.8mm 3x3

1. .8mm 3x3 1.5mm 3x3 .8mm 3x4 1.5mm 3x5 .8mm 3x6 Equation 1: Figure 5:Moody Diagrams characterize the geometric properties and surface conditions of the conduit. This diagram allows the flow of different gasses at different temperatures to be estimated. Performance Characterization of Integrated Reinforcement for High-Field Superconductors Nicholas Brown1 with mentor Thomas A. Painter2 1Department of Physics, Colorado School of Mines 2Assistant Director Magnet Science and Technology, National High Magnetic Field Lab ABSTRACT: Development of conductors for very high field superconducting solenoids is challenging due to the strain-sensitivity of the highest field superconductors, namely Nb3Sn and High Temperature Superconducting (HTS) conductors. This project characterizes the potential for miniature Cable in Conduit Conductor (CICC) configurations to be used for a superconducting insert solenoid in background fields of 20T or greater. The primary aspects examined are the hydraulic characteristics (pressure drop versus flow rate), characteristics of the fabrication process, and performance assessment as a high field insert for multiple (CICC) configurations. Equation 2: Figure 4:The pressure drop versus flow rate of the five sample CICCs using N2 gas was measured as input to the more general Moody Diagram which then is used to predict the hydraulic performance for any fluid flow in the conductor for the range tested. Figure 1:The original configuration of miniature CICCs. The conduit was later drawn to create a square cross section. Critical Current of the Winding Pack: The critical current of the winding pack is based on the critical current densities of Nb3Sn at 1.8 K and Bi-2212 at 4.2 K. The higher temperature is used for Bi-2212 because it is slightly resistive, thus it generates heat making it very difficult to cool to 1.8 K. INTRODUCTION: Although Bi2Sr2CaCu2Oy (Bi-2212) shows the most promise as a high temperature and high field superconductor, it has limitations. The reaction process requires the flow of high temperature oxygen. Also Bi-2212 is very strain sensitive but as an insert it experiences very high Lerentz forces. It is anticipated that these miniature CICCs will enable the use of strain sensitive superconductors in very high fields by utilizing the conduit as the primary load support. The initial conduit wall thickness must be varied depending on the calculated final stress and the diameter must be adjusted to change the void fraction. As a first step in the development of miniature CICCs, a range of initial wall thickness and diameters were selected to characterize the fabrication process. Recommendations for future work: The optimum mass flow rate of oxygen for Bi-2212 reaction must be determined. Also, the adequate flow rate of helium for cooling each configuration is needed. A complete stress analysis must be performed to optimize wall thickness. These are the next steps in the design and will allow the tolerances of the miniature CICC configuration to be tightened. CONCLUSION: The mechanical properties of both the conduit and the fluid have been gathered. The measured friction factor versus Reynolds number shows the classical dependence as predicted by the standard Moody diagram. For a given Reynolds number the friction factor increases with increasing hydraulic diameter of the sample. This correlation may be useful for future equation fitting. Figure 3 show that at fields larger than 22.2T Bi-2212 has a higher current density than Nb3Sn. Also the highest current density is achieved in the 0.8 mm 3x6 winding pack. However, this configuration has a much thinner wall than the others, which may present a problem during stress analysis. Figure 2:Micrographs of all five tested CICC configurations. There is wire distortion in 1.5 mm 3x3, wall warping in .8 mm 3x6, and poorly defined corner radius in .8 mm 3x4. Results:The flow and critical current calculations are the first step towards an insert solenoid design. Next the stresses in the conduit must be analyzed and the required O2 flow rate for reacting Bi-2212 determined. • Notable results of forming process: • Wall Warping—The thin-walled conduit buckled during the forming process. This may be due to insufficient number of forming passes or the large void fraction (lack of internal support from the cable) or both. • Corner Radius—the inner corner radius on thick-walled samples was poorly defined. The wall thickness in the corner region was not constant. • Wire Distortion—It appears that the larger, 1.5 mm diameter wires had more wire distortion. Acknowledgements: A special thanks all these in the Magnetic Science and Technology division who helped make this project possible. Thanks to the NHMFL and the National Science Foundation. Also a thanks all those who helped with the fabrication work; without their help this would not have been possible. REFERENCES: [1] T.A. Painter, “Conceptual Design of a Superconducting 30T Solenoid Using Wire-in-Conduit Conductors,” IEEE Trans. in Appl. Supercond., vol.15, no.2, pp. 1427-1430, 2005 [2] K.R. Marken Jr., H. Miao, M. Meinesz, B. Czabaj, and S. Hong, “Progress in Bi-2212 Wires for High Magnetic Field Applications,” IEEE Trans. in Appl. Supercond., vol.16, no.2, pp. 992-995, 2006 [3] T.G. Holesinger, J.M. Johnson, J.Y. Coulter, H. Safar, D.S. Phillips, J.F. Bingert, B.L. Bingham, M.P. Maley, J.L. Smith, D.E. Peterson, “Isothermal melt process of Bi2Sr2CaCu2Oy round wire,” Physica C 253, pp. 182-190, 1995 Fluid Flow Properties: Each sample has a different void fraction so Figure 4 shows the mass flow rate versus pressure drop for five different void fractions. The following figure shows a Moody Diagram, Darcy friction factor versus Reynolds number, for each conduit: see Equation 1 and 2. From this the flow for 800°C oxygen used in the isothermal melt process Bi-2212 conductors can be determined. Also the flow of 4.2 K helium can be estimated. Figure 3:Critical current density of a winding pack in a given background field. Jc at 1.8 K is used for the Nb3Sn samples and for Bi-2212 Jc at 4.2 K is used. It is assumed that the wire diameter has no effect on Jc. Table 1: A brief summery of conduit properties.