Modelling of power exhaust in fusion plasmas

This PhD thesis deals with the thorny problem of “Modelling of power exhaust in fusion plasmas”, a challenge concerning the development of a system able to withstand the large loads expected in the fusion power plant divertor. After an introduction to fusion and to the key concepts modelling the behaviour of the plasma during plasma-surface interactions and describing the power exhaust, an overview of the state-of-the-art in the research field on power exhaust is given. A brief introduction on theoretical basis of the plasma boundary reconstruction precedes the author first contribution in the design and vertical stability analysis of plasma alternative magnetic configurations for a demonstration fusion power plant (DEMO). The second contribution concerns an assessment of the DEMO divertor target tiles lifetime in case of strike-point sweeping. This technique is one of the most promising candidate solution to the power exhaust issue but its main drawback is related to the periodical heating and cooling of the plasma facing components inducing the thermal-fatigue phenomenon. To evaluate the lifetime of the DEMO divertor target tiles, different 2D and 3D thermo-mechanical models are presented. Finally, a preliminary analysis on the wobbling technique applied to a DEMO Double Null plasma magnetic configuration is illustrated

Self-Similarity in Magnetostrictive Materials: An Experimental Point of View

Magnetostrictive behavior is characterized by a complex coupling between magnetic and mechanical quantities. While this behavior can be quite easily exploited for both actuation and sensing or energy conversion purposes, the complex hysteresis interaction between magnetization and magnetic field and mechanical stress and strain is hard to model. Nevertheless, magnetic and magnetostrictive experimental curves are quite self-similar, assuming stress as self-similarity parameter. The quantification of this concept would help modeling. Here, this concept is quantified and experimentally confirmed over different types of magnetostrictive samples

Design and Optimization of a Boost Interface for Magnetostrictive Energy Harvesting

Magnetostrictive alloys are very promising for Vibration Energy Harvesting applications to supply power to Wireless Sensor Network (WSN) and Internet of Things (IoT) devices, especially because of their intrinsic robustness. Typically, vibration energy sources are random in nature, usually providing exploitable voltages much lower than the electronic standards 1.6, 3.3 and 5 V. Therefore, a Power Electronic Interface (PEI) is needed to improve the conversion to DC output voltage from AC input over a wide range of frequencies and amplitudes. Very few or no conversion techniques are available for magnetostrictive devices, although several have been presented over the years for other smart materials, such as piezoelectrics. For example, hybrid buck–boost converters for piezoelectrics use one or more external inductors with a high-frequency switching technique. However, because of the intrinsic nature of harvesters based on magnetostrictive materials, such energy conversion techniques are proved to be neither efficient nor applicable. An improved AC–DC boost converter seems very promising for our purpose instead. The key feature is represented by the direct exploitation of the active harvester coil as a storage element of the boost circuit, without using other passive inductors as in other switching methods. Experimental tests of such a converter, driven with a real-time operating Arduino controller to detect the polarity of the input voltage, are presented with the aim to assess the potentiality of the scheme with both sinusoidal and impulse-like inputs. Simulations have been performed with LTspice, and the performance and efficiency have been compared with other energy conversion techniques

Experimental Characterization of an AC–DC Boost for Energy Harvesting Device Based on Magnetostrictive Materials

Magnetostrictive alloys hold great promise for Energy Harvesting applications due to their inherent durability. However, their implementation often results in usable voltage ranges that fall significantly below common electronic standards like 1.6, 3.3, and 5 volts. Consequently, the utilization of electronic circuits becomes essential to amplify the voltage and enhance energy conversion efficiency. Over the past few decades, numerous conversion techniques have been devised for other intelligent materials, such as piezoelectrics, some of which have even made their way into commercial products. Surprisingly, there is a dearth of specialized techniques, if not a complete absence, tailored to magnetostrictive devices. Among potential solutions, a suitable AC–DC Boost converter stands out as a highly promising candidate for addressing this challenge, but this solution has never been fully characterized. Then, this paper presents thorough experimental validations of such a converter, driven by a real-time Arduino board equipped to measure source time periods and operate under various conditions. We present several cases demonstrating the circuit’s substantial potential for enhancing energy harvesting from magnetostrictive materials

Power-Efficient Design of Large-Aperture Magnets for High-Energy Physics

Anovel and sustainability-oriented approach to the design of large-aperture iron-dominated magnets is proposed, focusing on its application to charged particle momentum detection in highenergy experimental physics. As compared to classical design techniques, a broader number of goals and constraints is taken into account, considering jointly the detection performance, the minimization of both the electrical power and magnet size, and the electromagnetic efficiency. A case study is considered for the detector magnet of a specific experiment, where the optimal design is pursued with semi-analytical tools, duly introducing the main quantities’ scaling laws in analytical form and successively validating the results with 3D numerical tools. A solution at higher energy efficiency is obtained, as compared to a more traditional design point of view. The proposed methodology can be fruitfully employed also in the design of magnets with a reduced ecological footprint in a number of other industrial and medical applications

Different presentation of bicuspid aortic valve in 169 sportsmen.

OBJECTIVE Bicuspid aortic valve (BAV) is the most common congenital cardiac anomaly (1-2%) in the general population. Aims of our study were: 1) to evaluate the different patterns of presentation of BAV; 2) to compare different BAV morphological phenotypes. METHODS Since 1986 to 2009, 169 sportsmen with BAV (mean age 22\ub110.4, range 7-67 years), were evaluated for different reasons in our Institution. Each subject underwent a thorough cardiological evaluation comprehensive of clinical examination, resting and exercise ECG, echocardiogram, 24h-Holter monitoring and, when indicated, magnetic resonance imaging of the heart and/or angio-CT of coronary arteries. RESULTS BAV was associated with cardiac pathologies/abnormalities in 46/169 (27%) sportsmen. After excluding subjects with significant cardiac pathologies (10 cases), aged 50 years (8 cases), the remaining 151 were classified in 4 groups: group 0, (22 cases, 14.6%) with an \u201calmost normal valve\u201d; group 1, (94 subjects, 62.2%) with regurgitation; group 2, (16 cases, 10.6%) with stenosis; group 3, (19 subjects, 12.6%) with isolated aortic dilation. Moreover, taking into account BAV morphology, 109 cases (72.2%) showed antero-posteriorly (AP) and 42 (27.8%) latero-laterally (LL) oriented cusps. Sportsmen with AP-BAV showed larger aortic diameter (34.7\ub15.9 vs 31.7\ub16.1) and a greater proneness to progressive dilation during follow-up (+0.04\ub10.08 vs +0.02\ub10.05 mm/year). DISCUSSION & CONCLUSION As other cardiac pathologies/abnormalities are frequently observed in sportsmen with BAV, a thorough cardiological investigation must always be carried out. Several patterns of BAV presentation exist, possibly with different outcome. Valve morphology, finally, seems to be a predictive factor for its prognosis