leyland110, W. Leysen78, L. Li39, Y. Liang39, J. Likonen112, J. Linke39, Ch. Linsmeier39, B. Lipschultz110, G. Liu55, Y. Liu51, V.P. Lo Schiavo105, T. Loarer8, A. Loarte55, R.C. Lobel7, B. Lomanowski1, P.J. Lomas7, J. Lönnroth1,35, J. M. López94, J. López-Razola57, R. Lorenzini12, U. Losada57, J.J. Lovell7, A.B. Loving7, C. Lowry36, T. Luce43, R.M.A. Lucock7, A. Lukin74, C. Luna5, M. Lungaroni95, C.P. Lungu86, M. Lungu86, A. Lunniss110, I. Lupelli7, A. Lyssoivan58, N. Macdonald7, P. Macheta7, K. Maczewa7, B. Magesh46, P. Maget8, C. Maggi7, H. Maier62, J. Mailloux7, T. Makkonen1, R. Makwana46, A. Malaquias53, A. Malizia95, P. Manas4, A. Manning7, M.E. Manso53, P. Mantica45, M. Mantsinen6, A. Manzanares91, Ph. Maquet55, Y. Marandet4, N. Marcenko88, C. Marchetto45, O. Marchuk39, M. Marinelli95, M. Marinucci90, T. Markovič50, D. Marocco90, L. Marot26, C.A. Marren7, R. Marshal7, A. Martin7, Y. Martin33, A. Martín de Aguilera57, F.J. Martínez93, J. R. Martín-Solís14, Y. Martynova39, S. Maruyama55, A. Masiello12, M. Maslov7, S. Matejcik18, M. Mattei79, G.F. Matthews7, F. Maviglia11, M. Mayer62, M.L. Mayoral34, T. May-Smith7, D. Mazon8, C. Mazzotta90, R. McAdams7, P.J. McCarthy96, K.G. McClements7, O. McCormack12, P.A. McCullen7, D. McDonald34, S. McIntosh7, R. McKean7, J. McKehon7, R.C. Meadows7, A. Meakins7, F. Medina57, M. Medland7, S. Medley7, S. Meigh7, A.G. Meigs7, G. Meisl62, S. Meitner73, L. Meneses53, S. Menmuir7,42, K. Mergia71, I.R. Merrigan7, Ph. Mertens39, S. Meshchaninov88, A. Messiaen58, H. Meyer7, S. Mianowski65, R. Michling55, D. Middleton-Gear7, J. Miettunen1, F. Militello7, E. Militello-Asp7, G. Miloshevsky77, F. Mink62, S. Minucci105, Y. Miyoshi69, J. Mlynář50, D. Molina8, I. Monakhov7, M. Moneti109, R. Mooney7, S. Moradi37, S. Mordijck43, L. Moreira7, R. Moreno57, F. Moro90, A.W. Morris7, J. Morris7, L. Moser26, S. Mosher73, D. Moulton7,1, A. Murari12,35, A. Muraro45, S. Murphy7, N.N. Asakura69, Y.S. Na80, F. Nabais53, R. Naish7, T. Nakano69, E. Nardon8, V. Naulin83, M.F.F. Nave53, I. Nedzelski53, G. Nemtsev88, F. Nespoli33, A. Neto41, R. Neu62, V.S. Neverov72, M. Newman7, K.J. Nicholls7, T. Nicolas33, A.H. Nielsen83, P. Nielsen12, E. Nilsson8, D. Nishijima99, C. Noble7, M. Nocente97, D. Nodwell7, K. Nordlund101, H. Nordman16, R. Nouailletas8, I. Nunes53, M. Oberkofler62, T. Odupitan7, M.T. Ogawa69, T. O’Gorman7, M. Okabayashi76, R. Olney7, O. Omolayo7, M. O’Mullane21, J. Ongena58, F. Orsitto11, J. Orszagh18, B.I. Oswuigwe7, R. Otin7, A. Owen7, R. Paccagnella12, N. Pace7, D. Pacella90, L.W. Packer7, A. Page7, E. Pajuste103, S. Palazzo30, S. Pamela7, S. Panja46, P. Papp18, R. Paprok50, V. Parail7, M. Park66, F. Parra Diaz27, M. Parsons73, R. Pasqualotto12, A. Patel7, S. Pathak46, D. Paton7, H. Patten33, A. Pau17, E. Pawelec48, C. Paz Soldan43, A. Peackoc36, I.J. Pearson7, S.-P. Pehkonen112, E. Peluso95, C. Penot55, A. Pereira57, R. Pereira53, P.P. Pereira Puglia7, C. Perez von Thun35,39, S. Peruzzo12, S. Peschanyi56, M. Peterka50, P. Petersson42, G. Petravich113, A. Petre84, N. Petrella7, V. Petržilka50, Y. Peysson8, D. Pfefferlé33, V. Philipps39, M. Pillon90, G. Pintsuk39, P. Piovesan12, A. Pires dos