Pub Date : 2024-09-02DOI: 10.1088/1361-6668/ad6adb
Yu P Korneeva, M A Dryazgov, N V Porokhov, N N Osipov, M I Krasilnikov, A A Korneev, M A Tarkhov
We present a study of thin-film Mo resistors for NbN electronics operating at cryogenic temperatures. The key step is the 0.5–1.5 keV ion cleaning–activation of NbN before Mo deposition, which allows us to obtain a high-quality Mo/NbN interface. This, together with an additional Al bandage layer in the area of the contact pads, allows us to reduce the contact resistance below 1 Ω. The quality of the interfaces is confirmed by transmission electron microscopy and x-ray reflectometry.
我们介绍了一项关于在低温下工作的氮化铌电子薄膜钼电阻器的研究。关键步骤是在钼沉积之前对铌镍进行 0.5-1.5 keV 的离子清洗活化，从而获得高质量的钼/铌镍界面。透射电子显微镜和 X 射线反射仪证实了界面的质量。
{"title":"Molybdenum low-resistance thin-film resistors for cryogenic devices","authors":"Yu P Korneeva, M A Dryazgov, N V Porokhov, N N Osipov, M I Krasilnikov, A A Korneev, M A Tarkhov","doi":"10.1088/1361-6668/ad6adb","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6adb","url":null,"abstract":"We present a study of thin-film Mo resistors for NbN electronics operating at cryogenic temperatures. The key step is the 0.5–1.5 keV ion cleaning–activation of NbN before Mo deposition, which allows us to obtain a high-quality Mo/NbN interface. This, together with an additional Al bandage layer in the area of the contact pads, allows us to reduce the contact resistance below 1 Ω. The quality of the interfaces is confirmed by transmission electron microscopy and x-ray reflectometry.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-02DOI: 10.1088/1361-6668/ad70db
Raphael Unterrainer, Davide Gambino, Florian Semper, Alexander Bodenseher, Daniele Torsello, Francesco Laviano, David X Fischer, Michael Eisterer
Rare-earth-barium-copper-oxide based coated conductors exhibit a relatively low radiation robustness compared to e.g. Nb<sub>3</sub>Sn due to the <italic toggle="yes">d</italic>-wave symmetry of the order parameter, rendering impurity scattering pair breaking. The type and size of the introduced defects influence the degrading effects on the superconducting properties; thus the disorder cannot be quantified by the number of displaced atoms alone. In order to develop degradation mitigation strategies for radiation intense environments, it is relevant to distinguish between detrimental and beneficial defect structures. Gadolinium-barium-copper-oxide based samples irradiated with the full TRIGA Mark II fission reactor spectrum accumulate a high density of point-like defects and small clusters due to <italic toggle="yes">n</italic> - <italic toggle="yes">γ</italic> capture reactions of gadolinium. This leads to a 14–15 times stronger degradation of the critical temperature compared to samples shielded from slow neutrons. At the same time both irradiation techniques lead to the same degradation behavior of the critical current density as function of the transition temperature <inline-formula> <tex-math><?CDATA $J_{mathrm{c}} (T_{mathrm{c}})$?></tex-math><mml:math overflow="scroll"><mml:mrow><mml:msub><mml:mi>J</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant="normal">c</mml:mi></mml:mrow></mml:mrow></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant="normal">c</mml:mi></mml:mrow></mml:mrow></mml:msub><mml:mo stretchy="false">)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href="sustad70dbieqn1.gif"></inline-graphic></inline-formula>. Furthermore, annealing the degraded samples displayed the same <inline-formula> <tex-math><?CDATA $T_{mathrm{c}}$?></tex-math><mml:math overflow="scroll"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant="normal">c</mml:mi></mml:mrow></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href="sustad70dbieqn2.gif"></inline-graphic></inline-formula> recovery rates, indicating the universality of the defects responsible for the degradation. Since the primary knock on atom of the <italic toggle="yes">n</italic> - <italic toggle="yes">γ</italic> reaction as well as the recoil energy is known, we used molecular dynamics simulations to calculate which defects are formed in the neutron capture process and density functional theory to assess their influence on the local density of states. The defects found in the simulation were mainly single defects as well as clusters consisting of Oxygen Frenkel pairs, however, more complex defects such as Gd<inline-formula> <tex-math><?CDATA $ ^{mathrm{Cu}}$?></tex-math><mml:math overflow="scroll"><mml:mrow><mml:msup><mml:mrow></mml:mrow><mml:mrow><mml:mi>C</mml:mi><mml:mi>u</mml:mi></mml:mrow></mml:msup></mml:mrow></mml:math> <inline-graphic xlink:href="sustad70dbieqn3.gif"></inline-grap
由于阶次参数的 d 波对称性，稀土-钡-铜-氧化物涂层导体与 Nb3Sn 等涂层导体相比，辐射鲁棒性相对较低，这使得杂质散射对断裂。引入缺陷的类型和大小会影响超导性能的退化效应；因此，不能仅通过移位原子的数量来量化无序性。为了开发针对高辐射环境的降解缓解策略，区分有害和有益的缺陷结构具有重要意义。基于钆钡铜氧化物的样品经过 TRIGA Mark II 裂变反应堆全谱辐照后，由于钆的 n - γ 捕获反应，积累了高密度的点状缺陷和小团聚。与屏蔽慢中子的样品相比，这导致临界温度降低了 14-15 倍。同时，两种辐照技术都会导致临界电流密度随转变温度 Jc(Tc) 而发生相同的衰减。此外，退火降解样品显示出相同的 Tc 恢复率，这表明导致降解的缺陷具有普遍性。由于 n - γ 反应的主要撞击原子以及反冲能量是已知的，我们利用分子动力学模拟计算了中子俘获过程中形成的缺陷，并利用密度泛函理论评估了它们对局部态密度的影响。模拟中发现的缺陷主要是单缺陷以及由氧 Frenkel 对组成的簇，但也出现了更复杂的缺陷，如 GdCu 拮抗剂。
