Sur les champs magnétiques pulsés crowbar. I. Caractéristiques géométriques et électriques des bobines en cuivre

Abstract

2014 Un champ pulsé est défini par le champ crête B0, l'énergie magnétique W et le rayon intérieur a1 des bobines. Nous proposons un ensemble de formules qui, pour chaque couple w = W/2,5 a31 B20 et 0393 = diamètre extérieur/longueur des bobines, donnent : l'« épaisseur » de chaque bobine, leur constante de temps, l'homogénéïté du champ magnétique, la température du bobinage à la fin d'une impulsion crowbar. Nous montrons, que pour chaque champ pulsé, c'est dans la bobine 0393 = 1,36, que les contraintes magnétiques de coeur sont minimales. Nous analysons le rendement magnétique en prenant en compte l'échauffement adiabatique du bobinage. A chaque étape du texte, apparaît l'intérêt des bobines très épaisses.Abstract. 2014 A pulsed magnetic field is characterized by the peak value B0, by the magnetic energy W and by the inner coil radius a1. We propose a set of formulae giving for any values of w = W /(2.5 a31 B20) and 0393 (outer diameter/

Switching of Molecular Spin States in Inorganic Complexes by Temperature, Pressure, Magnetic Field and Light: Towards Molecular Devices

“…Keeping in mind that (i) a magnetic field stabilises the highest spin‐state of the molecule through the Zeeman effect, (ii) the spin crossover phenomenon is a dynamic process and (iii) it is possible to generate high pulsed magnetic fields21 (LNCMP/CNRS, Toulouse, France: 32 Tesla in 2000 and 60 Tesla currently), the idea of applying a pulsed magnetic field in the hysteresis loop was developed.…”

The Spin Crossover Phenomenon Under High Magnetic Field

“…The pulsed field facility at LNCMP (Toulouse) [34] produces fields up to 60 T with a pulse duration in the one second range [35], sometimes described as quasi-static.…”

“…Pulsed magnetic fields up to 32 T were generated by the discharge (up to 1.25 MJ) of a capacitor bank (25,000 mF) into a resistive copper coil immersed in liquid nitrogen. The wave form of the increasing field is a quarter of a sine wave and the maximum is reached in 75 ms, the magnetic field then decreases to 0 in 1.3 s following an exponential law due to crowbar diodes [35] inserted in the circuit, see Fig. 1.…”

Development of reliable 70 T pulsed magnets

“…The pulse shape is a damped sine wave distorted by the heating of the coil. It is common practice to connect a 'crowbar' circuit, consisting of a resistor and a diode, in parallel to the capacitor bank [3]. The 1 Present address: Forschungszentrum Rossendorf e.V., Postfach 510119, D-01314, Dresden, Germany.…”