Cascaded multilevel inverter for vertical stabilization and radial control power supplies

This paper presents the analysis and topology selection for the power supplies of the two DTT equatorial in-vessel coils for plasma vertical stabilization and fast radial control. The physics requirements and assumptions are analyzed in order to identify the system specifications. Since the basic configuration with two independent power supply circuits is too vulnerable to fast plasma events as disruptions, a circuit configuration including both coils is introduced. Two successive solutions, with three or two power converters, are proposed to supply such a common circuit. The adopted topology, based on cascaded H-bridge converters with IGBTs, is simulated by means of a simplified circuital model, that also consider the plasma disruptions. The simulation results show that vertical stabilization and fast radial control functions can be simultaneously achieved with two identical power converters and a passive imbalance branch by using a specific current control scheme

Status and challenges for the concept design development of the EU DEMO Plant Electrical System

The EU DEMO Plant Electrical System (PES) main scopes are to supply all the plant electrical loads and to deliver to the Power Transmission Grid (PTG) the net electrical power generated. The studies on the PES during the Pre-Concept Design (PCD) Phase were mainly addressed to understand the possible issues, related to the special features both of the power generated, with respect to a power plant of the same size, and of the power to be supplied to the electrical loads. For this purpose, the approach was to start the design of the different PES components adopting technologies already utilized in fusion experiments and in Nuclear Power Plants (NPP) to verify their applicability and identify possible limits when scaled to the DEMO size and applied to the specific pulsed operating conditions. This work is not completed, however several issues have been already identified related to the pulsed operation of the turbine generator, the large amount of recirculation power, the very high peaks of active power required for the plasma formation and control, the huge reactive power demand, if thyristor converter technology was adopted to supply the superconducting coils, etc.. The paper gives an overview on the features and scope of the PES and its subsystems, on the main achievements during the Pre-Concept Design (PCD) Phase, on the challenges for the development of the conceptual design in the next framework program and on the plan to face them

Recurrent spontaneous hip dislocation in a patient with neurofibromatosis type 1: a case report

<p>Abstract</p> <p>Introduction</p> <p>Neurofibromatosis type-1 is a common genetic disorder which often affects the skeleton. Skeletal manifestations of neurofibromatosis type-1 include scoliosis, congenital pseudarthrosis of the tibia and intraosseous cystic lesions. Dislocation of the hip associated with neurofibromatosis type-1 is a rare occurrence and is underreported in the literature.</p> <p>Case presentation</p> <p>We report a case of hip dislocation resulting from an intra-articular neurofibroma in an 18-year-old Caucasian woman following minor trauma. This was originally suggested by the abnormalities on early radiographs of her pelvis and later confirmed with computed tomography and magnetic resonance imaging. Treatment was successful with skeletal traction for six weeks with no further hip dislocations at a 12-year follow-up.</p> <p>Conclusion</p> <p>This case illustrates the radiological features of this rare complication of neurofibromatosis type-1 using the modalities of plain radiograph, magnetic resonance imaging and computed tomography reconstruction. The radiological images give a clear insight into the mechanism by which neurofibromatosis type-1 leads to hip dislocation. It also demonstrates one treatment option with excellent results on long-term follow-up.</p

D-shaped configurations in FTU for testing liquid lithium limiter: Preliminary studies and experiments

The feasibility of getting "D" shaped plasma configurations in FTU, with a possible X point close to the first wall, has been investigated with the aim of achieving an H-mode regime in this machine. This regime could allow both evaluating the thermal effects on the liquid lithium limiter due to the possible Edge Localized Modes and studying the L-H transition properties in low recycling conditions due to the presence of lithium.. An alternative design for the magnetic system in FTU has been also proposed, to realize an X-point inside the plasma chamber, close to the Liquid Lithium Limiter.Preliminary experiments with elongated configurations and limited ECRH additional heating power did not allowed approaching the L-H transition but they were used to develop a proper elongation control. This controller allowed guaranteeing the vertical stability in elongated configurations despite the reduced power available for the horizontal field coils in FTU. The elongation was stably keep over 1.2, while the lithium limiter was very close to the last close flux surface. Neither limiter damages nor plasma pollution were observed in these configurations.A possible alternative connection of the poloidal field coils in FTU is here proposed, with the aim of achieving a true X-point configuration with a magnetic single null well inside the plasma chamber and strike points on the lithium limiter. A preliminary assessment of this design allowed estimating the required power supply upgrade and showed its compatibility with the existing mechanical structure and cooling system, at least for plasmas with current up to 300 kA and flat-top duration up to 4s. Keywords: FTU, Liquid lithium limiter, L-H transition, X-point, Plasma elongatio

DTT - Divertor Tokamak Test facility: A testbed for DEMO

The effective treatment of the heat and power exhaust is a critical issue in the road map to the realization of the fusion energy. In order to provide possible, reliable, well assessed and on-time answers to DEMO, the Divertor Tokamak Test facility (DTT) has been conceived and projected to be carried out and operated within the European strategy in fusion technology. This paper, based on the invited plenary talk at the 31st virtual SOFT Conference 2020, provides an overview of the DTT scientific proposal, which is deeply illustrated in the 2019 DTT Interim Design Report

Overview of the FTU results

Since the 2016 IAEA Fusion Energy Conference, FTU operations have been mainly devoted to experiments on runaway electrons and investigations into a tin liquid limiter; other experiments have involved studies of elongated plasmas and dust. The tearing mode onset in the high density regime has been studied by means of the linear resistive code MARS, and the highly collisional regimes have been investigated. New diagnostics, such as a runaway electron imaging spectroscopy system for in-flight runaway studies and a triple Cherenkov probe for the measurement of escaping electrons, have been successfully installed and tested, and new capabilities of the collective Thomson scattering and the laser induced breakdown spectroscopy diagnostics have been explored

DTT - Divertor Tokamak Test facility - Interim Design Report

The “Divertor Tokamak Test facility, DTT” is a milestone along the international program aimed at demonstrating – in the second half of this century – the feasibility of obtaining to commercial electricity from controlled thermonuclear fusion. DTT is a Tokamak conceived and designed in Italy with a broad international vision. The construction will be carried out in the ENEA Frascati site, mainly supported by national funds, complemented by EUROfusion and European incentive schemes for innovative investments. The project team includes more than 180 high-standard researchers from ENEA, CREATE, CNR, INFN, RFX and various universities. The volume, entitled DTT Interim Design Report (“Green Book” from the colour of the cover), briefly describes the status of the project, the planning of the design future activities and its organizational structure. The publication of the Green Book also provides an occasion for thorough discussions in the fusion community and a broad international collaboration on the DTT challenge

Modeling Non-Ideal Behaviors of Supercapacitors' Equivalent Capacitance

Supercapacitors can improve energy storage performances and capabilities, in particular for applications requiring high specific capacitance and high specific power. Unfortunately, supercapacitors are characterized by several non-ideal and complex behaviors that must be modeled and taken into account. One of the most relevant issue consists in the definition of the equivalent capacitance and then to the energy that can be potentially stored and practically used. This paper discusses the possible capacitance definitions and measurement methods, including the possible approaches to model the capacitance and its non-idealities