Reis52, L. Piron7, A. Pironti105, F. Pisano17, R. Pitts55, F. Pizzo79, V. Plyusnin53, N. Pomaro12, O.G. Pompilian86, P.J. Pool7, S. Popovichev7, M.T. Porfiri90, C. Porosnicu86, M. Porton7, G. Possnert22, S. Potzel62, T. Powell7, J. Pozzi7, V. Prajapati46, R. Prakash46, G. Prestopino95, D. Price7, M. Price7, R. Price7, P. Prior7, R. Proudfoot7, G. Pucella90, P. Puglia52, M.E. Puiatti12, D. Pulley7, K. Purahoo7, Th. Pütterich62, E. Rachlew25, M. Rack39, R. Ragona58, M.S.J. Rainford7, A. Rakha6, G. Ramogida90, S. Ranjan46, C.J. Rapson62, J.J. Rasmussen83, K. Rathod46, G. Rattá57, S. Ratynskaia82, G. Ravera90, C. Rayner7, M. Rebai97, D. Reece7, A. Reed7, D. Réfy113, B. Regan7, J. Regaña34, M. Reich62, N. Reid7, F. Reimold39, M. Reinhart34, M. Reinke110,73, D. Reiser39, D. Rendell7, C. Reux8, S.D.A. Reyes Cortes53, S. Reynolds7, V. Riccardo7, N. Richardson7, K. Riddle7, D. Rigamonti97, F.G. Rimini7, J. Risner73, M. Riva90, C. Roach7, R.J. Robins7, S.A. Robinson7, T. Robinson7, D.W. Robson7, R. Roccella55, R. Rodionov88, P. Rodrigues53, J. Rodriguez7, V. Rohde62, F. Romanelli90, M. Romanelli7, S. Romanelli7, J. Romazanov39, S. Rowe7, M. Rubel42, G. Rubinacci105, G. Rubino12, L. Ruchko52, M. Ruiz94, C. Ruset86, J. Rzadkiewicz65, S. Saarelma7, R. Sabot8, E. Safi101, P. Sagar7, G. Saibene41, F. Saint-Laurent8, M. Salewski83, A. Salmi112, R. Salmon7, F. Salzedas53, D. Samaddar7, U. Samm39, D. Sandiford7, P. Santa46, M.I.K. Santala1, B. Santos53, A. Santucci90, F. Sartori41, R. Sartori41, O. Sauter33, R. Scannell7, T. Schlummer39, K. Schmid62, V. Schmidt12, S. Schmuck7, M. Schneider8, K. Schöpf102, D. Schwörer32, S.D. Scott76, G. Sergienko39, M. Sertoli62, A. Shabbir15, S.E. Sharapov7, A. Shaw7, R. Shaw7, H. Sheikh7, A. Shepherd7, A. Shevelev54, A. Shumack38, G. Sias17, M. Sibbald7, B. Sieglin62, S. Silburn7, A. Silva53, C. Silva53, P.A. Simmons7, J. Simpson7, J. Simpson-Hutchinson7, A. Sinha46, S.K. Sipilä1, A.C.C. Sips36, P. Sirén112, A. Sirinelli55, H. Sjöstrand22, M. Skiba22, R. Skilton7, K. Slabkowska49, B. Slade7, N. Smith7, P.G. Smith7, R. Smith7, T.J. Smith7, M. Smithies110, L. Snoj81, S. Soare85, E. R. Solano35,57, A. Somers32, C. Sommariva8, P. Sonato12, A. Sopplesa12, J. Sousa53, C. Sozzi45, S. Spagnolo12, T. Spelzini7, F. Spineanu86, G. Stables7, I. Stamatelatos71, M.F. Stamp7, P. Staniec7, G. Stankūnas59, C. Stan-Sion84, M.J. Stead7, E. Stefanikova42, I. Stepanov58, A.V. Stephen7, M. Stephen46, A. Stevens7, B.D. Stevens7, J. Strachan76, P. Strand16, H.R. Strauss44, P. Ström42, G. Stubbs7, W. Studholme7, F. Subba75, H.P. Summers21, J. Svensson63, Ł. Świderski65, T. Szabolics113, M. Szawlowski49, G. Szepesi7, T.T. Suzuki69, B. Tál113, T. Tala112, A.R. Talbot7, S. Talebzadeh95, C. Taliercio12, P. Tamain8, C. Tame7, W. Tang76, M. Tardocchi45, L. Taroni12, D. Taylor7, K.A. Taylor7, D. Tegnered16, G. Telesca15, N. Teplova54, D. Terranova12, D. Testa33, E. Tholerus42, J. Thomas7, J.D. Thomas7, P. Thomas55, A. Thompson7, C.-A. Thompson7, V.K. Thompson7, L. Thorne7, A. Thornton7, A.S. Thrysøe83, P.A. Tigwell7, N. Tipton7, I. Tiseanu86, H. Tojo69, M. Tokitani67, P. Tolias82, M. Tomeš50, P. Tonner7, M. Towndrow7, P. Trimble7, M. Tripsky58, M. Tsalas38, P. Tsavalas71, D. Tskhakaya jun102, I. Turner7, M.M. Turner32, M. Turnyanskiy34, G. Tvalashvili7, S.G.J. Tyrrell7, A. Uccello45, Z. Ul-Abidin7, J. Uljanovs1, D. Ulyatt7, H. Urano69, I. Uytdenhouwen78, A.P. Vadgama7, D. Valcarcel7, M. Valentinuzzi8, M. Valisa12, P. Vallejos Olivares42, M. Valovic7, M. Van De Mortel7, D. Van Eester58, W. Van Renterghem78, G.J. van Rooij38, J. Varje1, S. Varoutis56, S. Vartanian8, K. Vasava46, T. Vasilopoulou71, J. Vega57, G. Verdoolaege58, R. Verhoeven7, C. Verona95, G. Verona