{"title":"Responsibility of small defects for the low radiation tolerance of coated conductors","authors":"Raphael Unterrainer, Davide Gambino, Florian Semper, Alexander Bodenseher, Daniele Torsello, Francesco Laviano, David X Fischer, Michael Eisterer","doi":"10.1088/1361-6668/ad70db","DOIUrl":"https://doi.org/10.1088/1361-6668/ad70db","url":null,"abstract":"Rare-earth-barium-copper-oxide based coated conductors exhibit a relatively low radiation robustness compared to e.g. Nb<sub>3</sub>Sn due to the <italic toggle=\"yes\">d</italic>-wave symmetry of the order parameter, rendering impurity scattering pair breaking. The type and size of the introduced defects influence the degrading effects on the superconducting properties; thus the disorder cannot be quantified by the number of displaced atoms alone. In order to develop degradation mitigation strategies for radiation intense environments, it is relevant to distinguish between detrimental and beneficial defect structures. Gadolinium-barium-copper-oxide based samples irradiated with the full TRIGA Mark II fission reactor spectrum accumulate a high density of point-like defects and small clusters due to <italic toggle=\"yes\">n</italic> - <italic toggle=\"yes\">γ</italic> capture reactions of gadolinium. This leads to a 14–15 times stronger degradation of the critical temperature compared to samples shielded from slow neutrons. At the same time both irradiation techniques lead to the same degradation behavior of the critical current density as function of the transition temperature <inline-formula>\u0000<tex-math><?CDATA $J_{mathrm{c}} (T_{mathrm{c}})$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>J</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:mrow></mml:msub><mml:mo stretchy=\"false\">(</mml:mo><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:mrow></mml:msub><mml:mo stretchy=\"false\">)</mml:mo></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad70dbieqn1.gif\"></inline-graphic></inline-formula>. Furthermore, annealing the degraded samples displayed the same <inline-formula>\u0000<tex-math><?CDATA $T_{mathrm{c}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad70dbieqn2.gif\"></inline-graphic></inline-formula> recovery rates, indicating the universality of the defects responsible for the degradation. Since the primary knock on atom of the <italic toggle=\"yes\">n</italic> - <italic toggle=\"yes\">γ</italic> reaction as well as the recoil energy is known, we used molecular dynamics simulations to calculate which defects are formed in the neutron capture process and density functional theory to assess their influence on the local density of states. The defects found in the simulation were mainly single defects as well as clusters consisting of Oxygen Frenkel pairs, however, more complex defects such as Gd<inline-formula>\u0000<tex-math><?CDATA $ ^{mathrm{Cu}}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msup><mml:mrow></mml:mrow><mml:mrow><mml:mi>C</mml:mi><mml:mi>u</mml:mi></mml:mrow></mml:msup></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad70dbieqn3.gif\"></inline-grap","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208397","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-29DOI: 10.1088/1361-6668/ad6e25
Mingyang Wang, Xuan’ang Meng, Xueliang Wang, Haosheng Ye, Xuan Zhou, Jie Sheng, Zhuyong Li, Zhijian Jin
Due to the critical current limitation of a single rare-earth barium copper oxide (REBCO) tape, stacking methods are generally employed to increase the current carrying capacity in practical high-temperature superconducting (HTS) applications. However, the overall critical current is strongly dependent on the self-magnetic field, which is influenced by the geometrical arrangement of conductors in the stack. Due to their brittle ceramic properties, REBCO tapes are conventionally bent along the thickness side of the tape. However, the difference in bending radii of the outer and inner tape surfaces in the stack may lead to fracture deformation, thereby limiting the stacking number of REBCO tapes. To balance the stacking number with the bending issue, a canted stack is proposed as a variant of the normal stack for REBCO tapes. As a potential HTS intermediate component, it is imperative to conduct a comprehensive study on the electromagnetic and thermal performance of the canted stack. The unique geometrical arrangement of the canted stack introduces new factors that affect the critical current and transport AC loss. This paper concludes with the special influencing factors of canted stacks, including canted angle, stacking number, tape width, and spatial structure. The metal interleaving method is introduced for spatial distribution changing and thermal stability. Furthermore, orthogonal analysis is performed to elucidate the comprehensive correlation among these multiple factors. This study provides insights into the overall critical current and transport AC loss for different combinations of canted stack and establishes a predicting function for critical current to support the structural design of canted stacks. Based on the specific case study, the improved capability of the canted stack is confirmed by both experiments and simulations.
