DC High Field Magnets at the LNCMI

The Laboratoire National des Champs Magnetiques Intenses (LNCMI) is a French large scale facility enabling researchers to perform experiments in the highest possible magnetic field. DC magnetic fields up to 35 T are provided at the Grenoble site and pulsed fields up to 80 T at Toulouse. We focus in this paper on the latest developments of the polyhelix technologies which is used for the most constrained parts of the dc high field magnets. In November 2010, LNCMI has achieved the standardization of its three 24 MW magnets sites (which includes the site for the new 42 T+ hybrid magnet); longitudinally cooled polyhelix inserts are now systematically used as the innermost part of these magnets. The on-going developments aim at developing "hybrid" polyhelix inserts incorporating radially cooled helices in the center to decrease the thermal constraints and to reach higher magnetic fields with the maximal power presently available on the Grenoble site (24 MW). We give an overview of these developments which combine both numerical and experimental approaches.