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A design modification to an existing 3D-trenched pixel detector is proposed, aimed at animproved fabrication yield. The device concept is studied and its performance is evaluatedby TCAD simulations, in comparison to the existing one. Although the modified designfeatures a less uniform electric field distribution, it is still expected to yield a very good timingperformance and high radiation tolerance, also exploiting charge multiplication effects.

Industrial structure are exposed to microstructural changes caused by fatigue cracking, corrosion and thermal aging. Generally, a hidden crack is very dangerous because it is difficult to detect by Non- Destructive Evaluation (NDE) techniques. This paper presents a new approach to estimate the hidden cracks dimensions inside a stainless steel plate based on the EMAT signal. The received signal by EMAT is simulated using the Finite Element Method (FEM). Then, the identification of the hidden crack sizes is performed via the combination of two techniques; the first one is the Time-of-Flight (ToF) technique which was applied to estimate the crack height by the evaluation of the difference between the ToF of the healthy form and the defective form. Then, the crack width is estimated by the solution of the inverse problem from the received signal based on a meta-heuristic algorithm called Teaching learning Based optimization (TLBO). The obtained results illustrate the sensitivity of the EMAT sensor to the variation of the crack sizes. Moreover, the quantitative evaluation of the cracks dimensions, show clearly the efficiency and reliability of the adopted approache.

In this letter, a multifunction aperture array is proposed for ultrawideband (UWB) scanning and polarization reconfiguration. The UWB array consisted of linearly polarized elements is capable of operating in four polarization modes (+45° linear polarization (LP), -45° linear polarization, left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP)). This work involves two essential techniques: (a) A new beam-scanning UWB array synthesis approach. An iterative convex optimization strategy is utilized to determine the element locations and obtain the minimum sidelobe level (SLL) for multiple patterns. (b) The polarization reconfigurable technique for beam-scannable arrays. In this part, a sequential rotation and excitation compensation (SR-EC) technique provides polarization reconfiguration for a beam-scannable array consisting of linearly polarized elements. A beam-scanning UWB array is designed by using the proposed UWB array synthesis approach and the SR-EC polarization reconfigurable technique. The Feko numerical result shows 0°-60° beam peak steering, a 4:1 bandwidth (1-4 GHz), and fourpolarization reconfigurability.

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A design modification to an existing border termination for active-edge planar radiation detectors is proposed, which enables a dead area reduction and a much larger breakdown voltage to be achieved, with a minor increase in the fabrication complexity. ‘Technology Computer-Aided Design’ simulations allowed the device performance of different variants of the proposed structure to be investigated also in comparison with the existing one. Among considered designs, the new border terminations with 2(3) guard rings, featuring a dead area at the edge of ∼90(120) μm, can withstand more than 375(500) V for all oxide charge density values up to 3 × 1012 cm−2. These characteristics make them appealing for X-ray imaging applications at free-electron laser facilities.

Small-pitch, thin 3D Si sensors have been developed for the ATLAS and CMS experiment upgrades at the High Luminosity LHC. The pixel sizes are 50 × 50 µm2 with 1 readout column, and 25 × 100 µm2 with 1 or 2 readout columns (1E and 2E). Owing to the small inter-electrode distance, ranging from ∼28 µm to ∼51 µm in the considered layouts, these devices are expected to be extremely radiation hard. TCAD simulations by Synopsys Sentaurus, incorporating advanced radiation damage models, have been used for the design/optimization of these new 3D pixel sensors. In this study, we have compared the accuracy of different bulk damage models in predicting the signal efficiency of small-pitch 3D sensors irradiated at large fluences and its evolution with the bias voltage at different positions within the 3D cell. Selected simulation results will be reported in comparison to experimental data.

Industrial equipment can be exposed to various types of damage during their long exploitation in harsh environments which might lead to corrosion cracking. Typically, a hidden crack is very dangerous since it is difficult to be detected by Non-Destructive Testing (NDT) techniques. Moreover, the integrity requirements of metallic structures cannot be satisfied by simply detecting the existence of cracks. However, the quantitative description of the cracks is still an issue that should be solved. This paper introduces a new approach to estimate the dimensions of hidden cracks inside a stainless steel plate based on Shear Vertical (SV) waves generated by an Electromagnetic Acoustic Transducer (EMAT). The Finite Elements Method (FEM) has been used to model the acquired signal by EMAT. Then, the characterization of hidden cracks is carried out by combining two methods; Time-of-Flight (ToF) technique that has been used to evaluate the crack height, and the Partial Least Square Regression (PLSR) method that has been used to estimate the crack width. The obtained results demonstrate the efficiency and the reliability of the adopted approach concerning the quantitative evaluation of the crack dimensions.

