Concept

Dynamo terrestre

Publications associées (26)

Magnetic Field Spreading from Stellar and Galactic Dynamos into the Exterior

The exteriors of stellar and galactic dynamos are usually modeled as current-free potential fields. A more realistic description might instead be that of a force-free magnetic field. Here, we suggest that, in the absence of outflows, neither of these reflects the actual behavior when the magnetic field spreads diffusively into a more poorly conducting turbulent exterior outside dynamo. In particular, we explain why the usual ordering, in which the dipole magnetic field is the most slowly decaying one, is al

American Astronomical Society2026

Inducing Ferroquadrupolar Order with Applied Magnetic Field in TbPO4

In this work, we demonstrate a remarkable field-induced ferroquadrupolar phase emanating from the magnetoelastic coupling. Using synchrotron x-ray and neutron diffraction, heat capacity measurements, as well as mean-field modeling, we show that above the critical magnetic field, ferroquadrupolar O2-2 order is stabilized as the main order parameter, in competition with the field-induced magnetic polarization. This is revealed by a severe lattice distortion and the suppression of antiferromagnetic ordering of

2026

Xenon Dynamic Nuclear Polarization: from Spin Dynamics to In-Vivo Applications

Hyperpolarization in Magnetic Resonance Imaging addresses the inherently low sensitivity of the imaging modality. The range of hyperpolarization techniques has drastically improved in the last 25 years, exploring a range of functionality including metabolic, perfusion and ventilation substrates. Two central hyperpolarization techniques are Spin Exchange Optical Pumping (SEOP) and Dynamic Nuclear Polarization (DNP), whereas the first is applied while the substrate is in a gaseous state, the latter hyperpolar

EPFL2026

Complex magnetoelectric effect in multiferroic composites: the case of PFN- PT/(Co,Ni)Fe2O4

We report a systematic study of the magnetoelectric (ME) voltage coefficient as a complex quantity in the particulate composite of ferroelectric solid solution 0.94Pb(Fe1/2N1/2)O-3-0.06PbTiO(3)(PFN-PT) with CoFe2O4(CFO) and NiFe2O4 (NFO) ferrites. The resu ...

2019

Direct enhancement of nitrogen-15 targets at high-field by fast ADAPT-SABRE

Gabriele Stevanato

Signal Amplification by Reversible Exchange (SABRE) is an attractive nuclear spin hyperpolarization technique capable of huge sensitivity enhancement in nuclear magnetic resonance (NMR) detection. The resonance condition of SABRE hyperpolarization depends ...

Academic Press Inc - Elsevier Science2017

Conceptual design of the EU DEMO EC-system: main developments and R&D achievements

Stefano Alberti, Minh Quang Tran, Falk Hans Braunmüller, Ioannis Pagonakis

For the development of a DEMOnstration Fusion Power Plant the design of auxiliary heating systems is a key activity in order to achieve controlled burning plasma. The present heating mix considers electron cyclotron resonance heating (ECRH), neutral beam i ...

IOP Publishing Ltd2017

Overview of Performance Test of Korean CICCs for ITER TF Magnet

Pierluigi Bruzzone, Boris Stepanov

The Korean Domestic Agency (KODA) for the International Thermonuclear Experimental Reactor (ITER) project has taken the responsibility of the procurement of cable-in-conduit conductors for the ITER toroidal field magnet. While procuring 27 conductor unit l ...

IEEE Institute of Electrical and Electronics Engineers2016

Guiding-centre transformation of the radiation-reaction force in a non-uniform magnetic field

Joan Decker

In this paper, we present the guiding-centre transformation of the radiation reaction force of a classical point charge travelling in a non-uniform magnetic field. The transformation is valid as long as the gyroradius of the charged particles is much small ...

Cambridge University Press2015

Examination of Nb3Sn Conductors for ITER Central Solenoids

Pierluigi Bruzzone, Kamil Sedlák, Boris Stepanov

The performance of two Nb3Sn conductors for the ITER central solenoids was tested. The current sharing temperatures (T-cs) were measured over 17 050 electromagnetic cycles, including four thermal cycles between 4.2 K and room temperature. T-cs declined alm ...

IEEE Institute of Electrical and Electronics Engineers2013

Tokamak coordinate conventions: COCOS

Olivier Sauter

Dealing with electromagnetic fields, in particular current and related magnetic fields, yields "natural" physical vector relations in 3-D. However, when it comes to choosing local coordinate systems, the "usual" right-handed systems are not necessarily the ...

Elsevier Science Bv2013

Examination of Japanese Mass-Produced Nb3Sn Conductors for ITER Toroidal Field Coils

Pierluigi Bruzzone, Boris Stepanov

The performances of six Nb3Sn conductors for the ITER Toroidal Field coils were tested. Four of them showed similar degradation rates of their current sharing temperatures T-cs over 1,000 electromagnetic cycles. By contrast, two of them showed sharp T-cs d ...

IEEE-Inst Electrical Electronics Engineers Inc2012

Self-Consistent ICRH Distribution Functions and Equilibria in Magnetically Confined Plasmas

Martin Jucker

The deployment of high power radio frequency waves in the ion cyclotron range (ICRF) constitutes an important operational facility in many plasma devices, including ITER. Any charged particle describes a helical motion around a given magnetic field line, t ...