{"title":"Electromagnetic and thermal performance study on a canted stack of REBCO tapes","authors":"Mingyang Wang, Xuan’ang Meng, Xueliang Wang, Haosheng Ye, Xuan Zhou, Jie Sheng, Zhuyong Li, Zhijian Jin","doi":"10.1088/1361-6668/ad6e25","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6e25","url":null,"abstract":"Due to the critical current limitation of a single rare-earth barium copper oxide (REBCO) tape, stacking methods are generally employed to increase the current carrying capacity in practical high-temperature superconducting (HTS) applications. However, the overall critical current is strongly dependent on the self-magnetic field, which is influenced by the geometrical arrangement of conductors in the stack. Due to their brittle ceramic properties, REBCO tapes are conventionally bent along the thickness side of the tape. However, the difference in bending radii of the outer and inner tape surfaces in the stack may lead to fracture deformation, thereby limiting the stacking number of REBCO tapes. To balance the stacking number with the bending issue, a canted stack is proposed as a variant of the normal stack for REBCO tapes. As a potential HTS intermediate component, it is imperative to conduct a comprehensive study on the electromagnetic and thermal performance of the canted stack. The unique geometrical arrangement of the canted stack introduces new factors that affect the critical current and transport AC loss. This paper concludes with the special influencing factors of canted stacks, including canted angle, stacking number, tape width, and spatial structure. The metal interleaving method is introduced for spatial distribution changing and thermal stability. Furthermore, orthogonal analysis is performed to elucidate the comprehensive correlation among these multiple factors. This study provides insights into the overall critical current and transport AC loss for different combinations of canted stack and establishes a predicting function for critical current to support the structural design of canted stacks. Based on the specific case study, the improved capability of the canted stack is confirmed by both experiments and simulations.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"9 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208398","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-29DOI: 10.1088/1361-6668/ad7173
Hongye Zhang
Featured by high power density and efficiency, high temperature superconducting (HTS) electric machines provide a promising solution to heavy-duty electric transport, e.g. electric aircraft. However, designing HTS machines, particularly high-speed HTS motors, presents significant challenges: (1) modelling is highly time-consuming due to the non-linear resistivity of superconductors and complex machine topology; (2) accurately estimating the AC loss of HTS windings remains an open aspiration due to the complicated AC environment. To reduce computational complexity, the thin film approximation (only considering the approximated 1-D HTS film) for HTS coated conductors (CCs) has been widely adopted in simulations, such as the T-formulation models; however, the thin film approximation becomes inadequate for HTS CCs under high-frequency magnetic fields, as encountered in high-speed motors for aerospace. To efficiently and accurately model the AC loss of HTS windings in high-speed superconducting machines, taking a 1 MW superconducting synchronous motor with HTS armature windings as an example, this paper has adopted a time-space extrusion (TSE) method, which demonstrates a >25-fold decrease in modelling time while maintaining comparable accuracy to two benchmark H-A models. The power dissipation in both normal-conducting and superconducting layers of HTS windings has been studied, the AC losses in different turns of the armature winding have been explored, and the slot leakage field harmonics have been illustrated. Results have shown that the losses in Cu and Ag layers for high-speed HTS machines operating at cryo-temperatures (e.g. liquid hydrogen temperature) are not neglectable, especially with a high residual resistance ratio and in the presence of harmonics. The HTS armature winding should be positioned away from the iron tooth and slot opening to minimise exposure to slot leakage fields. The adopted TSE modelling strategy and drawn conclusions have provided valuable insights for the efficient design of high-speed superconducting machines.
