Modal analysis of the fields in the ITER ICRF antenna port plug cavity

The cavity that is formed between the ITER ICRF antenna plug and its port can exhibit resonances at specific fre-quencies, some of them in the relevant range of frequencies for IC heating. These resonances related to eigenmodes of the coaxial cavity, can substantially increase the level of electric fields inside the cavity and the level of RF losses in the B4C neutron shielding tiles at the back of the port-plug cavity can also be significant. For instance, in MWS simulations of a simplified geometry of the antenna in front of a dielectric mimicking the plasma loading, the level of RF losses in the B4C can reach tens of kW in 00ππ toroidal phasing and even larger values in monopole. RF probes will be installed to monitor the RF fields in the port plug cavity and additional simulations are required to properly assess the integration (position, orientation) and their effectiveness. A model with a very detailed geometry of the antenna was also used in Ansys HFSS and TOPICA simulations. On the one hand it is observed that the resistivity of the B4C neutron shielding material located at the back of the cavity has a marked effect on the excitation of the resonances and that for certain ranges of resistivity the numerical computation fails exhausting computer memory requirements (Ansys/HFSS) when trying to solve the total antenna and cavity problem as a single model. On the other hand lossy materials such as the B4C tiles cannot be represented in TOPICA models while a realistic plasma gyrotropic load can not be simulated in HFSS/MWS. Therefore, we introduced a modal analysis in the cavity to decouple solving the computationally intensive plasma-facing front of the launcher from the cavity. The fields computed by TOPICA for various loading conditions and frequencies are evaluated on a set of vertical planes in the cavity and expanded in a series of modal eigenmodes for a given mode of operation. This provides the necessary input for an accurate evaluation of the RF fields in the cavity in an independent model not including the antenna front-face. It will also contribute to the understanding of the impact of the relative toroidal phasing of the strap currents on the excitation of the cavity modes and to simulate accurately the response of the cavity RF probes

Visual feature extraction from dermoscopic colour images for classification of melanocytic skin lesions

The early diagnosis of Melanoma is a challenging task for dermatologists, because of the characteristic similarities of Melanoma with other skin lesions such as typical moles and dysplastic nevi. Aims: This work aims to help both experienced and non-experienced dermatologists in the early detection of cutaneous Melanoma through the development of a computational helping tool based on the “ABCD” rule of dermoscopy. Moreover, it aims to decrease the need for invasive biopsy procedure for each tested abnormal skin lesion. Methods: This is accomplished through the utilization of MATLAB programming language to build a feature extraction tool for the assessment of lesion asymmetry, borders irregularity, and colors variation in the tested lesion. Results: The helping tool obtained a sensitivity of 81.48%, a specificity of 52.83% and accuracy of 62.50% in the assessment of the Asymmetry Index. A new metric for the borders irregularity index was built. Finally, for the Colors Variation Index algorithm a sensitivity of 51.37%, a specificity of 61.51% and accuracy of 57.80% was achieved. Conclusions: This work created a computational tool based on the ABCD-rule, which is helpful for both experienced and non-experienced dermatologists in the early discrimination of Melanoma than other types of skin lesions and to eliminate the need of the biopsy procedure. A new metric for the Borders Irregularity Index was established depending on the number of inflection points in the lesion’s borders

Multi-strap in-port ICRF antenna modeling and development in support of ITER and EU-DEMO

Full-size 3D model of ITER ICRF antenna with 1D plasma electron density (ne) and 3D ne (from EMC3-Eirene) was simulated using the RAPLICASOL (COMSOL-based) code. Impedance matrices and coupled power agree well with TOPICA with 1D ne. Cases with 3D ne show port-to-port differences compared to 1D ne, as well as a lower (about 10%) coupled power. Efficient minimization of ITER antenna near-fields (to reduce RF sheaths by optimizing feeding) calculated by TOPICA and RAPLICASOL is possible with [0;π;π;0] (about balanced strap powers) and is even lower with [0;π;0;π] toroidal phasing (with dominant power from central straps). Lowest near-fields are with [0;π] poloidal phasing, but [0;-π/2] will be used in a load resilience setup with 3dB splitters. Under EUROfusion prospective research and development, in-port ICRF antenna concept for EU-DEMO with 8 quadruplets (4x toroidal by 2x poloidal) is considered to deliver 16.7 MW (3 antennas yielding 50 MW). Areas around the equatorial port and cut-ins in breeding blankets are used, with emphasis on [0;π;π;0] optimization. High-resolution RAPLICASOL calculations with full ne profile (without imposing a minimum ne value) shed light on field distribution with propagative slow wave in detailed antenna geometry

