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There are three main magnet systems in Wendelstein 7-X, comprising in total 85 coils arranged in 22 independent circuits fed by steady state power supplies. The superconducting coil system creates the main magnetic field and consists of 70 coils, grouped in seven electrical circuits with ten coils each with an inductance of about one Henry. Each circuit is fed by one power supply with a maximum current...
Erosion of plasma facing materials (PFMs) during a tokamak disruption limits the lifetime and increases the need of plasma facing components (PFCs) replacement in the reactor. During disruption, energetic plasma particles deposit high heat fluxes on the PFCs. It has been shown theoretically and experimentally that the deposited energy by plasma particles vaporizes the surface of the PFMs. Besides...
JT-60SA will be provided with a set of power supply systems procured by Europe and Japan under the framework of Broader Approach Agreement. The toroidal circuit is supplied by an ac/dc thyristors converter rated for 25.7 kA in steady state, and the toroidal superconducting coils are protected by three Quench Protection Circuits (QPC) assuring fast dissipation of the stored magnetic energy of about...
Reduced activation ferritic/martensitic (RAFM) steels, whose primary composition is iron and chromium, are considered as primary candidate structural materials for fusion demo and test reactor due to its technological maturity. There are a large numbers of defects, including dislocation loops, helium clusters, voids and interfaces, existing in RAFM steels irradiated under fusion environment, which...
A fusion reactor concept is described in which a low-beta main plasma is supplied with D-T fuel, heating, and inductive energy by means of high-speed plasma rings injected from both ends. The very high plasma current is slowly built up over time using modest injection hardware.
Vacancy-type defects in Fe-2%Al2O3 (ODS-Fe) and pure Fe produced by helium ion irradiation at room temperature were investigated using positron beam Doppler broadening energy spectra (DBES). Defect profiles of the S parameter derived from DBES as a function of positron incident energy up to 20 KeV were analyzed. The S parameter values of the damaged layer for the ODS-Fe are smaller than those of pure...
Understanding the residual stress state in brazed joints is crucial for operational design and life time performance of the part in service. High magnitude residual stresses are expected in the joined materials following cooling from brazing temperatures (≈950C) due to large mismatches in material properties such as coefficient of thermal expansion and Young's modulus (E). This paper aims to further...
The affordable, robust, compact (ARC) reactor conceptual design study aims to reduce the size, cost, and complexity of a combined fusion nuclear science facility (FNSF) and demonstration fusion pilot power plant. ARC is a 200 MWe tokamak reactor with a major radius of 3.3 m, a minor radius of 1.1 m, and an on-axis magnetic field of 9.2 T. ARC is designed to use rare earth barium copper oxide (REBCO),...
Liquid metals are garnering increased attention as an alternative divertor solution to tungsten divertors. While tungsten suffers from a myriad of potentially critical issues, such as bulk erosion, melting under significant transient heat loads, and nanostructuring colloquially referred to as “fuzz”, liquid metals avoid many of these entirely. In order to implement liquid metal concepts, the interactions...
Eddy current induced electromagnetic (EM) loads during plasma events are the design driver for ITER port plug (PP) structure, diagnostic first wall (DFW), shield module (DSM) and diagnostic system supported by the PP structure. Generic models using commercial software OPERA, MAXWELL and ANSYS are developed and benchmarks are performed for global EM analysis to obtain port-specific design driving EM...
Recent experiments in ASDEX Upgrade aimed at improving the physics base for ITER and DEMO to aid the design and prepare operation. In order to increase its exhaust capabilities and operational flexibility a new bulk W divertor as well as an adjustable cryo-pump had been installed prior to the 2014 campaign. In experiments with high field side pellet injection central electron densities twice as high...
Experimental results from the National Spherical Torus Experiment (NSTX), a medium-size spherical tokamak with a compact divertor, and DIII-D, a large conventional aspect ratio tokamak, demonstrate that the snowflake (SF) divertor configuration (D.D. Ryutov, Phys. Plasmas, 14, 064502, 2007) may provide a promising solution for mitigating divertor heat loads and target plate erosion compatible with...
The Wendelstein 7-X (W7-X) stellarator experiment is scheduled to begin operation in 2015 with steady-state operation planned for 2019. During the steady-state operation, certain simulated plasma scenarios have been shown to produce heat fluxes that surpass the technological limits on the edges of the divertor target elements. To reduce the heat load on the target elements, the addition of a “scraper...
The heat loading on plasma facing components provides one of the critical design challenges for the first wall and divertors for fusion power plants. To date, design of these components has focused on steady operating conditions, but the less understood transient edge localized modes and off-normal loading conditions such as plasma disruption must also be considered. In this article, we summarize...
Systems codes are commonly employed for the analysis and conceptual design of next-step burning-plasma devices. For the helical-axis advanced stellarator (HELIAS) line a new set of systems code models have been developed to account for the stellarator-specific 3D aspects. The models have recently been implemented in the systems code PROCESS and verified with respect to different test cases.
We investigate and calculate particle orbits and the effect of particle orbits on plasma current density for nonrelativistic resonance condition in the present RF-driven divertor plasma on QUEST. We surveyed particle orbits for different values of parallel refractive index, particle initial positions and pitch angles on fundamental and second harmonic resonance conditions. We observed that for fundamental...
A small radiofrequency (RF) ion source, named NIO1 (Negative Ion Optimization, phase 1), has been recently installed at Consorzio RFX, in Padua. The NIO1 source is capable of producing about 130 mA of negative hydrogen ions accelerated at 60 kV and represents a useful test bench for negative ions source optimization. The exploitation of this device is included in the framework of the activities for...
NSTX-U research will offer new insight by studying gas assimilation efficiencies for MGI injection from different poloidal locations using identical gas injection systems. In support of this activity, an electromagnetic MGI valve has been built and tested. The valve operates by repelling a conductive disk due to eddy currents induced on it by a rapidly changing magnetic field created by a pancake...
Liquid metals are sometimes considered as an alternative material for plasma-facing components in fusion reactors and experiments. Among the liquid metals, lithium has been used in a number of experimental devices and has received significant attention. A significant question is whether liquid lithium can be used in systems requiring power exhaust as is found in typical power reactor divertors or...
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