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Since MgB 2 superconductor was discovered by Akimitsu, many scientists has been studied this new intermediate temperature superconductor material. Recently Dou reported the critical current density and flux pinning of MgB 2 is enhanced by doping of SiC nano powder, and Fujii reported MgB 2 superconductor made by the powder-in-tube in-situ process using MgH 2 as a precursor powder enhanced the critical current density especially under high magnetic field. Also Matsumoto reported the irreversibility field of MgB 2 tape prepared by the in-situ powder in tube process using MgH 2 as a precursor powder increased to 23 T by the SiC doping. These results show MgB 2 has high potential as a strong candidate for a practical use.We study the effects of doping nano carbon impurity because graphite has the same structure as the hexagonal Boron structure in MgB 2 . We added carbon impurities of graphite, C 60 , and open-ended carbon nano tube respectively to MgB 2 conductors made by powder in tube ex-situ process.Index Terms-C 60 , critical current, flux pinning, impurity doping, MgB 2 , powder metallurgy.

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Recently, affinity magnetic beads have been widely used in immunomagnetic cell sorting (IMCS) technology. Today, we can easily sort and analyze DNA and antibodies (immunoglobulin) using various types of affinity magnetic beads available in the market. The diameters of these affinity magnetic beads used in immunomagnetic cell sorting are limited to above approximately 1 m because of the low magnetic fields induced by permanent magnets. Now, nano-sized affinity magnetic beads are strongly desired to achieve high resolutions. We have been studying and attempting to develop a high-gradient magnetic separation (HGMS) system that employs a superconducting magnet to induce a considerably higher magnetic field than that induced by a permanent magnet in order to trap smaller nano-sized affinity magnetic beads by a filter made of fine stainless steel wool. In this study, we constructed a prototype of a desktop-type HGMS system using a cryocooler-cooled LTS magnet and conducted preliminary experiments on trapping the nano-sized magnetic particles. Furthermore, we investigated the magnetic field distribution and magnetic force around a magnetic wire in the filter by means of a numerical simulation.

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