The 20 MW-50 mm bore diameter magnet of the Grenoble High Magnetic Field Laboratory

A 30 Tesla-20 MW magnet with a 50 mm bore was set into operation at the Grenoble High Magnetic Field Laboratory (GHMFL) in April 1998. It is made of two 10 MW magnets. The inner magnet is composed of a series of 10 helices, electrically in parallel with two thin Bitter coils connected in series. We give the specifications of this magnet and present the design of the 14 helix insert which is now under construction for a 34 mm bore magnet.