The element diffusion process of Nb_3Sn superconductors by bronze route was studied using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The critical current of superconductors was...The element diffusion process of Nb_3Sn superconductors by bronze route was studied using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The critical current of superconductors was measured by four-point method. The results show that a diffusion layer has formed around the boundaries between the filaments and bronze matrix after 15 h heat treatment. The diffusion layer thickness keeps stable after heat treatment duration of 50~75 h. The stable and solid Nb 3 Sn layer is obtained in the sample after 100 h heat treatment. Excessive heat treatment would induce superconductivity degeneration because of superconductor grain coarsening. The characteristics of the element diffusion process were discussed. The diffusion of tin atom is the governing factor in diffusion. In this study, Nb_3_Sn superconductors with good superconducting property were fabricated successfully at 670 °C after 100h heat treatment.展开更多
The diffusion process of Sn in the transformation of Nb_6Sn_5 to Nb_3Sn has been studied.The experimental results show that the growth of Nb_3Sn laver is controlled by two processes,i.e. the short range diffusion of S...The diffusion process of Sn in the transformation of Nb_6Sn_5 to Nb_3Sn has been studied.The experimental results show that the growth of Nb_3Sn laver is controlled by two processes,i.e. the short range diffusion of Sn which is responsihle for the inner layer with large grains,and the long,range diffusion of Sn which results in the outer layer with fine grains.It was found thai grain size depends on the reaction temperature.A model of Nb_3Sn growth based on the above processes was established and its solution was found to be in good agreement with ex- perimental results.展开更多
Boundary conditions constructed by two typical geometrical configurations related to the manufacturing methods of bronze process and tin-rich Nb tube method have been considered in a diffusion model in which the diffu...Boundary conditions constructed by two typical geometrical configurations related to the manufacturing methods of bronze process and tin-rich Nb tube method have been considered in a diffusion model in which the diffusion of Sn in CuSn matrix plays a major role is as- sumed.The dependence of thickness of Nb_3Sn layer on reaction time has been derived.It is shown that the growth rate of Nb_3Sn relates to the configuration of the superconductor,the geometrical parameters of Nb filaments and CuSn matrix.The theory is qualitatively con- sistent with the experimental results.展开更多
Low-temperature synthesis of Nb_(3)Sn thin-film cavity is of great significance in the field of superconducting radio frequency(SRF).The bronze process can grow only stable Nb_(3)Sn phase at 700℃,so it is considered ...Low-temperature synthesis of Nb_(3)Sn thin-film cavity is of great significance in the field of superconducting radio frequency(SRF).The bronze process can grow only stable Nb_(3)Sn phase at 700℃,so it is considered to be the most promising process for low-temperature synthesis of Nb3Sn thin-film cavity.We successfully fabricated the worldwide first Nb_(3)Sn thin-film cavity by bronze process.We technically solved the key problems of precursor preparation,characterized and analyzed the uniformity of the Nb_(3)Sn film,and tested the performance of the cutout samples and the whole cavity of the Nb_(3)Sn film.It is obtained that the Q0value of the cavity at 4.2 K is about 1.2×10^(9),which is greater than the performance of the bulk-niobium cavity under the same conditions.This result means that the preparation of Nb_(3)Sn by bronze process has the great potential to more practical copper-based Nb_(3)Sn thin-film cavity,which is expected to achieve a substantial improvement in the performance of SRF cavity and comprehensive engineering applications.展开更多
High-field superconducting magnets are poised to revolutionize technologies,including particle accelerators,magnetic resonance imaging(MRI)machines,and fusion reactors.They stand at the frontier of superconductor inno...High-field superconducting magnets are poised to revolutionize technologies,including particle accelerators,magnetic resonance imaging(MRI)machines,and fusion reactors.They stand at the frontier of superconductor innovation.Nb_(3)Sn wires,which operate at cold temperatures,along with rare-earth barium copper oxide(REBCO)coated conductors that include rare earth elements like Y,Gd,and Dy,are gaining preference.Their high electrical efficiency in strong magnetic fields makes them particularly attractive for such advanced applications.展开更多
In order to verify the feasibility of applying high-Jc Nb_(3)Sn strand in fusion magnet,a full-size cable-in-conduit conductor(CICC)with short twist pitch(STP)cable pattern was manufactured and tested in SULTAN facili...In order to verify the feasibility of applying high-Jc Nb_(3)Sn strand in fusion magnet,a full-size cable-in-conduit conductor(CICC)with short twist pitch(STP)cable pattern was manufactured and tested in SULTAN facility at SPC,Switzerland.Three levels of cyclic electromagnetic(EM)load were applied on the sample stepwise,no visible decrease of current sharing temperature(TcsT was observed until the EM load increased to 80 kA×10.8 T,after that the Tcs decreased dramatically with the EM cycles,which suggested that irreversible deformation,causing a change in the strain state,or even damage has occurred in the superconducting strands.For investigating the reason which caused the conductor performance degradation,the tested conductor was dissected for metallographic observation.Eight segments which subjected to different EM loads were extracted from one of the legs,the geometric feature changes of the cable cross-sections were analyzed and compared.A good correlation was found between the decrease of the Tcs and deformation of the cable cross section.A mass of cracks were found on the sub-elements of strands in the segment which subjected to highest EM load,but the amount of crack is much lower in other segments.Combining the analyses,it is speculated that the critical EM load which causes irreversible degradation is between 850 kN/m and 870 kN/m for this conductor.The results could be a reference in high-Jc Nb_(3)Sn CICC design.展开更多
基金supported by the National Natural Science Foundation of China(No.50925726)
文摘The element diffusion process of Nb_3Sn superconductors by bronze route was studied using X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The critical current of superconductors was measured by four-point method. The results show that a diffusion layer has formed around the boundaries between the filaments and bronze matrix after 15 h heat treatment. The diffusion layer thickness keeps stable after heat treatment duration of 50~75 h. The stable and solid Nb 3 Sn layer is obtained in the sample after 100 h heat treatment. Excessive heat treatment would induce superconductivity degeneration because of superconductor grain coarsening. The characteristics of the element diffusion process were discussed. The diffusion of tin atom is the governing factor in diffusion. In this study, Nb_3_Sn superconductors with good superconducting property were fabricated successfully at 670 °C after 100h heat treatment.
