G. Heremans

Cu-Ag wire pulsed magnets with and without internal reinforcements

Multilayer wire wound coils for pulsed magnets with long pulse duration were manufactured using a newly developed Cu-Ag microcomposite wire which has excellent properties of high conductivity, high mechanical strength and high homogeneity along the wire. Test results of magnets with various bore diameters both with and without internal reinforcements proved the usefulness of this new wire. One of the magnets wound with inter layer reinforcements generated a magnetic field of 68.0 T with a 1.9 ms rise time and a 3 ms decay time in the space of a 12.2 mm inner winding diameter. >

The K.U. Leuven pulsed high magnetic field facility

Abstract The pulsed field installation at the K.U. Leuven is upgraded for the development and use of the new generation of high performance coils with peak fields in the 60–70 T range. New equipment includes an improved coil winding installation, capacitor bank switchgear and electrical diagnostics to enable the running of two experiments in parallel, new cryostats for stabilized temperatures in the 300–0.4 K range, sample holders whixh permit rotation of the sample, and facilities for sample preparation.

Coppersilver wire coils for pulsed magnet

Abstract A newly developed Cu-16 at % Ag alloy wire was evaluated by using it to wind multilayered coils for pulsed magnets with different bore diameters, with and without internal reinforcement by glass fiber composites. These magnets have a long pulse duration in the range 5–10ms. A peak field of 62.7 T was obtained in 15 mm bore of a coil without internal reinforcement but enclosed in an outer metal case. A magnet with optimized layer by layer reinforcement succeeded in generating 73.4 T in the 10 mm bore. It was thus established that this wire is highly promising for the construction of high performance pulsed magnets.

High performance coils for pulsed magnets

In the framework of the EUROMAGTECH cooperation, several coils for pulsed magnetic fields were developed and tested for their ultimate performance. A winding machine was developed which can reinforce each layer of conductor with a uniaxial wrap of fibers. Thus, optimum reinforcement can be obtained which resulted in coils producing 67 T in a 12-mm bore and 58 T in a 20-mm bore. Alternatively, a cable of pearlitic steel around a copper core was developed at BEKAERT, resulting in a wire with a strength of more than 1 GPa at a room-temperature conductivity of 60% IACS. This wire was wound into a coil with a bore of 17 mm, producing 54-T without noticeable radial deformation of the coil. >

The pulsed field installation at the K.U. Leuven

Abstract The pulsed field laboratory at the University of Leuven is described. The power is obtained from two 500-kJ capacitor banks, one at 5/10 kV (convertible) and one at 10 kV. Instrumentation is avvailable for sensitive electrical measurements and experiments with far infrared radiation.

Strong pulsed magnetic fields combined with very low temperatures

Abstract New types of pulsed field coils have been developed: optimized reinforcement by fibre composites has yielded ultimate peak fields of 67T in a 12 mm bore and 58T in a 20 mm bore, and a coil made with a newly developed cable of pearlitic steel wires around a copper core has reached 55T in a 17 mm bore. The temperature range of pulsed field experiments has been extended into the 400 mK range by means of top-loading 3He cryostats. Experiments with the fractional quantum Hall effect have shown that sample heating due to eddy currents can be kept within acceptable limits but it becomes critical for a pulse duration of 10 ms or less.

Switching of a 0.5-MJ capacitor bank with thyristors at surge ratings

Abstract The design of a thyristor switch for a 500-kj, 5-kV capcitor bank is described. Four optically triggered high power thyristors are connected in series-parallel, with protection against overload. They are used repeatedly ar surge ratings in single shot operation.

The development of high performance pulsed magnets at the Katholieke Universiteit Leuven

Coils for pulsed magnets in the 50-100 T range are developed with optimized combinations of conductor and reinforcement. The basic design tool is a series of PC codes calculating the capacitor discharge, conductor heating, mechanical stress and residual stresses from plastic deformation and winding tension. Equipment includes a coil winding machine which permits the controlled insertion of layers of fibre rovings between windings and around wires, an installation for flow-through vacuum impregnation at controlled temperatures, and a 1 MJ capacitor bank with diode crowbar. The diagnostics for coil testing includes multi-channel digital recorders and instrumentation for calibration of the field measurement by means of far infrared resonances, slid for the precise measurement of resistance and inductance which is used to monitor the irreversible deformation of the coil in a series of test pulses. >

Fibre composites combined with matched high strength Cu-Nb microfilament conductors for high performance pulsed magnets

High performance pulsed magnets for fields in excess of 70 T at a pulse duration of 15 ms are made by combining strong fibre composites with different types of conductor materials. These solenoids are optimized for constant stress throughout the volume. The best results are obtained when the modulus of elasticity of the conductor is matched to that of the fibre composite. To this end, a high strength Cu-Nb microfilament wire has been developed that matches the modulus of all S-glass fibre composite. >

Investigations of electrophysical and mechanical properties of high-strength Cu-Nb composites for pulse magnetic system winding wires

Melting by consumable electrode vacuum arc melting and casting processes for ingots of pseudo-alloy Cu-Nb with Nb content of up to 20% have been investigated. The effect of the degree of deformation of composites with different Nb content in the initial alloy on strength properties has been investigated. The process for manufacturing long-length composite conductors of rectangular cross-section 3 mm/spl times/2 mm of various designs has been developed. The application of the method of repeat assembling has been shown to allow the variation over a sufficiently wide range of the electrical and mechanical parameters of conductors with large cross section area. Thus, for wires with 6 mm in cross section, relative elongation values of 3-8%, ultimate tensile strength values of 0.7-1.1 GPa (at room temperature) and electroconductivity of 50-80% of IACS are achievable. The results of wire testing in high-field pulsed magnet windings are given. >