Rinati95, E. Veshchev55, N. Vianello45, J. Vicente53, E. Viezzer62,92, S. Villari90, F. Villone100, P. Vincenzi12, I. Vinyar74, B. Viola90, A. Vitins103, Z. Vizvary7, M. Vlad86, I. Voitsekhovitch34, P. Vondráček50, N. Vora7, T. Vu8, W.W. Pires de Sa52, B. Wakeling7, C.W.F. Waldon7, N. Walkden7, M. Walker7, R. Walker7, M. Walsh55, E. Wang39, N. Wang39, S. Warder7, R.J. Warren7, J. Waterhouse7, N.W. Watkins28, C. Watts55, T. Wauters58, A. Weckmann42, J. Weiland23, H. Weisen33, M. Weiszflog22, C. Wellstood7, A.T. West7, M.R. Wheatley7, S. Whetham7, A.M. Whitehead7, B.D. Whitehead7, A.M. Widdowson7, S. Wiesen39, J. Wilkinson7, J. Williams7, M. Williams7, A.R. Wilson7, D.J. Wilson7, H.R. Wilson110, J. Wilson7, M. Wischmeier62, G. Withenshaw7, A. Withycombe7, D.M. Witts7, D. Wood7, R. Wood7, C. Woodley7, S. Wray7, J. Wright7, J.C. Wright64, J. Wu89, S. Wukitch64, A. Wynn110, T. Xu7, D. Yadikin16, W. Yanling39, L. Yao89, V. Yavorskij102, M.G. Yoo80, C. Young7, D. Young7, I.D. Young7, R. Young7, J. Zacks7, R. Zagorski49, F.S. Zaitsev18, R. Zanino75, A. Zarins103, K.D. Zastrow7, M. Zerbini90, W. Zhang62, Y. Zhou42, E. Zilli12, V. Zoita86, S. Zoletnik113, I. Zychor65 and JET Contributorsa // EUROfusion Consortium JET, Culham Science Centre, Abingdon, OX14 3DB, United Kingdom / 1 Aalto University, PO Box 14100, FIN-00076 Aalto, Finland / 2 Aix Marseille Université, CNRS, Centrale Marseille, M2P2 UMR 7340, 13451, Marseille, France / 3 Aix-Marseille Université, CNRS, IUSTI UMR 7343, 13013 Marseille, France / 4 Aix-Marseille Université, CNRS, PIIM, UMR 7345, 13013 Marseille, France / 5 Arizona State University, Tempe, AZ, United States of America / 6 Barcelona Supercomputing Center, Barcelona, Spain / 7 CCFE, Culham Science Centre, Abingdon, Oxon, OX14 3DB, United Kingdom / 8 CEA, IRFM, F-13108 Saint Paul Lez Durance, France / 9 Center for Energy Research, University of California at San Diego, La Jolla, CA 92093, United States of America / 10 Centro Brasileiro de Pesquisas Fisicas, Rua Xavier Sigaud, 160, Rio de Janeiro CEP 22290-180, Brazil / 11 Consorzio CREATE, Via Claudio 21, 80125 Napoli, Italy / 12 Consorzio RFX, corso Stati Uniti 4, 35127 Padova, Italy / 13 Daegu University, Jillyang, Gyeongsan, Gyeongbuk 712-174, Republic of Korea / 14 Departamento de Física, Universidad Carlos III de Madrid, 28911 Leganés, Madrid, Spain / 15 Department of Applied Physics UG (Ghent University) St-Pietersnieuwstraat 41 B-9000 Ghent, Belgium / 16 Department of Earth and Space Sciences, Chalmers University of Technology, SE-41296 Gothenburg, Sweden / 17 Department of Electrical and Electronic Engineering, University of Cagliari, Piazza d’Armi 09123, Cagliari, Italy / 18 Department of Experimental Physics, Faculty of Mathematics, Physics and Informatics Comenius University Mlynska dolina F2, 84248 Bratislava, Slovakia / 19 Department of Materials Science, Warsaw University of Technology, PL-01-152 Warsaw, Poland / 20 Department of Nuclear and Quantum Engineering, KAIST, Daejeon 34141, Korea / 21 Department of Physics and Applied Physics, University of Strathclyde, Glasgow, G4 ONG, United Kingdom / 22 Department of Physics and Astronomy, Uppsala University, SE-75120 Uppsala, Sweden / 23 Department of Physics, Chalmers University of Technology, SE-41296 Gothenburg, Sweden / 24 Department of Physics, Imperial College London, London, SW7 2AZ, United Kingdom / 25 Department of Physics, SCI, KTH, SE-10691 Stockholm, Sweden / 26 Department of Physics, University of Basel, Basel, Switzerland / 27 Department of Physics, University of Oxford, Oxford, OX1 2JD, United Kingdom / 28 Department of Physics, University of Warwick, Coventry, CV4 7AL, United Kingdom / 29 Department of Pure and Applied Physics, Queens University, Belfast, BT7 1NN, United Kingdom / 30 Dipartimento di Ingegneria Elettrica Elettronica e Informatica, Università degli Studi di Catania, 95125 Catania, Italy / 31 Dipartimento di Ingegneria Industriale, University of Trento, Trento, Italy / 32 Dublin City University (DCU), Dublin, Ireland / 33 Ecole Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-1015 Lausanne, Switzerland / 34 EUROfusion Programme Management Unit, Boltzmannstr. 2, 85748 Garching, Germany / 35 EUROfusion Programme Management Unit, Culham Science Centre, Culham, OX14 3DB, United Kingdom / 36 European Commission, B-1049 Brussels, Belgium / 37 Fluid and Plasma Dynamics, ULB—Campus Plaine—CP 231 Boulevard du Triomphe, 1050 Bruxelles, Belgium / 38 FOM Institute DIFFER, Eindhoven, Netherlands / 39 Forschungszentrum Jülich GmbH, Institut für Energie- und Klimaforschung—Plasmaphysik, 52425 Jülich, Germany / 40 Fourth State Research, 503 Lockhart Dr, Austin, TX, United States of America / 41 Fusion for Energy Joint Undertaking, Josep Pl. 2, Torres Diagonal Litoral B3, 08019, Barcelona, Spain / 42 Fusion Plasma Physics, EES, KTH, SE-10044 Stockholm, Sweden / 43 General Atomics, PO Box 85608, San Diego, CA 92186-5608, United States of America / 44 HRS Fusion, West Orange, NJ, United States of America / 45 IFP-CNR, via R. Cozzi 53, 20125 Milano, Italy / 46 Institute for Plasma Research, Bhat, Gandhinagar-382 428, Gujarat State, India / 47 Institute of Nuclear Physics, Radzikowskiego 152, 31-342 Kraków, Poland / 48 Institute of Physics, Opole University, Oleska 48, 45-052 Opole, Poland / 49 Institute of Plasma Physics and Laser Microfusion, Hery 23, 01-497 Warsaw, Poland / 50 Institute of Plasma Physics AS CR, Za Slovankou 1782/3, 182 00 Praha 8, Czechia / 51 Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, People’s Republic of China / 52 Instituto de Física, Universidade de São Paulo, Rua do Matão Travessa R Nr.187 CEP 05508-090 Cidade Universitária, São Paulo, Brasil / 53 Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Universidade de Lisboa, Lisboa, Portugal / 54 Ioffe Physico-Technical Institute, 26 Politekhnicheskaya, St Petersburg 194021, Russian Federation / 55 ITER Organization, Route de Vinon, CS 90 046, 13067 Saint Paul Lez Durance, France / 56 Karlsruhe Institute of Technology, PO Box 3640, D-76021 Karlsruhe, Germany / 57 Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain / 58 Laboratory for Plasma Physics Koninklijke Militaire School—Ecole Royale Militaire, Renaissancelaan 30 Avenue de la Renaissance B-1000, Brussels, Belgium / 59 Lithuanian energy institute, Breslaujos g. 3, LT-44403, Kaunas, Lithuania / 60 Magnetic Sensor Laboratory, Lviv Polytechnic National University, Lviv, Ukraine / 61 Maritime University of Szczecin, Waly Chrobrego 1-2, 70-500 Szczecin, Poland / 62 Max-Planck-Institut für Plasmaphysik, D-85748 Garching, Germany / 63 Max-Planck-Institut für Plasmaphysik, Teilinsitut Greifswald, D-17491 Greifswald, Germany / 64 MIT Plasma Science and Fusion Centre, Cambridge, MA 02139, United States of America / 65 National Centre for Nuclear Research (NCBJ), 05-400 Otwock-Świerk, Poland / 