文摘The diffusion process of Sn in the transformation of Nb_6Sn_5 to Nb_3Sn has been studied.The experimental results show that the growth of Nb_3Sn laver is controlled by two processes,i.e. the short range diffusion of Sn which is responsihle for the inner layer with large grains,and the long,range diffusion of Sn which results in the outer layer with fine grains.It was found thai grain size depends on the reaction temperature.A model of Nb_3Sn growth based on the above processes was established and its solution was found to be in good agreement with ex- perimental results.
文摘Boundary conditions constructed by two typical geometrical configurations related to the manufacturing methods of bronze process and tin-rich Nb tube method have been considered in a diffusion model in which the diffusion of Sn in CuSn matrix plays a major role is as- sumed.The dependence of thickness of Nb_3Sn layer on reaction time has been derived.It is shown that the growth rate of Nb_3Sn relates to the configuration of the superconductor,the geometrical parameters of Nb filaments and CuSn matrix.The theory is qualitatively con- sistent with the experimental results.
基金supported by the National Natural Science Foundation of China(Grant Nos.12075295 and 12105335)。
文摘Low-temperature synthesis of Nb_(3)Sn thin-film cavity is of great significance in the field of superconducting radio frequency(SRF).The bronze process can grow only stable Nb_(3)Sn phase at 700℃,so it is considered to be the most promising process for low-temperature synthesis of Nb3Sn thin-film cavity.We successfully fabricated the worldwide first Nb_(3)Sn thin-film cavity by bronze process.We technically solved the key problems of precursor preparation,characterized and analyzed the uniformity of the Nb_(3)Sn film,and tested the performance of the cutout samples and the whole cavity of the Nb_(3)Sn film.It is obtained that the Q0value of the cavity at 4.2 K is about 1.2×10^(9),which is greater than the performance of the bulk-niobium cavity under the same conditions.This result means that the preparation of Nb_(3)Sn by bronze process has the great potential to more practical copper-based Nb_(3)Sn thin-film cavity,which is expected to achieve a substantial improvement in the performance of SRF cavity and comprehensive engineering applications.
文摘High-field superconducting magnets are poised to revolutionize technologies,including particle accelerators,magnetic resonance imaging(MRI)machines,and fusion reactors.They stand at the frontier of superconductor innovation.Nb_(3)Sn wires,which operate at cold temperatures,along with rare-earth barium copper oxide(REBCO)coated conductors that include rare earth elements like Y,Gd,and Dy,are gaining preference.Their high electrical efficiency in strong magnetic fields makes them particularly attractive for such advanced applications.
基金the National Natural Science Foundation of China(Grant Nos.11602185,11972271,and 12322208)the Young Elite Scientists Sponsorship Program by CAST(Grant No.2020QNRC001)the Fundamental Research Funds for the Central Universities.
基金supported by the National Key R&D Program of China(Grant No.2017YFE0301404)the Comprehensive Research Facility for Fusion Technology Program of China under Contract No.2018-000052-73-01-001228。
文摘In order to verify the feasibility of applying high-Jc Nb_(3)Sn strand in fusion magnet,a full-size cable-in-conduit conductor(CICC)with short twist pitch(STP)cable pattern was manufactured and tested in SULTAN facility at SPC,Switzerland.Three levels of cyclic electromagnetic(EM)load were applied on the sample stepwise,no visible decrease of current sharing temperature(TcsT was observed until the EM load increased to 80 kA×10.8 T,after that the Tcs decreased dramatically with the EM cycles,which suggested that irreversible deformation,causing a change in the strain state,or even damage has occurred in the superconducting strands.For investigating the reason which caused the conductor performance degradation,the tested conductor was dissected for metallographic observation.Eight segments which subjected to different EM loads were extracted from one of the legs,the geometric feature changes of the cable cross-sections were analyzed and compared.A good correlation was found between the decrease of the Tcs and deformation of the cable cross section.A mass of cracks were found on the sub-elements of strands in the segment which subjected to highest EM load,but the amount of crack is much lower in other segments.Combining the analyses,it is speculated that the critical EM load which causes irreversible degradation is between 850 kN/m and 870 kN/m for this conductor.The results could be a reference in high-Jc Nb_(3)Sn CICC design.
