Syju Thomas

Influence of nano-Cu additive on MgB2 phase formation, processing temperature, and transport properties

Pure and nano-Cu doped MgB2/Fe superconducting wires were prepared by in situ powder-in-tube method at different temperatures (550–675 °C). The phase formation, microstructure, and transport critical current density of the wires were investigated as a function of the heat-treatment temperature. A small amount of nano-Cu addition (2.5 wt %) was found to dramatically decrease the reaction temperature of magnesium and boron, forming MgB2 without any degradation in the transport critical current. From x-ray diffraction and scanning electron microscopy analyses, it was found that the added Cu form a reacted phase Mg2Cu with Mg which melts at around 550 °C. This liquid phase helps the formation of MgB2 at a significant lower temperature with improved grain connectivity, grain size, and density. All Cu doped samples heat treated in the range of 550–650 °C exhibited a transport JC quite comparable to that of the pure sample processed at 650 °C, which shows that high quality MgB2 conductors can be produced even at...

On the current transfer length and current sharing in short length MgB2 wires

Current transfer length (CTL) and current sharing with the normal paths for a metal sheathed MgB2 superconductor are studied by analytical and numerical methods. The study was aimed at wire geometries with short sample lengths. The computations show low CTL values for Fe sheathed MgB2 and significantly higher CTL for Cu sheathed MgB2. For short length samples a considerable part of the applied current is not transferred into the superconducting layer and flows through the sheath in Cu sheathed conductors. Close to the current contacts the heat generated due to current sharing with normal paths is significantly higher for the Fe sheath than for the Cu sheath.

An Effort Toward Development of

In this paper, we report an effort toward the development of general-purpose conduction-cooled current leads based on MgB2, which can carry 2000 A at 25 K. The leads have an overall length of 40 cm and a diameter of 5.8 mm, with Cu end caps with a length of 5 cm each for anchoring them to the superconducting system and the current source. Fe, Cu, and Ni are used as the barrier, the stabilizer, and the outer sheath materials, respectively. The critical parameters of the current leads, such as rated current Ic, thermal cycling stability, and heat leak, were tested and evaluated using a cryocooler-integrated cryostat test facility.

\hbox{MgB}_{2}

The effects of addition of nano SiO2 and/or nano diamond on structural and superconducting properties of MgB2 bulk samples were studied. The addition caused systematic reduction in ‘a’ lattice parameter. The in‐field critical current density [JC(H)] of doped samples showed a significant enhancement compared to the undoped sample. The codoped samples exhibited the best results.

-Based Current Leads With 2000-A Rating

A small amount of nano Cu addition (2.5 wt %) was found to dramatically decrease the reaction temperature of magnesium and boron, forming MgB2 without any degradation in the transport critical current. The presence of reacted Mg2Cu liquid phase could accelerate the reaction between Mg and B and finally results in the formation of MgB2 phase even at low temperatures. All Cu doped samples heat treated below 650 °C exhibited highly enhanced transport JC at 30 K and the sample heat treated at 550 °C recorded 30‐fold increase in transport JC compared to the pure sample.

Nano Diamond and Nano SiO2—An Effective Combination to Improve the In‐Field Properties of MgB2 Superconductor

A comparative study on the effect of doping of nano carbon, nano diamond and nano SiC in MgB2 is carried out.The JC(H) is significantly enhanced for all doped samples compared to the pure sample among which MgB1.9C0.1 (nano C) exhibits the best JC(H) performance. The enhanced performance is due to the effective substitution of C at B site which is confirmed by the systematic decrease in both a axis and TC.