66 National Fusion Research Institute (NFRI), 169-148 Gwahak-ro, Yuseong-gu, Daejeon 305-806, Republic of Korea / 67 National Institute for Fusion Science, Oroshi, Toki, Gifu 509-5292, Japan / 68 National Institute for Fusion Science, Toki, 509-5292, Japan / 69 National Institutes for Quantum and Radiological Science and Technology, Naka, Ibaraki 311-0193, Japan / 70 National Technical University of Athens, Iroon Politechniou 9, 157 73 Zografou, Athens, Greece / 71 NCSR ‘Demokritos’, 153 10, Agia Paraskevi Attikis, Greece / 72 NRC Kurchatov Institute, 1 Kurchatov Square, Moscow 123182, Russian Federation / 73 Oak Ridge National Laboratory, Oak Ridge, TN 37831-6169, United States of America / 74 PELIN LLC, 27a, Gzhatskaya Ulitsa, Saint Petersburg, 195220, Russian Federation / 75 Politecnico di Torino, Corso Duca degli Abruzzi 24, I-10129 Torino, Italy / 76 Princeton Plasma Physics Laboratory, James Forrestal Campus, Princeton, NJ 08543, United States of America / 77 Purdue University, 610 Purdue Mall, West Lafayette, IN 47907, United States of America / 78 SCK-CEN, Nuclear Research Centre, 2400 Mol, Belgium / 79 Second University of Napoli, Consorzio CREATE, Via Claudio 21, 80125 Napoli, Italy / 80 Seoul National University, Shilim-Dong, Gwanak-Gu, Republic of Korea / 81 Slovenian Fusion Association (SFA), Jozef Stefan Institute, Jamova 39, SI-1000 Ljubljana, Slovenia / 82 Space and Plasma Physics, EES, KTH SE-100 44 Stockholm, Sweden / 83 Technical University of Denmark, Department of Physics, Bldg 309, DK-2800 Kgs Lyngby, Denmark / 84 The ‘Horia Hulubei’ National Institute for Physics and Nuclear Engineering, Magurele-Bucharest, Romania / 85 The National Institute for Cryogenics and Isotopic Technology, Ramnicu Valcea, Romania / 86 The National Institute for Laser, Plasma and Radiation Physics, Magurele-Bucharest, Romania / 87 The National Institute for Optoelectronics, Magurele-Bucharest, Romania / 88 Troitsk Insitute of Innovating and Thermonuclear Research (TRINITI), Troitsk 142190, Moscow Region, Russian Federation / 89 University of Electronic Science and Technology of China, Chengdu, People’s Republic of China / 90 Unità Tecnica Fusione, ENEA C. R. Frascati, via E. Fermi 45, 00044 Frascati (Roma), Italy / 91 Universidad Complutense de Madrid, Madrid, Spain / 92 Universidad de Sevilla, Sevilla, Spain / 93 Universidad Nacional de Educación a Distancia, Madrid, Spain / 94 Universidad Politécnica de Madrid, Grupo I2A2, Madrid, Spain / 95 Università di Roma Tor Vergata, Via del Politecnico 1, Roma, Italy / 96 University College Cork (UCC), Ireland / 97 University Milano-Bicocca, piazza della Scienza 3, 20126 Milano, Italy / 98 University of Basilicata, Consorzio CREATE, Via Claudio 21, 80125 Napoli, Italy / 99 University of California, 1111 Franklin St., Oakland, CA 94607, United States of America / 100 University of Cassino, Consorzio CREATE, Via Claudio 21, 80125 Napoli, Italy / 101 University of Helsinki, PO Box 43, FI-00014 University of Helsinki, Finland / 102 University of Innsbruck, Fusion@Österreichische Akademie der Wissenschaften (ÖAW), Innsbruck, Austria / 103 University of Latvia, 19 Raina Blvd., Riga, LV 1586, Latvia / 104 University of Lorraine, CNRS, UMR7198, YIJL, Nancy, France / 105 University of Napoli ‘Federico II’, Consorzio CREATE, Via Claudio 21, 80125 Napoli, Italy / 106 University of Napoli Parthenope, Consorzio CREATE, Via Claudio 21, 80125 Napoli, Italy / 