SOL RF physics modelling in Europe, in support of ICRF experiments

A European project was undertaken to improve the available SOL ICRF physics simulation tools and confront them with measurements. This paper first reviews code upgrades within the project. Using the multi-physics finite element solver COMSOL, the SSWICH code couples RF full-wave propagation with DC plasma biasing over “antenna-scale” 2D (toroidal/radial) domains, via non-linear RF and DC sheath boundary conditions (SBCs) applied at shaped plasma-facing boundaries. For the different modules and associated SBCs, more elaborate basic research in RF-sheath physics, SOL turbulent transport and applied mathematics, generally over smaller spatial scales, guides code improvement. The available simulation tools were applied to interpret experimental observations on various tokamaks. We focus on robust qualitative results common to several devices: the spatial distribution of RF-induced DC bias; left-right asymmetries over strap power unbalance; parametric dependence and antenna electrical tuning; DC SOL biasing far from the antennas, and RF-induced density modifications. From these results we try to identify the relevant physical ingredients necessary to reproduce the measurements, e.g. accurate radiated field maps from 3D antenna codes, spatial proximity effects from wave evanescence in the near RF field, or DC current transport. Pending issues towards quantitative predictions are also outlined

Perspectives on Preparedness for Chemical, Biological, Radiological, and Nuclear Threats in the Middle East and North Africa Region: Application of Artificial Intelligence Techniques

Over the past 3 decades, the diversity of ethnic, religious, and political backgrounds worldwide, particularly in countries of the Middle East and North Africa (MENA), has led to an increase in the number of intercountry conflicts and terrorist attacks, sometimes involving chemical and biological agents. This warrants moving toward a collaborative approach to strengthening preparedness in the region. In disaster medicine, artificial intelligence techniques have been increasingly utilized to allow a thorough analysis by revealing unseen patterns. In this study, the authors used text mining and machine learning techniques to analyze open-ended feedback from multidisciplinary experts in disaster medicine regarding the MENA region's preparedness for chemical, biological, radiological, and nuclear (CBRN) risks. Open-ended feedback from 29 international experts in disaster medicine, selected based on their organizational roles and contributions to the academic field, was collected using a modified interview method between October and December 2022. Machine learning clustering algorithms, natural language processing, and sentiment analysis were used to analyze the data gathered using R language accessed through the RStudio environment. Findings revealed negative and fearful sentiments about a lack of accessibility to preparedness information, as well as positive sentiments toward CBRN preparedness concepts raised by the modified interview method. The artificial intelligence analysis techniques revealed a common consensus among experts about the importance of having accessible and effective plans and improved health sector preparedness in MENA, especially for potential chemical and biological incidents. Findings from this study can inform policymakers in the region to converge their efforts to build collaborative initiatives to strengthen CBRN preparedness capabilities in the healthcare sector

Conception et opération d'antennes aux fréquences cyclotronique ionique et hybride basse pour les réacteurs à fusion nucléaire

