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The stability of the [Nb.sub.3]Sn superconducting wires is analyzed and shown as a critical issue in the design and operation of reliable superconducting magnets. The evidence of a different qualitative behavior of the voltage traces recorded on [Nb.sub.3]Sn strands with respect to NbTi strands is described by using a model of [Nb.sub.3]Sn strands, which has considered electrical and thermal transverse resistances.

A superconducting magnet with 200 kJ stored energy and 75 kW output/input power is designed, manufactured and preliminary tests are conducted. Several tests with different ramp rate are carried out at the liquid helium temperature and the design and manufacturing characteristics are characteristics.

Liquid storage of gaseous fuel on board of vehicles as possible alternative to high-pressure storage is receiving an increasing attention because of the higher mileage, the lower cost of the tank, and the faster refill allowable. The research effort devoted to liquid storage is also boosting the advance of cryogenics on board of vehicles, thus opening the way to the synergic use of superconductors. In such a context, superconducting magnetic energy storage (SMES) for regenerative braking may represent a possible alternative to electrochemical batteries or to developing technologies such as supercapacitors or flywheels. In this paper, the feasibility of SMES for regenerative braking on board of hybrid vehicles with cryogenic fuel tank is investigated. Possible application scenarios are discussed. The design of the superconducting magnet based on commercially available superconducting tapes and the cooling are addressed. The performance of the power control system is also investigated by means of a MATLAB/Simulink simulation model. [ABSTRACT FROM AUTHOR]

The thermal and electrical conductivities of the normal matrix of LTS wires have a remarkable influence on the wire stability. In particular, in Nb3Sn wires, a bronze matrix in the region of the superconducting filaments may act as a thermal and electrical barrier between the filaments and the copper matrix. This phenomenon is analyzed here through a numerical model accounting for these thermal and electrical transverse resistances. The model is applied to a parametric analysis of the effect of the main properties of the wire matrix on the quench energy and velocity. A 2D analysis of the wire cross section is applied to investigate how a configuration change could improve the wire stability. [ABSTRACT FROM AUTHOR]

A novel energy storage system based on a SMES cooled by cryogenic fuel is being developed at the Dept. of Electrical Engineering of the University of Bologna. The system represents an alternative solution with respect to nowadays battery packs for the storage of electrical energy with large specific power. The device may find suitable application on board of road vehicles fed by liquid hydrogen with hybrid power-train (internal combustion engine and electric motor/generation), where a cryogenic tank is already present and no additional cryogenic costs are needed. The housing of the SMES inside the tank used for fuel storage, allows the exploitation of the thermal power required for the continuous evaporation of fuel for feeding the engine to remove the AC losses from the magnet, thus avoiding the need of externally supplied cooling power. In this paper both the design of the magnet and its operation in combination with electronic converter and electric motor/generator during charge/discharge cycles are discussed. Moreover the ongoing activity for the development of a laboratory-scale prototype using MgB2 superconductor is presented. [ABSTRACT FROM AUTHOR]

The stability of Nb3Sn superconducting wires is a crucial issue in the design and operation of reliable superconducting magnets. High current density magnets, such as those presently developed for future accelerator projects, may be subject to premature quenches due to local releases of energy. In this paper we study the results of stability experiments that have been performed using a single mode Diode Laser with an optical fiber to illuminate the superconducting strand surface and trigger fast quenches. The development and propagation of laser-induced quenches have been measured on Nb3Sn strands in LHe bath by means of three voltage taps. This paper deals with the numerical analysis of the experimental results. A coupled electric and thermal model has been developed to study the quench propagation. The experimental evidence of a different qualitative behavior of the voltage traces recorded on Nb3Sn strands with respect to NbTi strands is explained by means of a more detailed physical model of Nb3Sn strands, that takes into account electrical and thermal transverse resistances. [ABSTRACT FROM AUTHOR]

A superconducting magnet with 200 Id stored energy and 75 kW output/input power has been designed and manufactured. The device, which is aimed to power quality enhancement in electric grid, consists of two coaxial coils, counter-series connected in order to keep the stray field below the limit of 0.5 mT. The SC wire is a copper stabilized Nb-Ti strand. Several copper slabs are placed within the coils in order to permit heat removal deep inside the coil, thus allowing cryogen-free cooling and operation at high AC losses regime. Several tests with different ramp rate have been carried out at the liquid helium temperature. Design and manufacturing characteristics as well as test results are discussed in this paper. [ABSTRACT FROM AUTHOR]