Evidence of large magneto-dielectric effect coupled to a metamagnetic transition in Yb2CoMnO6

The double perovskite Yb2CoMnO6 has been synthesized with an almost perfect checkerboard arrangement of Co2+ and Mn4+ cations in the B-sublattice of the perovskite cell. It presents an anomaly in the electric capacitance and a strong magneto-dielectric effect at about 40 K whose interplay with the microscopic magnetic behavior has been investigated by means of neutron diffraction, magnetization, pyroelectric, and relative dielectric permittivity measurements. We show that the onset of an E-type antiferromagnetic ordering of Co2+ and Mn4+ moments monitored by neutron diffraction provokes the noticeable jump of the relative dielectric permittivity (∼9%) at about 40 K. It is also shown that this jump can be totally suppressed by application of a magnetic field of μ0H = 5 T. Neutron experiments and magnetic measurements confirm that such a suppression leading to a significant magneto-dielectric effect is driven by a metamagnetic phase transition from the peculiar E-type ordering of 3d moments into a collinear ferromagnetic order. Pyroelectric current measurements do not show any spontaneous electric polarization, so the large dielectric anomaly at zero field cannot be ascribed to a ferroelectric ordering.We thank financial support from the Spanish MINECO (Project Nos. MAT2012-38213-C02-01 and MAT2012-38213-C02-02, cofunded by ERDF from EU) and Diputacion General de Aragon (DGA-CAMRADS). One of us (J.A.R.-V.) acknowledges CSIC for a JAEdoc contract.Peer Reviewe

Magnetoelectric and structural properties of Y2CoMnO6: The role of antisite defects

We have carried out an investigation on the magnetoelectric properties of the presumed multiferroic Y2CoMnO6 with different degrees of Co/Mn atomic ordering. The magnetic ground state was studied by neutron diffraction, showing a collinear ferromagnetic (FM) ordering of Co and Mn moments with a small antiferromagnetic canting. No superstructure peaks from an E-type magnetic structure were detected in our measurements. Magnetic measurements reveal FM transitions with pinned magnetic domains. The degree of Co/Mn ordering affects the Curie temperature only a little, but has strong effects on the magnetic hysteresis loops, and the FM moment signal at high field increases with increasing such order. The loops display steps at critical fields whose number and extent depends on each specimen. The most ordered sample exhibits the greatest steps ascribed to the alignment of magnetic domains separated by antiphase boundaries. All samples are insulators exhibiting low dielectric loss and dielectric constants at low temperature. On warming, they show a step increase in the real dielectric permittivity accompanied by peaks in the dielectric loss typical of thermally activated hopping processes. At room temperature, the huge values of the dielectric constant reveal the presence of Maxwell-Wagner depletion layers. Pyroelectric measurements reveal a high polarization at low temperature for these compounds that increases with increasing the Co/Mn ordering. There is no correlation between the magnetic transition and the onset of pyroelectric current. No significant changes are observed in the pyroelectric effect measured under an external magnetic field, so magnetoelectric coupling is negligible. This paper identifies the pyroelectric current as thermally stimulated depolarization current ascribed to the reorientation of defect dipoles with activation energy of about 0.05 eV. Therefore, no ferroelectric transition occurs in these compounds, discarding the existence of intrinsic magnetoelectric multiferroicity.For financial support we thank the Spanish Ministerio de Economía y Competitividad (MINECO) (Projects No. MAT2012-38213-C02-01 and -02 and No. MAT2015-68760-C1-1 and -2-P, cofunded by the European Regional Development Fund [ERDF] from the European Union) and Diputación General de Aragón (DGA, project E-69). J.A. Rodríguez-Velamazan acknowledges CSIC for the JAEdoc contract.Peer Reviewe

Un proyecto de inteligencia colectiva basado en la colaboración y en el conocimiento. El caso de repensar Extremadura

El proyecto Repensar Extremadura pretende acelerar la transferencia de conocimiento innovador y de transformación de un territorio, en este caso de la región de Extremadura (España). Desde una propuesta novedosa de participación ciudadana basada en la inteligencia colectiva, persigue detectar las nuevas ideas que van surgiendo en diferentes ámbitos, tales como económicos y sociales, e identificar nuevas oportunidades en base al establecimiento de retos presentes y futuros. La finalidad es que las nuevas ideas, desde el contraste académico y científico de la Universidad y de los Centros de Investigación, puedan estudiarse, valorarse y aplicarse en la región de Extremadura (España). Se propone un proceso permanente de reflexión tomando el conocimiento como la base de cualquier progreso social, en la que las instituciones, organizaciones, asociaciones e instituciones civiles desarrollan un papel clave en el proyecto para el establecimiento de nuevos modelos de desarrollo futuros, alineados con la Agenda 2030 para el Desarrollo Sostenible