107 University of Texas at Austin, Institute for Fusion Studies, Austin, TX 78712, United States of America / 108 University of Toyama, Toyama, 930-8555, Japan / 109 University of Tuscia, DEIM, Via del Paradiso 47, 01100 Viterbo, Italy / 110 University of York, Heslington, York YO10 5DD, United Kingdom / 111 Vienna University of Technology, Fusion@Österreichische Akademie der Wissenschaften (ÖAW), Austria / 112 VTT Technical Research Centre of Finland, PO Box 1000, FIN-02044 VTT, Finland / 113 Wigner Research Centre for Physics, PO Box 49, H-1525 Budapest, Hungary more...

Multifaceted asymmetric radiation from the edge (MARFE) instabilities may reduce confinement leading to harmful disruptions. They cause a significant increase in impurity radiation, and therefore, ... more...

Video cameras have recently become diagnostic tools widely used on Joint European Torus (JET) for fusion plasma diagnostic and control. Since video streams are usually compressed for storage, MPEG-2 compressed domain information is processed to obtain a very fast and reasonably accurate 2-D motion estimation of the video scenes for the JET diagnostics, whose computational costs are prohibitively high. These methods can be used for the manipulation of the large JET video databases and, in specific cases, even for real-time data processing. Plasma instabilities, which can trigger harmful disruptions, are detected and tracked by means of motion segmentation. Motion segmentation is used as a key contrivance to allow very fast optical flow estimation for the determination of the deuterium ice extrusion velocity of JET pellet injector. Experimental validation is performed on significant JET video data. more...

Quantitative characterization of the porosity structure of the carbon reinforced carbon fibre (CFC) materials is carried out by high resolution cone-beam X-ray micro-tomography (CBμCT). It is shown that CBμCT provides useful information pertaining to the in-depth fuel migration into carbon tiles function of the CFC material structure. The investigated materials comprised two types of non-irradiated CFC samples (former ITER reference CFC NB31 and JET CFC DMS780) and a series of CFC N11 samples in the frame of the Deuterium Inventory in Tore Supra (DITS) post-mortem analysis. A procedure for the quantitative evaluation of the CFC porosity factor has been introduced and tested. Useful information about the pores connectivity as well as the metal impregnation inside the CFC macroscopic pores, in case of heat sink region of the TS CFC, can be retrieved. The method can be used for the quality control monitoring of the new CFC ITER reference materials. more...

An optical flow method is applied to the study of several fusion plasma relevant issues, including plasma wall interactions. A multi-resolution coarse-to-fine procedure is used in order to cope with large displacements of objects between consecutive frames, characteristic of plasma images captured by JET fast visible camera. Occlusion modeling is also implemented. The method is able to provide good results for JET fast visible camera images which can be affected by saturation, discontinuous movement, reshaping of image objects, low gray-level in-depth resolution. Significant experimental cases concerning pellet injection, plasma filaments and MARFEs are analysed. The method is able to provide the real velocity for objects moving close to structures. more...

