High Temperature Superconductor(HTS)materials can operate at higher magnetic fields up to 20 T with high critical current and higher operating temperature,compared to low temperature superconductors(LTS).A Highly Flex...High Temperature Superconductor(HTS)materials can operate at higher magnetic fields up to 20 T with high critical current and higher operating temperature,compared to low temperature superconductors(LTS).A Highly Flexible REBCO Cable(HFRC)is introduced at the Institute of Plasma Physics,Chinese Academy of Sciences(ASIPP);a cabling method that is suitable for REBCO HTS tape having anisotropic material properties in its thin REBCO layer.This type of HTS superconducting cable shows high potential for applications in nuclear fusion.The alternating currents and magnetic fields in tokamak type of fusion magnets,cause AC power losses in such cables,which can provoke instability of the conductor by induced currents and increase the temperature.As a first step in characterizing the electromagnetic(EM)performance of an HFRC cable,the AC loss and contact resistance of the HFRC prototype cable were measured at the University of Twente.The measurements were done in liquid helium(4.2 K)with AC magnetic fields,applied perpendicular to the cable's long axis.The AC loss was measured simultaneously by a calibrated gas flow calorimeter utilizing the helium boil-off method,and by the magnetization method using pick-up coils.For the applied test conditions,no coupling loss could be distinguished as a part of the overall AC loss.It is suggested that this might be explained by the shielding of the conductor interior from the applied magnetic field by the outer tape layer due to the high critical current density of the REBCO tape,leading to a high penetration field.展开更多
Pure phase Y_(3)Fe_(5)O_(12)(YIG)ceramic was successfully produced by tape-casting forming process and one-step solid-state sintering method.The activation energy for densification was calculated to be 183.81 kJ/mol.P...Pure phase Y_(3)Fe_(5)O_(12)(YIG)ceramic was successfully produced by tape-casting forming process and one-step solid-state sintering method.The activation energy for densification was calculated to be 183.81 kJ/mol.Pure YIG ceramic with a relative density as high as 99.8%was fabricated.The existence of O vacancy and Fe^(2+)ions was determined by XPS and EPR spectra.The RT saturation magnetization was measured to be 28.2 emu/g,and the hysteresis loss was calculated to be smaller than 10 mJ/kg in the temperature range of 230~360 K and be as high as 238.8 mJ/kg at 30 K.The dielectric loss tangent tanδ_(ε)was nearly zero at 6~7 GHz and 11~12 GHz.For complex permeability in the frequency range of 5~18 GHz,the magnetic loss tangent tanδ_(μ)fluctuated at around zero.Therefore,the low values of tanδ_(ε)and tanδ_(μ)indicate that it is a low loss ceramic material.展开更多
基金supported by the Strategic Priority Research Program of Chinese Academy of Science under Grant No.XDB25000000Comprehensive Research Facility for Fusion Technology Program of China under Contract No.2018-000052-73-01-001228+2 种基金the National Nature Science Foundation of China(No.52077212)the Youth Innovation Promotion Association,Chinese Academy of ScienceChina Scholarship Council.
文摘High Temperature Superconductor(HTS)materials can operate at higher magnetic fields up to 20 T with high critical current and higher operating temperature,compared to low temperature superconductors(LTS).A Highly Flexible REBCO Cable(HFRC)is introduced at the Institute of Plasma Physics,Chinese Academy of Sciences(ASIPP);a cabling method that is suitable for REBCO HTS tape having anisotropic material properties in its thin REBCO layer.This type of HTS superconducting cable shows high potential for applications in nuclear fusion.The alternating currents and magnetic fields in tokamak type of fusion magnets,cause AC power losses in such cables,which can provoke instability of the conductor by induced currents and increase the temperature.As a first step in characterizing the electromagnetic(EM)performance of an HFRC cable,the AC loss and contact resistance of the HFRC prototype cable were measured at the University of Twente.The measurements were done in liquid helium(4.2 K)with AC magnetic fields,applied perpendicular to the cable's long axis.The AC loss was measured simultaneously by a calibrated gas flow calorimeter utilizing the helium boil-off method,and by the magnetization method using pick-up coils.For the applied test conditions,no coupling loss could be distinguished as a part of the overall AC loss.It is suggested that this might be explained by the shielding of the conductor interior from the applied magnetic field by the outer tape layer due to the high critical current density of the REBCO tape,leading to a high penetration field.
基金the National Key R&D Program of China(2017YFB0403200)the National Natural Science Foundation of China(No.51872327)。
文摘Pure phase Y_(3)Fe_(5)O_(12)(YIG)ceramic was successfully produced by tape-casting forming process and one-step solid-state sintering method.The activation energy for densification was calculated to be 183.81 kJ/mol.Pure YIG ceramic with a relative density as high as 99.8%was fabricated.The existence of O vacancy and Fe^(2+)ions was determined by XPS and EPR spectra.The RT saturation magnetization was measured to be 28.2 emu/g,and the hysteresis loss was calculated to be smaller than 10 mJ/kg in the temperature range of 230~360 K and be as high as 238.8 mJ/kg at 30 K.The dielectric loss tangent tanδ_(ε)was nearly zero at 6~7 GHz and 11~12 GHz.For complex permeability in the frequency range of 5~18 GHz,the magnetic loss tangent tanδ_(μ)fluctuated at around zero.Therefore,the low values of tanδ_(ε)and tanδ_(μ)indicate that it is a low loss ceramic material.