EPFL2010

Numerical modelling of light emission and propagation in (organic) LEDs with the Green's tensor

The accepted model for light emission and propagation in organic LEDs (OLED) which consists of several optically thin functional layers deposited on a thick substrate is a classical dipole located in the emitting layer. The propagation of the emitted light is commonly described by a Fourier expansion of the dipole field into plane waves which represent the various radiating and bound modes of the layered structure in k-space. To calculate the electric and magnetic fields inside and outside the LED an integr

Spie-Int Soc Optical Engineering, Po Box 10, Bellingham, Wa 98227-0010 Usa2004

Noncollinear magnetism in liquid oxygen: A first-principles molecular dynamics study

Alfredo Pasquarello

We perform first-principles molecular dynamics of liquid oxygen in which the magnetic structure evolves according to a generalized density-functional scheme allowing for noncollinear spin configurations. We investigate both structural correlations between the orientations of the molecular axes and magnetic correlations between the orientations of the molecular magnetic moments, demonstrating a clear relation between the local molecular configuration and the relative magnetic arrangement. The nuclear structu

American Physical Society2004

On the estimation of lightning peak currents from measured fields using lightning location systems

Farhad Rachidi-Haeri, José-Luis Bermudez

Although, due to the high variability of key parameters such as the return-stroke speed, it is impossible to determine the lightning current accurately from the remotely measured electric or magnetic field for a given event, we show in this paper that, for an assumed return-stroke model, the statistical estimation (e.g. in terms of mean values and standard deviations) is possible. We show additionally that for the transmission line (TL) model, the equation permitting to infer the mean value of the return-st

2004

Modelling the magnetic field effects in a high-Tc superconducting transformer

Bertrand Dutoit, Svetlomir Stavrev

This paper describes quantitatively the magnetic field inside the windings of a HTS transformer. The results are obtained by means of finite element method simulations, using the electromagnetic software package Flux2D. The transformer design has been made by ŠKODA in the European project BIG-POWA. The ratings of the transformer are U1 = 400 V, I1 = 47 A, U2 = 133 V, I2 = 140 A (rms values). The magnetic field in the superconducting windings has been calculated in the steady state regime at 50 Hz. It is non

2003

Current and electromagnetic field associated with lightning-return strokes to tall towers

Farhad Rachidi-Haeri

In this paper, an analysis of electric and magnetic fields radiated by lightning first and subsequent return strokes to tall towers is presented. The contributions of the various components of the fields, namely, static, induction, and radiation for the electric field, and induction and radiation for the magnetic field are illustrated and discussed. It is shown in particular that the presence of a tower tends, in general, to increase substantially the electric and magnetic field peaks and their derivatives.

2001

Neoclassical conductivity and bootstrap current formulas for general axisymmetric equilibria and arbitrary collisionality regime

Olivier Sauter, Clemente Angioni

Expressions for the neoclassical resistivity and the bootstrap current coefficients in terms of aspect ratio and collisionality are widely used in simulating toroidal axisymmetric equilibria and transport evolution. The formulas used are in most cases based on works done 15-20 years ago, where the results have been obtained for large aspect ratio, small or very large collisionality, or with a reduced collision operator. The best expressions to date and to our knowledge are due to Hirshman [S. P. Hirshman, P

1999

A new compact 2D planar fluxgate sensor with amorphous metal core

Radivoje Popovic, Pavel Kejik

A new compact 2D planar fluxgate sensor using a ferromagnetic amorphous metal core is described. The fluxgate sensor consists of two orthogonal planar coils and an amorphous magnetic ring core mounted on a PCB substrate. Each planar coil is used alternatively as excitation or as pick-up coil. An electronic interface drives alternatively the two coils and performs a feedback on each sensing coil in order to compensate for the measured magnetic field. The sensing element has a magnetic detectivity of 40nT for

1998

Dynamics of charged excitons in GaAs quantum wells under high magnetic field

Benoît Marie Joseph Deveaud, Jean-Daniel Ganière, Victoria Ciulin, Stefan Haacke

We report on time-resolved photoluminescence studies of charged and neutral excitons in a modulation doped GaAs quantum well under resonant excitation and high magnetic field. The radiative lifetime of the charged exciton is rather short, 60 ps at zero held, and is found to increase by a factor of similar to 2 up to 7 T. The short lifetimes suggest that, under magnetic field, the exciton bound in the trion is delocalized. (C) 1998 Elsevier Science B.V. All rights reserved.

1998

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Publications associées (26)

Neoclassical conductivity and bootstrap current formulas for general axisymmetric equilibria and arbitrary collisionality regime

Olivier Sauter, Clemente Angioni

1999

A new compact 2D planar fluxgate sensor with amorphous metal core

Radivoje Popovic, Pavel Kejik

1998

Dynamics of charged excitons in GaAs quantum wells under high magnetic field

Benoît Marie Joseph Deveaud, Jean-Daniel Ganière, Victoria Ciulin, Stefan Haacke

1998