During the application, the active surface of the forging dies is subjected to intense mechanical and thermal stresses combined with chemical oxidation. The fatigue resistance is an important characteristic which limits the service lifetime of the forging tools. This characteristic was significantly improved by a combined treatment between laser alloying/dispersing and plasma nitriding. This treatment was developed for W1.2365 and W1.2344 steels using TiC and WC + Co powders as additive materials. The surface layers have been examined by optical microscopy, glow discharge optical spectrometry (GDOS), energy dispersive X-ray (EDX), X-ray microtomography and other techniques. The combined treatment was successfully applied to a number of 13 forging tools from 4 European Companies, leading to an increase of their lifetime by factors ranging between 180 and 270%. more...

The main aim of the JET KN3 gamma-ray cameras upgrade is the design of appropriate neutron/gamma-ray filters (“neutron attenuators”). Using the attenuation factor as the main design parameter a set of three neutron attenuators of different shape and attenuation length have been designed for the horizontal and vertical cameras. Pure light water was chosen as the attenuating material for the JET gamma-ray cameras. The operation of the KN3 neutron attenuators is controlled by an electro-pneumatic system. A full-scale prototype of the vertical camera neutron attenuator was constructed and tested. The mechanical behaviour of the attenuator structure subject to the forces and torques produced by the JET disruptions was analysed by means of the finite element analysis method. The radiation performance of the KN3 neutron attenuators as well as the response of the gamma-ray detectors have been addressed by means of neutron and gamma-ray transport calculations. more...

An inspection procedure to assess the mechanical integrity of IFMIF capsules and rigs during the irradiation campaign is necessary. In a number of experiments, we previously proved that X-ray tomography is a reliable solution for official inspections of the structural integrity of IFMIF complete assemblies before and after various tests (tensile, creep-fatigue, fracture toughness, crack growth, microstructure swelling). The next main challenge is to qualify the transmission microtomography inspection as a tool for non-destructive inspection during maintenance (beam-off) periods and after irradiation campaigns. The influence of the sample gamma radioactivity (produced by neutron activation during irradiation campaigns) on the tomographic reconstruction quality is investigated in this paper. The evaluation is performed for the specific configuration of newly manufactured IFMIF irradiation capsules. Experimental X-ray radiographic data together with simulated gamma radiographic images were considered. Latest activation data were incorporated. For the numerical simulations, a working environment able to provide a realistic numerical simulation was constructed on the basis of two well established Monte Carlo computer codes: SIMIND and ITS. The optimal parameters of the collimation system, essential for the investigation of the irradiated samples, were determined. It is proved that transmission tomography is practicable, providing good quality reconstruction which allows accurate geometrical measurements. The procedure developed for tomography of irradiated HFTM can be applied for the inspection of other irradiated structures for which X-ray tomography represents a non-destructive inspection technique (NDT). more...

The potential of X-ray micro-tomography in characterizing the relevant material issues as identified during manufacturing processes was investigated. For this purpose, the 3D X-ray micro-tomography (XµRT) analysis was applied to the characterization of structural integrity of Nb3Sn superconducting wires of differing topology and the evolution of the density distribution of ceramic samples manufactured by Field Assisted Sintering Techniques (FAST). The latter technique was used to consolidate the ceramic, metal (Ni) and composite powders (MgB2). The usual scanning electron microscope (SEM) technique was enhanced by the high resolution XµRT in order to describe the volumetric density distribution before sintering and at different moments of the thermal cycle. Two types of samples sintered Ni and high density MgB2 superconductors with typical volume of 0.8÷1.5⋅10-9 m3 were sampled at space resolution around 5µm. For the sintered Ni, the 3D reconstructed volumes revealed the grain connectivity, necks formation and particle rearrangement in the densification process. The XµRT analysis was essential in explaining the differences in superconducting properties of MgB2 samples in terms of different volumetric structures. For the Nb3Sn multifilamentary wire which is at basis of many practical superconductors, the 3D tomography enabled the determination of the number of inter-filament contacts as well as the twist-pitch parameter. Advantages of our method versus the invasive etching techniques for the determination of the twist-pitch parameter were outlined. more...