München 2019 – scientific programme

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GP: Fachverband Geschichte der Physik

GP 12: Technological development of tools of physics

GP 12.1: Talk

Wednesday, March 20, 2019, 16:30–17:00, HS 9

Laboratory Electromagnets (E-Ms) — •Jean-François Loude¹ and Dominique Bernard² — ¹EPFL, Lausanne, Switzerland — ²Université de Rennes 1, Rennes, France

The first iron-cored E-Ms were built by Sturgeon (1824) and Henry (1831). Their mechanical action on iron was used to lift heavy weights. Faraday discovered in 1845 the dia- and the para-magnetism of various substances and the Faraday rotation. The construction of E-Ms specially designed to investigate the properties of material samples immersed in a magnetic field began with Ruhmkorff (1848). Scientific principles were first applied in the ring-magnets of H. du Bois (1894). In 1907, the first big, water-cooled, truly modern E-M, designed by P. Weiss was installed at ETH-Zürich. Size and maximum field are limited by the materials and the scaling laws. Improvements were progressively introduced, notably in the cooling system and in the form of the pole-pieces. Size went up. A giant one (120 t) was inaugurated in 1928 at Meudon-Bellevue. Since around 1965, the cryogenic superconducting magnets offer an improvement of an order of magnitude in the maximum field of E-Ms. Numerous effects produced by magnetic fields, many of them of technological importance, were discovered by physicists working with the E-M locally at their disposal. Among them, on the atomic scale, the Kerr magneto-optical effect (1878-1878), the Hall magneto-optical effect (1879), the Zeeman effect (1897), the Meissner effect (1933), and, on the nuclear scale, the Nuclear Magnetic Resonance (E. M. Purcell 1946).