Deposition of impurity metals during campaigns with the JET ITER-like Wall

Post mortem analysis shows that mid and high atomic number metallic impurities are present in deposits on JET plasma facing components with the highest amount of Ni and W, and therefore the largest sink, being found at the top of the inner divertor. Sources are defined as "continuous" or "specific", in that "continuous" sources arise from ongoing erosion from plasma facing surfaces and specific" are linked with specific events which decrease over time until they no longer act as a source. This contribution evaluates the sinks and estimates sources and the balance gives an indication of the dominating processes. Charge exchange neutral erosion is found to be the main source of nickel, whereas erosion of divertor plasma facing components is the main source of tungsten. Specific sources are shown to have little influence over the global mid- and high-Z impurity concentrations in deposits.EURATOM 633053RCUK Energy Programme EP/I50104

RF sheath modeling of experimentally observed plasma surface interactions with the JET ITER-Like Antenna

Waves in the Ion Cyclotron Range of Frequencies (ICRF) enhance local Plasma-Surface Interactions (PSI) near the wave launchers and magnetically-connected objects via Radio-Frequency (RF) sheath rectification. ITER will use 20MW of ICRF power over long pulses, questioning the long-term impact of RF-enhanced localized erosion on the lifetime of its Beryllium (Be) wall. Recent dedicated ICRF-heated L-mode discharges documented this process on JET for different types of ICRF antennas. Using visible spectroscopy in JET ICRF-heated L-mode discharges, poloidally-localized regions of enhanced (by ∼2–4x) Be I and Be II light emission were observed on two outboard limiters magnetically connected to the bottom of the active ITER-Like Antenna (ILA). The observed RF-PSI induced by the ILA was qualitatively comparable to that induced by the JET standard, type-A2 antennas, for similar strap toroidal phasing and connection geometries. The Be II line emission was found more intense when powering the bottom half of the ILA rather than its top half. Conversely, more pronounced SOL density modifications were observed with only top array operation, on field lines connected to the top half of the ILA. So far the near-field modeling of the ILA with antenna code TOPICA (Torino Polytechnic Ion Cyclotron Antenna), using curved antenna model, was partially able to reproduce qualitatively the observed phenomena. A quantitative discrepancy persisted between the observed Be source amplification and the calculated, corresponding increases in E// field at the magnetically connected locations to the ILA when changing from only top to only bottom half antenna operation. This paper revisits these current drive phased and half-ILA powered cases using for the new simulations flat model of the ILA and more realistic antenna feeding to calculate the E// field maps with TOPICA code. Further, the Self-consistent Sheaths and Waves for Ion Cyclotron Heating Slow Wave (SSWICH-SW) code, which couples slow wave evanescence with DC Scrape-Off Layer (SOL) biasing, is used to estimate the poloidal distribution of rectified RF-sheath Direct Current (DC) potential VDC in the private SOL between the ILA poloidal limiters. The approach so far was limited to correlating the observed, enhanced emission regions at the remote limiters to the antenna near-electric fields, as calculated by TOPICA. The present approach includes also a model for the rectification of these near-fields in the private SOL of the ILA. With the improved approach, when comparing only top and only bottom half antenna feeding, we obtained good qualitative correlation between all experimental measurements and the calculated local variations in the E// field and VDC potential.EURATOM 63305

Impact of fast ions on density peaking in JET: fluid and gyrokinetic modeling

The effect of fast ions on turbulent particle transport, driven by ion temperature gradient (ITG)/ trapped electron mode turbulence, is studied. Two neutral beam injection (NBI) heated JET discharges in different regimes are analyzed at the radial position ρt = 0.6, one of them an L-mode and the other one an H-mode discharge. Results obtained from the computationally efficient fluid model EDWM and the gyro-fluid model TGLF are compared to linear and nonlinear gyrokinetic GENE simulations as well as the experimentally obtained density peaking. In these models, the fast ions are treated as a dynamic species with a Maxwellian background distribution. The dependence of the zero particle flux density gradient (peaking factor) on fast ion density, temperature and corresponding gradients, is investigated. The simulations show that the inclusion of a fast ion species has a stabilizing influence on the ITG mode and reduces the peaking of the main ion and electron density profiles in the absence of sources. The models mostly reproduce the experimentally obtained density peaking for the L-mode discharge whereas the H-mode density peaking is significantly underpredicted, indicating the importance of the NBI particle source for the H-mode density profile.EURATOM 63305

