Innovative technique to synthesize C-doped MgB 2 by using chitosan as carbon source G. Bovone, M. Vignolo, C. Bernini, S. Kawale and A. S. Siri Abstract Here we report a new technique to synthesize carbon doped MgB 2 powders. Chitosan was innovatively used as carbon source during synthesis of boron from boron oxide. This allowed to introduce local defects, which later on served as pinning centres in MgB 2 , in boron lattice itself avoiding traditional and time consuming ways of ex-situ MgB 2 doping (e.g. ball milling). Two volume percentage of C-doping have been tried and its effect on superconducting properties, evaluated by magnetic and transport measurements, are discussed here. Morphological analysis by scanning electron microscopy revealed nano-metric grains distribution in boron and MgB 2 powders. Mono-filamentary MgB 2 wires have been fabricated by ex-situ powder in tube technique by using so prepared carbon doped MgB 2 and pure MgB 2 powders. The transport property measurements on these wires were done and compared with MgB 2 wire produced using commercial boron. Index terms - Magnesium diboride, ex-situ, carbon doping, critical current 1. Introduction Since the discovery of superconducting properties of MgB 2 in 2001 [1], it has been one of the main attractions of superconductivity field. Not just because of its highest critical temperature of 39 K amongst conventional superconductors but also due to its structural simplicity and higher critical current densities (J c ) values. Moreover MgB 2 has already proven its worth from application point of view having been successfully used for production of superconducting magnets used for many applications including MRI. Even after this scientific community has been working meticulously to improve its superconducting properties and to realize homogeneous long tapes [2] and wires [3]. Nevertheless huge efforts are still necessary to improve J c and upper critical field (H c2 ) by means of a homogeneous insertion of defects in to the MgB 2 lattice. Carbon has been found to be one of the most suitable dopant for MgB 2 , enhancing J c up to 10 5 A/cm 2 at field of 7 T. Jung et al. [4] suggested that it’s possible to homogeneously arrange C in superconductor’s lattice like small particles which acts as the pinning centres. Also as demonstrated by Zhang et al. in [5], great improvement in H c2 is possible by replacing boron site with carbon. The major problem in introduction and distribution of dopants in MgB 2 crystal lattice occurs due to the different phases of reactant, which involves reaction of solid boron with liquid magnesium. This so large difference in chemical nature of reactant phases is an Achilles’ heel of the MgB 2 synthesis procedure, especially when a homogeneous distribution of dopants is desired. Since the early stages of MgB 2 research, our group has been actively involved in this field and has produced promising results in boron production [6], MgB 2 tape and wire manufacturing [7, 8], ex-situ PIT technique and powder manipulation in order to introduce doping afterwards MgB 2 synthesis [3, 9]. Excellent results in terms of J c enhancement were reached by milling MgB 2 with carbon in tungsten carbide (WC) jar, as well as balls, for 72 and 144 hours under argon atmosphere [9-11]. Unfortunately this process fails scalability tests due to few drawbacks like very long milling time, necessity of Ar atmosphere during whole procedure and bigger WC jars and balls makes it impractical as well as adds into capital expenses. Furthermore we cannot forget the consumption and degradation of the tools themselves. The new process developed in our laboratory permits to obtain doped and un-doped boron, suitable for MgB 2 synthesis [6]. Boron synthesized in this way (defined as laboratory made boron or LB) has amorphous nature with nano-metric grain size and it has shown several advantages respect to commercial boron (CB) powders, which are well explained