@article{ye_li_jaroszynski_schwartz_shen_2017, title={Strain control of composite superconductors to prevent degradation of superconducting magnets due to a quench: I. Ag/Bi2Sr2CaCu2Ox multifilament round wires}, volume={30}, ISSN={["1361-6668"]}, DOI={10.1088/0953-2048/30/2/025005}, abstractNote={The critical current of many practical superconductors is sensitive to strain, and this sensitivity is exacerbated during a quench that induces a peak local strain which can be fatal to superconducting magnets. Here, a new method is introduced to quantify the influence of the conductor stress and strain state during normal operation on the margin to degradation during a quench, as measured by the maximum allowable hot spot temperature Tallowable, for composite wires within superconducting magnets. The first conductor examined is Ag-sheathed Bi2Sr2CaCu2Ox round wire carrying high engineering critical current density, JE, of 550 A mm−2 at 4.2 K and 15 T. The critical axial tensile stress of this conductor is determined to be 150 MPa and, in the absence of Lorentz forces, Tallowable is greater than 450 K. With increasing axial tensile stress, σa, however, Tallowable decreases nonlinearly, dropping to 280 K for σa = 120 MPa and to 160 K for σa = 145 MPa. Tallowable(σa) is shown to be nonlinear and independent of magnetic field from 15 to 30 T. Tallowable(σa) dictates the balance between magnetic field generation, which increases with the magnet operating current and stress, and the safety margin, which decreases with decreasing Tallowable, and therefore has important engineering value. It is also shown that Tallowable(σa) can be predicted accurately by a general strain model, showing that strain control is the key to preventing degradation of superconductors during a quench.}, number={2}, journal={SUPERCONDUCTOR SCIENCE & TECHNOLOGY}, author={Ye, Liyang and Li, Pei and Jaroszynski, Jan and Schwartz, Justin and Shen, Tengming}, year={2017}, month={Feb} }
 @article{ye_li_shen_schwartz_2016, title={Quench degradation limit of multifilamentary Ag/Bi2Sr2CaCu2Ox round wires}, volume={29}, ISSN={["1361-6668"]}, DOI={10.1088/0953-2048/29/3/035010}, abstractNote={Understanding safe operating limits of composite superconducting wires is important for the design of superconducting magnets. Here we report measurements of quench-induced critical current density Jc degradation in commercial Ag/Bi2Sr2CaCu2Ox (Bi-2212) round wires using heater-induced quenches at 4.2 K in self magnetic field that reveal a general degradation behavior. Jc degradation strongly depends on the local hot spot temperature Tmax, and is nearly independent of operating current, the temperature gradient along the conductor dTmax/dx, and the temperature rising rate dTmax/dt. Both Jc and n value (where n is an index of the sharpness of the superconductor-to-normal transition) exhibit small but irreversible degradation when Tmax exceeds 400–450 K, and large degradation occurs when Tmax exceeds 550 K. This behavior was consistently found for a series of Bi-2212 wires with widely variable wire architectures and porosity levels in the Bi-2212 filaments, including a wire processed using a standard partial melt process and in which Bi-2212 filaments are porous, an overpressure processed wire in which Bi-2212 filaments are nearly porosity-free and that has a Jc(4.2 K, self field) exceeding 8000 A mm−2, and a wire that has nearly no filament to filament bridges after reaction. Microstructural observations of degraded wires reveal cracks in the Bi-2212 filaments perpendicular to the wire axis, indicating that the quench-induced Ic degradation is primarily driven by strain. These results further suggest that the quench degradation temperature limit depends on the strain state of Bi-2212 filaments and this dependence shall be carefully considered when engineering a high-field Bi-2212 magnet.}, number={3}, journal={SUPERCONDUCTOR SCIENCE & TECHNOLOGY}, author={Ye, Liyang and Li, Pei and Shen, Tengming and Schwartz, Justin}, year={2016}, month={Mar} }
 @article{shen_ye_turrioni_li_2015, title={High-field quench behavior and dependence of hot spot temperature on quench detection voltage threshold in a Bi2Sr2CaCu2Ox coil}, volume={28}, number={7}, journal={Superconductor Science & Technology}, author={Shen, T. M. and Ye, L. Y. and Turrioni, D. and Li, P.}, year={2015} }
 @article{ye_cruciani_xu_mine_amm_schwartz_2015, title={Magnetic field dependent stability and quench behavior and degradation limits in conduction-cooled MgB2 wires and coils}, volume={28}, ISSN={["1361-6668"]}, DOI={10.1088/0953-2048/28/3/035015}, abstractNote={Long lengths of metal/MgB2 composite conductors with high critical current density (Jc), fabricated by the powder-in-tube process, have recently become commercially available. Owing to its electromagnetic performance in the 20−30 K range and relatively low cost, MgB2 may be attractive for a variety of applications. One of the key issues for magnet design is stability and quench protection, so the behavior of MgB2 wires and magnets must be understood before large systems can emerge. In this work, the stability and quench behavior of several conduction-cooled MgB2 wires are studied. Measurements of the minimum quench energy and normal zone propagation velocity are performed on short samples in a background magnetic field up to 3 T and on coils in self-field and the results are explained in terms of variations in the conductor architecture, electrical transport behavior, operating conditions (transport current and background magnetic field) and experimental setup (short sample versus small coil). Furthermore, one coil is quenched repeatedly with increasing hotspot temperature until Jc is decreased. It is found that degradation during quenching correlates directly with temperature and not with peak voltage; a safe operating temperature limit of 260 K at the surface is identified.}, number={3}, journal={SUPERCONDUCTOR SCIENCE & TECHNOLOGY}, author={Ye, Liyang and Cruciani, Davide and Xu, Minfeng and Mine, Susumu and Amm, Kathleen and Schwartz, Justin}, year={2015}, month={Mar} }