{"title":"Investigation of high-speed superconducting electric machines through time-space extrusion numerical modelling","authors":"Hongye Zhang","doi":"10.1088/1361-6668/ad7173","DOIUrl":"https://doi.org/10.1088/1361-6668/ad7173","url":null,"abstract":"Featured by high power density and efficiency, high temperature superconducting (HTS) electric machines provide a promising solution to heavy-duty electric transport, e.g. electric aircraft. However, designing HTS machines, particularly high-speed HTS motors, presents significant challenges: (1) modelling is highly time-consuming due to the non-linear resistivity of superconductors and complex machine topology; (2) accurately estimating the AC loss of HTS windings remains an open aspiration due to the complicated AC environment. To reduce computational complexity, the thin film approximation (only considering the approximated 1-D HTS film) for HTS coated conductors (CCs) has been widely adopted in simulations, such as the <bold>T</bold>-formulation models; however, the thin film approximation becomes inadequate for HTS CCs under high-frequency magnetic fields, as encountered in high-speed motors for aerospace. To efficiently and accurately model the AC loss of HTS windings in high-speed superconducting machines, taking a 1 MW superconducting synchronous motor with HTS armature windings as an example, this paper has adopted a time-space extrusion (TSE) method, which demonstrates a >25-fold decrease in modelling time while maintaining comparable accuracy to two benchmark <bold>H-A</bold> models. The power dissipation in both normal-conducting and superconducting layers of HTS windings has been studied, the AC losses in different turns of the armature winding have been explored, and the slot leakage field harmonics have been illustrated. Results have shown that the losses in Cu and Ag layers for high-speed HTS machines operating at cryo-temperatures (e.g. liquid hydrogen temperature) are not neglectable, especially with a high residual resistance ratio and in the presence of harmonics. The HTS armature winding should be positioned away from the iron tooth and slot opening to minimise exposure to slot leakage fields. The adopted TSE modelling strategy and drawn conclusions have provided valuable insights for the efficient design of high-speed superconducting machines.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"58 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208405","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We report the effect of hydrostatic pressure on LaO0.5F0.5Bi(S1−xSex)2 with chemical pressure applied to a conducting layer by means of electrical resistivity and ac-magnetic susceptibility measurements up to 2.5 GPa. We confirmed the bulk superconductive nature of the low superconducting (low-SC) and high superconducting (high-SC) phase using ac-magnetic susceptibility under hydrostatic pressure. The Tc of the high-SC phase was observed to decrease with an increase in the Se substitution. The critical pressure Pc shifted toward the higher P and the P-induced transition broadened with an increase in the Se content. The Tc of the low-SC phase can be expressed by assuming an applied hydrostatic pressure of 0.75 GPa as the Se substitution of x = 0.1. The broad Pc transition is likely to be ascribed to the inhomogeneity of the Se substitution.