Cette thèse fournit en premier lieu une brève introduction à la fusion nucléaire par confinement magnétique et aux tokamaks. Elle explique la nécessité de disposer de systèmes électromagnétiques aux fréquences cylctronique ionique (ICRF) et hybride basse (LHRF) pour le chauffage du plasma et la génération de courant. En second lieu les conditions à satisfaire afin d’assurer une propagation de l'onde plasma et une résonance onde-particules sont définies. Le solveur de réseaux hyperfréquences SIDON, développé pour cette thèse, est ensuite présenté. La thèse aborde ensuite les types d'antennes ICRF et l'adaptation d'impédance des réseaux de boucles rayonnantes. Les antennes ICRF de WEST sont présentées en détail et des simulations faites avec SIDON de scénarios d'adaptation d'impédance sont discutées. La thèse discute d’un banc de test faible puissance (milliwatt) développé pour les antennes ICRF de WEST ainsi que la caractérisation à faible puissance de la première d’entre elles. De plus, des expériences à forte puissance (mégawatt) avec l'antenne ITER-Like Antenna de JET sont discutées. Les antennes LHRF sont ensuite abordées ainsi que la modélisation numérique du couplage de réseaux phasés de guide d'ondes au plasma. La conception d'ASTARTE-LP et de son circuit d’excitation est discutée. ASTARTE-LP est un prototype faible puissance (milliwatt) d’une antenne basée sur le concept de guides à fentes et qui a été conçu pour être testé sur COMPASS. Enfin, la validation expérimentale d'ASTARTE-LP et de son circuit d’excitation avant les expériences sur COMPASS, ainsi que les expériences sur COMPASS, sont discutées.The thesis provides at first a brief introduction to magnetic nuclear fusion and tokamaks. It explains the need for auxiliary plasma heating and current-drive electromagnetic systems at the Ion Cyclotron and Lower Hybrid Range of Frequencies (ICRF and LHRF). The thesis then sets antenna specifications that allow satisfying proper plasma wave propagation and proper wave-particle resonance. The Radio Frequency (RF) network solver SIDON developed for this thesis is then presented. The thesis then discusses the different types of ICRF antennas and details the challenges of the impedance matching in ICRF arrays of straps. WEST ICRF launchers are discussed in great detail and simulations of impedance matching scenarios for these launchers using SIDON are reported. The thesis reports on the low-power (milliwatt range) testbed that has been developed for WEST ICRF launchers, as well as the low-power tests of the first one among them. Furthermore, high power (megawatt range) experiments on plasma with the JET ICRF ITER-Like Antenna are reported. The thesis then provides an overview about existing LHRF antennas and discusses the numerical modeling of the coupling of waveguide phased arrays to the plasma. The RF design of ASTARTE-LP and its feeding circuit is discussed. ASTARTE-LP is a low-power (milliwatt range) prototype LHRF antenna based on the Slotted Waveguide Antenna concept that has been designed and built to perform proof of principle experiments on the COMPASS tokamak. The experimental validation of ASTARTE-LP and its feeding circuit before the experiments on COMPASS, as well as the experiments performed on COMPASS plasmas are reported

Lower Hybrid Range Cold Magnetized Plasma Modelling in ANSYS HFSS

International audienceThe coupling between cold magnetized plasmas with Lower Hybrid Resonance Frequency antennas is generally addressed using specifically developed codes. These antenna coupling codes often approximate the plasma to a surface impedance described by a 1D half infinite models and antennas either with simplified 2D dimensions or from 3D CAD models conversion. Such approaches add an additional steps of model approximation/conversion which is not convenient to rapidly assess impact of geometry changes on coupling performances. The coupling calculation of Lower Hybrid Resonance Frequency antennas are performed using ANSYS HFSS and successfully benchmarked with the fast coupling codes ALOHA on inhomogeneous cold magnetized plasmas. Good agreements are obtained when the boundary conditions in the full-wave modelling are properly handled. Practical advices and limitations are given in order to define correctly these boundary conditions and insure correct results

Spatial proximity effects on the excitation of Sheath RF Voltages by evanescent Slow Waves in the Ion Cyclotron Range of Frequencies

International audienceWe investigate theoretically how sheath radio-frequency (RF) oscillations relate to the spatial structure of the near RF parallel electric field E∥ emitted by ion cyclotron (IC) wave launchers. We use a simple model of slow wave (SW) evanescence coupled with direct current (DC) plasma biasing via sheath boundary conditions in a 3D parallelepiped filled with homogeneous cold magnetized plasma. Within a ‘wide-sheath’ asymptotic regime, valid for large-amplitude near RF fields, the RF part of this simple RF + DC model becomes linear: the sheath oscillating voltage VRF at open field line boundaries can be re-expressed as a linear combination of individual contributions by every emitting point in the input field map. SW evanescence makes individual contributions all the larger as the wave emission point is located closer to the sheath walls. The decay of |VRF| with the emission point/sheath poloidal distance involves the transverse SW evanescence length and the radial protrusion depth of lateral boundaries. The decay of |VRF| with the emitter/sheath parallel distance is quantified as a function of the parallel SW evanescence length and the parallel connection length of open magnetic field lines. For realistic geometries and target SOL plasmas, poloidal decay occursover a few centimeters. Typical parallel decay lengths for |VRF| are found to be smaller than ICantenna parallel extension. Oscillating sheath voltages at IC antenna side limiters are thereforemainly sensitive to E∥ emission by active or passive conducting elements near these limiters,as suggested by recent experimental observations. Parallel proximity effects could also explainwhy sheath oscillations persist with antisymmetric strap toroidal phasing, despite the parallelantisymmetry of the radiated field map. They could finally justify current attempts at reducingthe RF fields induced near antenna boxes to attenuate sheath oscillations in their vicinit