 @inproceedings{li_ye_jiang_shen_2015, title={RRR and thermal conductivity of Ag and Ag-0.2 wt.% Mg alloy in Ag/Bi-2212 wires}, volume={102}, booktitle={Advances in cryogenic engineering - materials: proceedings of the international cryogenic materials conference (icmc) 2015}, author={Li, P. and Ye, L. and Jiang, J. and Shen, T.}, year={2015} }
 @article{ishmael_luo_white_hunte_liu_mandzy_muth_naderi_ye_hunt_et al._2013, title={Enhanced Quench Propagation in Bi2Sr2CaCu2Ox and YBa2Cu3O7-x Coils via a Nanoscale Doped-Titania-Based Thermally Conducting Electrical Insulator}, volume={23}, ISSN={["1558-2515"]}, DOI={10.1109/tasc.2013.2269535}, abstractNote={The significant amount of energy stored in a large high-field superconducting magnet can be sufficient to destroy the coil in the event of an unprotected quench. For magnets based on high-temperature superconductors (HTSs), such as Bi2Sr2CaCu2Ox (Bi2212) and YBa2Cu3O7-x (YBCO), quench protection is particularly challenging due to slow normal zone propagation. A previous computational study showed that the quench behavior of HTS magnets is significantly improved if the turn-to-turn electrical insulation is thermally conducting, enhancing 3-D normal zone propagation. Here, a new doped-titania electrical insulation with high thermal conductivity is evaluated. The thermal conductivity of the insulation is measured at cryogenic temperatures, and its chemical compatibility with Bi2212 round wires is determined. Thin layers of the insulation are deposited onto the surface of Bi2212 and YBCO wires, which are then wound into small coils to study the quench behavior. Results show that the critical current and homogeneity of Bi2212 coils are improved relative to coils reacted with mullite insulation. Relative to similar coils with conventional insulation (mullite for Bi2212 and Kapton for YBCO), the turn-to-turn quench propagation is increased by a factor of 2.8 in Bi2212 coils at 4.2 K and self-field and by a factor of 2.5 in YBCO coils at 4.2 K and 5 T. These results indicate that doped-titania insulation may significantly improve Bi2212 and YBCO coils. Increased normal zone propagation velocity enhances quench detection and quench protection, and the thinness of the insulation relative to the most common alternatives increases the magnet winding pack current density and reduces the coil specific heat.}, number={5}, journal={IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY}, author={Ishmael, Sasha and Luo, Haojun and White, Marvis and Hunte, Frank and Liu, X. T. and Mandzy, Natalia and Muth, John F. and Naderi, Golsa and Ye, Liyang and Hunt, Andrew T. and et al.}, year={2013}, month={Oct} }
 @article{ye_cruciani_effio_hunte_schwartz_2013, title={On the Causes of Degradation in Bi2Sr2CaCu2O8+x Round Wires and Coils by Quenching at 4.2 K}, volume={23}, ISSN={["1558-2515"]}, DOI={10.1109/tasc.2013.2271255}, abstractNote={One of the remaining challenges for the implementation of commercial Ag-alloy-sheathed $\hbox{Bi}_{2}\hbox{Sr}_{2}\hbox{CaCu}_{2}\hbox{O}_{8+{\rm x}}$ (Bi2212) wires in high-field superconducting magnets is quench protection. To develop an effective quench protection system, it is important to understand the conditions that must be avoided during a quench so that the conductor is not degraded. While these conditions are understood for NbTi and $\hbox{Nb}_{3} \hbox{Sn}$, they are conductor specific and there remains a lack of data and understanding of the limiting conditions for Bi2212 wires. Here, quenches are induced in short strands and small coils of Bi2212 round wires at 4.2 K. The quench conditions are varied to identify the threshold conditions resulting in wire degradation. These conditions are quantified in terms of the maximum temperature, the maximum time rate of change of the temperature, and the maximum temperature spatial gradient along the length of the wire. It is found that the time rate of change of the temperature (thermal shock) is not a primary driver for degradation but that both the maximum temperature and its spatial gradient play a key role. It is not clear, however, whether the temperature gradient along the length of the wire, or radially from the center of the wire to the surface, dominates. It is also found that threshold values for these parameters vary between different Bi2212 wires and, thus, must be identified for the specific wire to be used in a magnet system. Implications of these results on quench protection are discussed.}, number={5}, journal={IEEE TRANSACTIONS ON APPLIED SUPERCONDUCTIVITY}, author={Ye, Liyang and Cruciani, Davide and Effio, Timothy and Hunte, Frank and Schwartz, Justin}, year={2013}, month={Oct} }