Applications at the High Luminosity LHC (HL-LHC) have required the development of a new generation of 3D pixel sensors with increased pixel granularity, extreme radiation hardness and low material budget. To this purpose, new 3D pixels have small pitch (e.g., 50×50 or 25×100 μm2) and reduced active thickness (∼100 μm). Owing to the small inter-electrode spacing (∼28 μm in the most aggressive designs). These 3D pixels are expected to be radiation hard even after irradiation at the hadron fluences. Indeed, they are of interest for the innermost tracking layers of ATLAS and CMS (∼2×1016 neq cm−2), and beyond. In order to estimate the charge collection efficiency (CCE) after irradiation, TCAD simulations can be conveniently used, providing useful information for the optimization of sensor design and fabrication technology. Within the AIDA-2020 project, with reference to the new single-sided 3D technology from FBK (Trento, Italy), we have simulated the CCE of pixel sensors with different inter-electrode spacing irradiated at different fluences. For these simulations, a 2D domain was used, consisting of a horizontal slice taken at half the depth of a 3D sensor. Simulations consider the hit of a minimum ionizing particle, described by the Heavy Ion model at different points within the active area. In addition, bulk radiation damage is accounted by using advanced deep-level trap models. This paper reports a comprehensive description of the simulation results based on a radiation model validated by comparison to experimental results from n-in-p strip detectors at 248 K and 900 V bias.

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International audience; This paper presents the use of the Least Square Support Vector Machines (LS-SVM) technique, combined with the Finite Element Method (FEM), to characterize small cracks in order to get a fast non-destructive inspection. The LS-SVM is a statistical learning method that has good generalization capability and learning performance. LS-SVM trained model is proposed to predict crack sizing using experimental signals acquired from an Eddy Current (EC) sensor. The FEM is used to create the data set required to train this model. The performance of LS-SVM model depends on a careful setting of its associated hyper-parameters. Different tuning techniques for optimizing the LS-SVM hyper-parameters are studied: Electromagnetism-Like Mechanism (EM), Opposition Based Electromagnetism-Like Mechanism (OBEM) and Teaching Learning Based Optimization (TLBO). Results show that TLBO algorithm provides a good compromise between accuracy and computational cost.

International audience; Eddy Current Testing (ECT) is a fast and effective method for detecting and sizing most of the default in conducting materials. The size estimation of an unknown defect from the measurement of the impedance variations is an important technique in industrial area. This paper considers to solve this problem by the novel combination of the Least Square Support Vector Machines (LS-SVM) and Finite Element Method (FEM). The FEM is used to modelling the eddy current sensor. In this context, Comsol Multiphysics resolution using a 3D electromagnetic formulation have been considered to create a database required to train the LS-SVM. Several method exist to find the LS-SVM parameters. Electromagnetism-like Mechanism (EM) algorithm is proposed. A good agreement is obtained between the numerical results and the experimental measure.

Eddy current (EC) sensors are used for non-destructive testing since they are able to probe conductive materials. Despite being a conventional technique for defect detection and localization, the main weakness of this technique is that defect characterization, of the exact determination of the shape and dimension, is still a question to be answered. In this work, we demonstrate the capability of small crack sizing using signals acquired from an EC sensor. We report our effort to develop a systematic approach to estimate the size of rectangular and thin defects (length and depth) in a conductive plate. The achieved approach by the novel combination of a finite element method (FEM) with a statistical learning method is called least square support vector machines (LS-SVM). First, we use the FEM to design the forward problem. Next, an algorithm is used to find an adaptive database. Finally, the LS-SVM is used to solve the inverse problems, creating polynomial functions able to approximate the correlation between the crack dimension and the signal picked up from the EC sensor. Several methods are used to find the parameters of the LS-SVM. In this study, the particle swarm optimization (PSO) and genetic algorithm (GA) are proposed for tuning the LS-SVM. The results of the design and the inversions were compared to both simulated and experimental data, with accuracy experimentally verified. These suggested results prove the applicability of the presented approach.

International audience; This paper is concerned with the characterization methodologies of defects in conducting materials by an Electromagnetic Acoustic Transducer (EMAT) testing system. It has been developed to create a virtual environment for Non-Destructive Testing (NDT) before implementing it in real, to study the change effect on the defect geometry at the signal received. EMAT is a new technology, which provides a noncontact process of testing materials compared to ultrasonic testing technique. This work is based on the simulation of two-dimensional numerical model, using Finite Element Method, (FEM) like a simulator model forward analysis, which includes the calculation of induced eddy current, the Lorentz force, and mechanical displacement inside conducting material. Results obtained shows that the model is capable of detecting the depth, the width and the location of the surface defect in an Aluminum material, using the mechanical displacement amplitude.

International audience