1,448 research outputs found

    Tritium distribution analysis of Be limiter tiles from JET-ITER like wall campaigns using imaging plate technique and β-ray induced X-ray spectrometry

    Get PDF
    Tritium (T) distribution on the plasma-facing surfaces (PFSs) and inside castellation of Be limiter tiles from the JET tokamak with the ITER-like wall (ILW) was analyzed using imaging plate (IP) technique and β-ray induced X-ray spectrometry (BIXS). Regarding to PFSs, the outer poloidal limiter (OPL) showed significantly higher T concentrations than the inner wall guard limiter (IWGL) and upper dump plate (DP). The concentration of T on OPL was high at the central part. However, deuterium (D) and metallic impurities showed maximum concentration at the edges. This difference in distributions indicated different deposition and retention mechanisms between T and D. In contrast, deposition profiles of T concentrations on the castellated surfaces extended up to ∼ 5 mm into the gap, i.e. were similar to those of D and metallic impurities found by ion beam analysis.Peer reviewe

    Evaluation of tritium retention in plasma facing components during JET tritium operations

    Get PDF
    An assessment of the tritium (T) inventory in plasma facing components (PFC) during JET T and deuterium-tritium (DT) operations is presented based on the most comprehensive ex situ fuel retention data set on JET PFCs from the 2015-2016 ILW3 operating period is presented. The global fuel retention is 4.19 x 10(23) D atoms, 0.19% of injected fuel. The inner divertor remains the region of highest fuel retention (46.5%). The T inventory in PFCs at the end of JET operations is calculated as 7.48 x 10(22) atoms and is informative for accountancy, clean-up efficacy and waste liability assessments. The T accumulation rate at the upper inner divertor during JET DT operations has been used to assess the requirements and frequency of operation of a new laser induced desorption diagnostic to be installed on JET for the final DT experiments in 2023.Peer reviewe

    Material migration and fuel retention studies during the JET carbon divertor campaigns

    Get PDF
    The first divertor was installed in the JET machine between 1992 and 1994 and was operated with carbon tiles and then beryllium tiles in 1994-5. Post-mortem studies after these first experiments demonstrated that most of the impurities deposited in the divertor originate in the main chamber, and that asymmetric deposition patterns generally favouring the inner divertor region result from drift in the scrape-off layer. A new monolithic divertor structure was installed in 1996 which produced heavy deposition at shadowed areas in the inner divertor corner, which is where the majority of the tritium was trapped by co-deposition during the deuterium-tritium experiment in 1997. Different divertor geometries have been tested since such as the Gas-Box and High-Delta divertors; a principle objective has been to predict plasma behaviour, transport and tritium retention in ITER. Transport modelling experiments were carried out at the end of four campaigns by puffing C-13-labelled methane, and a range of diagnostics such as quartz-microbalance and rotating collectors have been installed to add time resolution to the post-mortem analyses. The study of material migration after D-D and D-T campaigns clearly revealed important consequences of fuel retention in the presence of carbon walls. They gave a strong impulse to make a fundamental change of wall materials. In 2010 the carbon divertor and wall tiles were removed and replaced with tiles with Be or W surfaces for the ITER-Like Wall Project.EURATOM 633053RCUK Energy Programme P012450/

    Fusion Technology Activities at JET in Support of the ITER Program

    Get PDF
    AbstrAct Among the technological activities performed at JET in support of the scientific objectives of both JET and ITER, a significant effort is devoted to the investigation of the erosion, transport and deposition of wall materials, and of their fuel retention properties. With the analysis of wall tiles retrieved in the 2010 shutdown, the full characterization of the previous JET carbon wall is obtained. In order to confirm the expectations on properties of the new ITER-Like Wall (ILW) installed in 2011, a large number of marker tiles and profiled tiles have been prepared and installed both in the main wall and in the divertor. These will be retrieved from the vessel during a short shutdown at the end of 2012 and analysed. The major changes introduced by the new ILW materials in JET required also a new nuclear characterization of the machine. Neutronics measurements have been performed to obtain the neutron/g-ray field changes inside and outside the JET machine. The experimental data are also used to validate neutronics codes used in ITER design. A new calibration of neutron detectors, scheduled in the 2012 shutdown and adopting the same procedure as in ITER, has been prepared based on extensive neutronics calculations. IntroductIon The JET research program includes technological activities in support of the scientific objectives of both JET and ITER. To this purpose, in 2010-11 the JET machine has undergone a major change to replace the previous carbon wall with a new ITER-Like Wall (ILW) making use of beryllium and tungsten in plasma facing components The erosion/deposition of wall materials in JET is characterized by net erosion on the main chamber wall and outer divertor, and migration of eroded material mainly to the inner divertor. During the 2009-10 shutdown phase, dust was collected from JET vessel [2] and several removed tiles were selected for analysis of deposits and surface. In this paper, first results of analyses on tiles exposed in 2007-2009 are presented. Considering also all previous results of erosion and deposition studies, a full characterization of the C wall in JET will be derived for comparison with the new ILW. Presently, one of the major objectives of the JET program is the investigation of the wall material transport, erosion/deposition and the fuel retention properties in the ILW. It is expected from laboratory experiments that the main mechanism for the fuel retention in the ILW is co-deposition in Be-layers. Implantation is the main mechanism for the retention in W, but it is expected to play a negligible role in comparison with the Be co-deposition. In order to confirm these expectations, and the results obtained during first ILW plasmas from gas balance method The major changes introduced by the new ILW materials in JET required also a new nuclear characterization of the machine. Neutronics analyses have been performed to calculate the neutron/gray field changes inside and outside the machine, the material activation and the shutdown doserat

