The critical current density of advanced internal-Mg-diffusion-processed   MgB2 wires
  Recent advances in MgB2 conductors are leading to a new level of performance. Based on the use of proper powders, proper chemistry, and an architecture which incorporates internal Mg diffusion (IMD), a dense MgB2 structure with not only a high critical current density Jc, but also a high engineering critical current density, Je, can be obtained. In this paper, a series of these advanced (or second - generation, "2G") conductors has been prepared. Scanning electron microscopy and associated energy dispersive X-ray spectroscopy were applied to characterize the microstructures and compositions of the wires, and a dense MgB2 layer structure was observed. The best layer Jc for our sample is 1.07x105 A/cm2 at 10 T, 4.2 K, and our best Je is seen to be 1.67x104 A/cm2 at 10 T, 4.2 K. Optimization of the transport properties of these advanced wires is discussed in terms of B-powder choice, area fraction, and the MgB2 layer growth mechanism. 
G. Z. Li, M. D. Sumption, M. A. Susner, Y. Yang, K. M. Reddy, M. A.   Rindfleisch, M. J. Tomsic, C. J. Thong, and E. W. Collings
cond-mat.supr-con