A Novel Direct Load Control Testbed for Smart Appliances

The effort to continuously improve and innovate smart appliances (SA) energy management requires an experimental research and development environment which integrates widely differing tools and resources seamlessly. To this end, this paper proposes a novel Direct Load Control (DLC) testbed, aiming to conveniently support the research community, as well as analyzing and comparing their designs in a laboratory environment. Based on the LabVIEW computing platform, this original testbed enables access to knowledge of major components such as online weather forecasting information, distributed energy resources (e.g., energy storage, solar photovoltaic), dynamic electricity tariff from utilities and demand response (DR) providers together with different mathematical optimization features given by General Algebraic Modelling System (GAMS). This intercommunication is possible thanks to the different applications programming interfaces (API) incorporated into the system and to intermediate agents specially developed for this case. Different basic case studies have been presented to envision the possibilities of this system in the future and more complex scenarios, to actively support the DLC strategies. These measures will offer enough flexibility to minimize the impact on user comfort combined with support for multiple DR programs. Thus, given the successful results, this platform can lead to a solution towards more efficient use of energy in the residential environment

Investigation of deuterium trapping and release in the JET divertor during the third ILW campaign using TDS

Selected set of samples from JET ITER-Like Wall (JET-ILW) divertor tiles exposed in 2015–2016 has been analysed using Thermal Desorption Spectrometry (TDS). The deuterium (D) amounts obtained with TDS were compared with Nuclear Reaction Analysis (NRA). The highest amount of D was found on the top part of inner divertor which has regions with the thickest deposited layers as for divertor tiles removed in 2014. This area resides deep in the scrape-off layer and plasma configurations for the second (ILW-2, 2013–2014) and the third (ILW-3, 2015–2016) JET-ILW campaigns were similar. Agreement between TDS and NRA is good on the apron of Tile 1 and on the upper vertical region whereas on the lower vertical region of Tile 1 the NRA results are clearly smaller than the TDS results. Inner divertor Tile 3 has somewhat less D than Tiles 0 and 1, and the D amount decreases towards the lower part of the tile. The D retention at the divertor inner and outer corner regions is not symmetric as there is more D retention poloidally at the inner than at the outer divertor corner. In most cases the TDS spectra for the ILW-3 samples are different from the corresponding ILW-2 spectra because HD and D2 release occurs at higher temperatures than from the ILW-2 samples indicating that the low energy traps have been emptied during the plasma operations and that D is either in the energetically deep traps or located deeper in the sample.EURATOM 63305

First mirror test in JET for ITER: Complete overview after three ILW campaigns

The First Mirror Test for ITER has been carried out in JET with mirrors exposed during (1) the third IIW campaign (11.W-3, 2015-2016, 23.33 h plasma) and (ii) all three campaigns, Le LW1 to ILW-3: 20112016 63,52 h in total. All mirrors from main chamber wall show no significant changes of the total reflectivity from the initial value and the diffuse reflectivity does not exceed 3% in the spectral range above 500 nm. The modified Layer on surface has very small amount of impurities such as D, B, C N O and Ni. All mirrors from the divertor (inner, outer, base under the bulk ile) lost reflectivity by 20-80% due to the beryllium-rich deposition also containing D, CN, O, Ni and W. In the inner divertor N reaches 5 x 107 cm2 W is up to 4.3 x 10 cm while the content of Ni is the greatest in the outer divertor 3.8 x 10 cm Oxygen-18 used as the tracer in experiments at the end of ILW-3 has been detected at the level of 1.1 x 10 cm . The thickness of deposited Layer is in the range or 90 nm to 900 nm. The layer growth rate in the base (2.7 pms !) and inner divertor is proportional to the exposure time when a single campaign and all three are compared. In a few cases, on mirrots located at the cassette mouth, flaking of deposits and crosion occurred.EURATOM 63305

Investigation of deuterium trapping and release in the JET ITER-like wall divertor using TDS and TMAP

Selected set of samples from JET TER-Like Wall (JET-ILW) divertor tiles exposed both in 20132014 and 20112014 has been analysed using Thermal Desorption Spectrometry (TDS). The deuterium (D) amounts ob tained with TIS were compared with ion Beam Analysis (TBA) and Secondary ion Mass Spectrometry (SIMS) data. The hig amount of D was found on the top part of inner divertor which has regions with the thickest deposited layers. This area resides deep in the scrape-off layer. Changes in plasma configurations between the first 20112012 and the second 20132014 JET-IL W campaign altered the material migration towards the inner and the outer divertor come increasing the amount of deposition in the shadowed areas of the divertor base tiles. Retention on the outer divertor tiles is clearly smaller than on the inner divertor tiles. Experimental TDS spectra for samples from the top part of inner divertor and from the outer strike point region were modelled using TMAP program. Experimental deuterium profiles obtained with SIMS have been used and the detrapping and the activation energies have been adjusted Analysis of the results of the TMAP simulations enabled to determine the nature of traps in different samplesEURATOM 633053Finnish FundingAgency forTechnology and Innovation 4433/31/201