    Tritium distributions on W-coated divertor tiles used in the third JET ITER-like wall campaign

    Get PDF
    Tritium (T) distributions on tungsten (W)-coated plasma-facing tiles used in the third ITER-like wall campaign (2015-2016) of the Joint European Torus (JET) were examined by means of an imaging plate technique and beta-ray induced x-ray spectrometry, and they were compared with the distributions after the second (2013-2014) campaign. Strong enrichment of T in beryllium (Be) deposition layers was observed after the second campaign. In contrast, T distributions after the third campaign was more uniform though Be deposition layers were visually recognized. The one of the possible explanations is enhanced desorption of T from Be deposition layers due to higher tile temperatures caused by higher energy input in the third campaign.EURATOM 633053Japan Society for the Promotion of Science JP2628935

    AVALIAÇÃO DAS POLÍTICAS PÚBLICAS DE CONVIVÊNCIA COM OS EFEITOS DA SECA NA ZONA RURAL DO POVOADO DE BARRA NOVA, VÁRZEA DO POÇO, BAHIA

    Get PDF
    O presente artigo faz referência ao estudo avaliativo das políticas públicas de estímulo a convivência com os efeitos da seca no semiárido tendo como base a zona rural do entorno do povoado de Barra Nova, Várzea do Poço - BA. As políticas públicas de convivência com os efeitos das secas, representadas principalmente pelas tecnologias sociais de convivência com o semiárido, têm proporcionado às famílias beneficiadas, sobretudo as mais carentes, uma melhoria nas condições de vida, capacitando-as para conviverem harmonicamente com os períodos de estiagem. Os procedimentos metodológicos foram: levantamento de referencial bibliográfico e pesquisa de campo com a realização de registros fotográficos e entrevistas com os moradores da localidade e gestores dessas polícas no local

    Long-term fuel retention and release in JET ITER-Like Wall at ITER-relevant baking temperatures

    Get PDF
    The fuel outgassing efficiency from plasma-facing components exposed in JET-ILW has been studied at ITER-relevant baking temperatures. Samples retrieved from the W divertor and Be main chamber were annealed at 350 and 240 °C, respectively. Annealing was performed with thermal desoprtion spectrometry (TDS) for 0, 5 and 15 h to study the deuterium removal effectiveness at the nominal baking temperatures. The remained fraction was determined by emptying the samples fully of deuterium by heating W and Be samples up to 1000 and 775 °C, respectively. Results showed the deposits in the divertor having an increasing effect to the remaining retention at temperatures above baking. Highest remaining fractions 54 and 87% were observed with deposit thicknesses of 10 and 40 μm, respectively. Substantially high fractions were obtained in the main chamber samples from the deposit-free erosion zone of the limiter midplane, in which the dominant fuel retention mechanism is via implantation: 15 h annealing resulted in retained deuterium higher than 90%. TDS results from the divertor were simulated with TMAP7 calculations. The spectra were modelled with three deuterium activation energies resulting in good agreement with the experimentsEURATOM 63305

    High-fidelity patterning of AlN and ScAlN thin films with wet chemicaletching

    Get PDF
    We report on the anisotropic wet etching of sputtered AlN and Sc0.2Al0.8 N thin films. With tetramethyl ammonium hydroxide at 80 degrees C, the etch rates along the c-axis were 330 and 30 nm/s for AlN and Sc0.2Al0.8N, respectively. Although the etching was anisotropic, significant lateral etching below the mask occurred, perpendicular to the c-axis. With a 1 mu m Sc0.2Al0.8 N film, it could be up to 1800 nm. We studied the lateral etching with molybdenum, SiO2, SiNx and TiO2 masks, and found the leading cause for the lateral etching to be modification of the AlN or Sc0.2Al0.8 N surface caused by ion bombardment and surface oxidation by ambient air. The lateral etching was reduced by optimizing the mask deposition and with thermal annealing. With Sc0.2Al0.8 N, the lateral etching was reduced down to 35-220 nm depending on the mask, while with AlN, it was reduced to negligible. These results can be used for developing optimised mask deposition processes for better etch characteristics and for microfabrication of AlN and ScxAl1-xN thin-film structures.Peer reviewe

    The influence of carbon impurities on the formation of loops in tungsten irradiated with self-ions

    Get PDF
    The microstructure changes taking place in W under irradiation are governed by many factors, amongst which C impurities and their interactions with self-interstitial atoms (SIA). In this work, we specifically study this effect by conducting a dedicated 2-MeV self-ions irradiation experiment, at room temperature. Samples were irradiated up to 0.02, 0.15 and 1.2 dpa. Transmission electron microscopy (TEM) expectedly revealed a large density of SIA loops at all these doses. Surprisingly, however, the loop number density increased in a non-monotonous manner with the received dose. Performing chemical analysis with secondary ion spectroscopy measurements (SIMS), we find that our samples were likely contaminated by C injection during the irradiation. Employing an object kinetic Monte Carlo (OKMC) model for microstructure evolution, we demonstrate that the C injection is the likely factor explaining the evolution of loops number density. Our findings highlight the importance of the well-known issue of C injection during ion irradiation experiments, and demonstrate how OKMC models can help to rationalize this effect.Peer reviewe
    corecore