Coils with fibre composite reinforcement for pulsed magnetic fields in the 50-70 T range

Abstract

Coils for pulsed magnetic fields were developed using layer by layer reinforcement with fibre composite material. The thickness of each individual layer of the reinforcement was optimized using a simple 'finite element' calculation method. A machine was designed and built that allows the winding of a layer of fibre rovings of precisely controlled thickness between the layers of wire. So far, a field of 58 T has been obtained in a 20 mm bore; in a 12 mm bore a maximum field of 66.9 T resulted in destruction of the coil.

Pulsed magnetic fields as a probe of self-assembled semiconductor nanostructures

“…Photoluminescence (PL) experiments are conducted in 50 T pulsed field coils developed in the laboratory [8] in combination with a 5 kV; 600 kJ capacitor bank [9], though a 70 T user coil connected to a 10 kV; 500 kJ capacitor bank has recently become available [10]. Both 4 He bath and flow cryostats are used for PL experiments making temperatures between 1.5 and 200 K accessible.…”

High-field magnet facilities and associated technology at Oxford

“…The copper layers are separated by a SiC fibre called Zylon tm ; which is added to give sufficient strength to the copper wire. This technique of distributed reinforcement was pioneered in Leuven [3]. A thin layer of carbon fibre was added because of manufacturing reasons: Carbon fibre can be machined after impregnation, leading to an equally shaped former for the following layers.…”

Strength versus conductivity

“…The average stress in the coil is of the order 0.4xB2/2#o [6,7] and depends primarily on the geometry of the magnet and to a moderate degree on the type of winding: compared to coils with uniform winding, a reduction of the average stress can be expected in magnets with radially graded internal reinforcement or multi-section coils. The average stress a imposes a lower boundary condition on the strength of the materials.…”