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Steady magnetic fields in Grenoble

The effects of magnetic fields namely in physics, have justified important technological efforts : first using electro-magnets and reducing their air gap to produce magnetic fields smaller than 2T- 3T, then using copper coils (Wood or Bitter) in which an efficient water cooling must eliminate the electrical losses (by Joule effect) associated to large electric currents. Continuous fields of a few telslas (R. Pauthenet) are available in Grenoble with electro-magnets built in 1950 and 1959, as well as pulsed magnetic fields reaching 30T (or even 10 times more with explosive methods) in 1960 (M. Guillot).

“Hall champs forts” in 1968

In 1962, as soon as the CNRS laboratories were built on the Grenoble-polygone area, Louis Néel conceived the project of reaching higher magnetic fields, with a large generator. In 1968, magnetic fields of 8T in 50 mm of diameter are obtained With a generator of 1.7MW (High field hall, R.Pauthenet, P. Rub and J.C. Picoche). They allow experiments at low temperatures (50 mK) obtained by adiabatic demagnetization. However, around 1970, magnetic fields reaching 15-20 T in a 30 mm diameter are produced with a 9.6 MW generator (in MIT Boston, Francis Bitter).

Klaus von Klitzing in Stokholm, 1985

The progress in the domain of dry redressors (thyristors) allow to conceive a new installation (without generator) which is built under the direction of R. Pauthenet by Jean-Claude Picoche and Pierre Rub in another building. This installation, named ‘Service National des Champs Magnétiques Intenses” in 1970 is adapted for a 10 MW power. The 5 MW initially installed allow to reach magnetic fields of 15 to 20T in a diameter of 50 mm in several sites, open to external users.

In 1972, a collaboration with the Max-Plank-Institut für Festkörperforschung (MPI-FKF) in Stuttgart was launched, and the power was raised to 10 MW. In 1982, this allowed to reach 25 T in a 50 mm bore diameter with polyhelix coils designed by Hans Schneider-Muntau. In such high magnetic fields, Klaus von Klitzing discovered the quantum Hall effect (in Grenoble in the night of 4th to 5th February 1980), for which he got the Physics Nobel Prize in 1985.

A project of hybrid magnet conceived as soon as 1975, is then built from 1980, by a French-german team (under the direction of G. Aubert and G. Landwehr) to reach a new magnetic field record of 31.35T in 50 mm in 1987 . This magnet is composed of a superconducting coil providing 11 T, surrounding a resistive coil providing itself 20,5 T. It was built by J.C. Vallier et Hans Schneider-Muntau.

First hybrid magnet reaching 31.35T in a 50 mm bore diameter, in 1987

At the end of 1989 the partnership MPG – CNRS is marked by the creation of a common laboratory: the GHMFL "Grenoble High Magnetic Field Laboratory" (which will run until the end of 2004). In 1990-91, the electric and hydraulic powers of the facility is doubled to reach 24 MW. In order to remain at the highest international level, the GHMFL started to build a new hybrid coil in 1997. Unfortunately, the superconducting part (of 8 T) was not working and a new superconducting coil is currently under construction (on the basis of new techniques) to reach 43 T in 2015. Great progress in the conception of polyhélix coils (G. Aubert, W. Joss, F. Debray, C. Trophime) permit to improve their performances up to 35T available in a 34 mm diameter in 2008, or 30T in a 50 mm diameter, with the 24 MW power. At the same time, the homogeneity and the stability of the magnetic field have been strongly improved respectively by the geometry of the helix, and by the use of NMR probes (S. Krämer).

In 2009, the Laboratoire National des Champs Magnétiques Intenses (LNCMI) was created, gathering the efforts of the Toulouse laboratory of pulsed magnetic fields and the Grenoble laboratory in static magnetic fields, under the direction of Geert Rikken.