Search results for "asma"
showing 10 items of 4204 documents
Confirmation of the topology of the Wendelstein 7-X magnetic field to better than 1:100,000
2016
Fusion energy research has in the past 40 years focused primarily on the tokamak concept, but recent advances in plasma theory and computational power have led to renewed interest in stellarators. The largest and most sophisticated stellarator in the world, Wendelstein 7-X (W7-X), has just started operation, with the aim to show that the earlier weaknesses of this concept have been addressed successfully, and that the intrinsic advantages of the concept persist, also at plasma parameters approaching those of a future fusion power plant. Here we show the first physics results, obtained before plasma operation: that the carefully tailored topology of nested magnetic surfaces needed for good c…
Modelling of combined ICRF and NBI heating in JET hybrid plasmas
2017
During the 2015-2016 JET campaigns many efforts have been devoted to the exploration of high performance plasma scenarios envisaged for ITER operation. In this paper we model the combined ICRF+NBI heating in selected key hybrid discharges using PION. The antenna frequency was tuned to match the cyclotron frequency of minority hydrogen (H) at the center of the tokamak coinciding with the second harmonic cyclotron resonance of deuterium. The modelling takes into account the synergy between ICRF and NBI heating through the second harmonic cyclotron resonance of deuterium beam ions which allows us to assess its impact on the neutron rate RNT. We evaluate the influence of H concentration which w…
The Role of Combined ICRF and NBI Heating in JET Hybrid Plasmas in Quest for High D-T Fusion Yield
2017
Combined ICRF and NBI heating played a key role in achieving the world-record fusion yield in the first deuterium-tritium campaign at the JET tokamak in 1997. The current plans for JET include new experiments with deuterium-tritium (D-T) plasmas with more ITER-like conditions given the recently installed ITER-like wall (ILW). In the 2015-2016 campaigns, significant efforts have been devoted to the development of high-performance plasma scenarios compatible with ILW in preparation of the forthcoming D-T campaign. Good progress was made in both the inductive (baseline) and the hybrid scenario: a new record JET ILW fusion yield with a significantly extended duration of the high-performance pha…
Conceptual Design and Modeling of the Toroidal Field Coils Circuit of DTT
2020
Italian Divertor Tokamak Test (DTT) facility is part of the general European programme on the fusion research. Its specific role is to cover the gap on the power exhaust for the future DEMOstration power plant (DEMO). This tokamak will be built and installed in Italy at Frascati ENEA laboratories. The paper describes the Toroidal Field (TF) coils circuit powered by a TF power supply that feeds in series 18 toroidal superconducting magnets and the development of three software models in order to validate the adopted technical solutions in term of maximum voltage and maximum current stress on each power device/component, due to both the operating and fault conditions, and across TF coils.
Progress of the conceptual design of the European DEMO breeding blanket, tritium extraction and coolant purification systems
2020
Abstract In the frame of the EUROfusion consortium activities the Helium Cooled Pebble Bed (HCPB) and the Water Cooled Lithium Lead (WCLL) concepts are being developed as possible candidates to become driver Breeding Blanket (BB) for the EU DEMO, which aims at the tritium self-sufficiency and net electricity production. The two BB design options encompass water or helium as coolants and solid ceramic with beryllium/beryllides or PbLi as tritium breeder and neutron multipliers. The BB segments have evolved towards a more stable conceptual design taking into account multiple feasibility aspects and requirements imposed by interfacing systems. Possible solutions to improve shielding capabiliti…
Status of EU DEMO heat transport and power conversion systems
2018
Abstract DEMO in Europe is considered to be the nearest-term reactor design to follow ITER and capable of demonstrating production of electricity, operating with a closed fuel-cycle and to be a facilitating machine between ITER and a commercial reactor. The aim of this paper is to show the design progress of the complex system’s “chain” devoted to the extraction of the plasma generated pulsed thermal power and its conversion into electricity delivered to the grid, including the Primary Heat Transport System (PHTS), the Power Conversion System (PCS) and the Intermediate Heat Transport System (IHTS) – provided by an Energy Storage System (ESS) – in between PHTS and PCS, which is introduced fo…
Tomographic diagnostics of high-frequency electrodeless lamps in argon–mercury mixtures
2006
Tomographic reconstruction of spatial profiles of the mercury atom density in the excited state 7 3S1 in high-frequency electrodeless lamps (HFELs) has been performed. The measurements of the Hg 546.1 nm line emission intensity have been made for the HFELs in argon–mercury mixture depending on the operation regime with different cold spot temperatures in the range 31–98 °C. The maximum entropy-based algorithm was applied for the reconstruction of local emission coefficients from the integrated intensities. The emission coefficients are directly related to the local values of the mercury atom density in the excited state 7 3S1, the upper state of the 546.1 nm transition. Such an investigatio…
Precise measurement of the top quark mass in dilepton decays using optimized neutrino weighting
2016
We measure the top quark mass in dilepton final states of top-antitop events in proton-antiproton collisions at sqrt(s) = 1.96 TeV, using data corresponding to an integrated luminosity of 9.7 fb^-1 at the Fermilab Tevatron Collider. The analysis features a comprehensive optimization of the neutrino weighting method to minimize the statistical uncertainties. We also improve the calibration of jet energies using the calibration determined in top-antitop to lepton+jets events, which reduces the otherwise limiting systematic uncertainty from the jet energy scale. The measured top quark mass is mt = 173.32 +/- 1.36(stat) +/- 0.85(syst) GeV.
Whispering gallery mode resonator sensors referenced to saturated absorption lines in rubidium atoms and a fs frequency comb
2019
Optical Whispering Gallery Mode Resonators (WGMR) can be produced by many methods, for example, by flame melting of silica fibers [1], by polishing of crystals [2], by optical lithography, by solidifying transparent materials, or using commercially available microspheres. They confine light by the total internal reflection and do not need mirror coatings. A part of radiation is traveling outside the WGMR as an evanescent wave and it is used for sensing applications. WGMRs are becoming increasingly popular as biosensors [3] when their surface is covered with antibodies to provide selectivity. Advantage is that light circulates in the resonator and interacts many times with a few molecules at…
Mechanical, thermal and electrical properties of nanostructured CNTs/SiC composites
2018
International audience; Dense SiC-based nanostructured composites reinforced by well-distributed carbon nanotubes (CNTs) were elaborated for the first time by spark plasma sintering (SPS) without sintering additive. Microstructures of materials containing different amounts of CNTs – up to 8.0 vol% – were correlated with their mechanical, electrical and thermal properties. A continuous decrease of the SiC grain size was observed when the amount of CNT was increased, while the evolution of density showed a different behavior that could be explained by the particular combination of SPS technique with the electrical resistivity evolution of the green bodies. Optimal effect of CNTs addition on h…