我们报告了静水压力对 LaO0.5F0.5Bi(S1-xSex)2 的影响，通过电阻率和高达 2.5 GPa 的交流磁感应强度测量，对导电层施加化学压力。我们利用静水压力下的交流磁感应强度，证实了低超导（low-SC）和高超导（high-SC）相的体超导性质。观察到高超导相的 Tc 随 Se 取代量的增加而降低。临界压力 Pc 随 Se 含量的增加而向更高的 P 方向移动，P 诱导的转变也随之扩大。低碳酸钙相的 Tc 可以通过假设施加 0.75 GPa 的静水压力来表示，即 Se 的替代值为 x = 0.1。宽 Pc 过渡可能是由于硒替代的不均匀性造成的。
{"title":"Pressure tuning of the Se-substituted BiS2-based superconductor LaO0.5F0.5Bi(S 1−xSex )2","authors":"Naoki Kase, Katsuo Kondo, Shigefumi Watanabe, Nobuaki Miyakawa","doi":"10.1088/1361-6668/ad6e23","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6e23","url":null,"abstract":"We report the effect of hydrostatic pressure on LaO<sub>0.5</sub>F<sub>0.5</sub>Bi(S<inline-formula>\u0000<tex-math><?CDATA $ _{1-x}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mn>1</mml:mn><mml:msub><mml:mo>−</mml:mo><mml:mi>x</mml:mi></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad6e23ieqn2.gif\"></inline-graphic></inline-formula>Se<sub><italic toggle=\"yes\">x</italic></sub>)<sub>2</sub> with chemical pressure applied to a conducting layer by means of electrical resistivity and ac-magnetic susceptibility measurements up to 2.5 GPa. We confirmed the bulk superconductive nature of the low superconducting (low-SC) and high superconducting (high-SC) phase using ac-magnetic susceptibility under hydrostatic pressure. The <inline-formula>\u0000<tex-math><?CDATA $T_mathrm{c}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad6e23ieqn3.gif\"></inline-graphic></inline-formula> of the high-SC phase was observed to decrease with an increase in the Se substitution. The critical pressure <inline-formula>\u0000<tex-math><?CDATA $P_mathrm{c}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>P</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad6e23ieqn4.gif\"></inline-graphic></inline-formula> shifted toward the higher <italic toggle=\"yes\">P</italic> and the <italic toggle=\"yes\">P</italic>-induced transition broadened with an increase in the Se content. The <inline-formula>\u0000<tex-math><?CDATA $T_mathrm{c}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad6e23ieqn5.gif\"></inline-graphic></inline-formula> of the low-SC phase can be expressed by assuming an applied hydrostatic pressure of 0.75 GPa as the Se substitution of <italic toggle=\"yes\">x</italic> = 0.1. The broad <inline-formula>\u0000<tex-math><?CDATA $P_mathrm{c}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>P</mml:mi><mml:mrow><mml:mi mathvariant=\"normal\">c</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad6e23ieqn6.gif\"></inline-graphic></inline-formula> transition is likely to be ascribed to the inhomogeneity of the Se substitution.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"20 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208399","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-28DOI: 10.1088/1361-6668/ad70dc
Yue Wang, Xianghai Zhong, Junwen Zeng, Yinping Pan, Denghui Zhang, Shujie Yu, Ling Wu, Lu Zhang, Wei Peng, Jie Ren, Lei Chen, Zhen Wang
Superconducting memory cells that use flux quanta as their storage medium can achieve ultra-fast access times with ultra-low power consumption. However, the data signal generated by a flux quantum memory (FQM) cell is usually too weak and too fast to be measured directly. Here, we present a method to characterize the real-time operation of an FQM cell. The storage loop of the FQM cell, configured with a Nb/NbNX/Nb Josephson junction, was proven the capability to store multiple flux quanta. The readout was demonstrated by a superconducting quantum interference device composed of underdamped Nb/Al-AlOX/Nb Josephson junctions. The writing and reading operations were achieved by a short pulse ranging from 0.1 ns to 2.5 ns, and a constant bit error rate of ∼2.46% was measured for the fabricated FQM cell. The method presented here can be used to study real-time operation of an FQM cell in a direct manner.
{"title":"Characterization of high-speed writing and reading operations of the superconducting memory cell","authors":"Yue Wang, Xianghai Zhong, Junwen Zeng, Yinping Pan, Denghui Zhang, Shujie Yu, Ling Wu, Lu Zhang, Wei Peng, Jie Ren, Lei Chen, Zhen Wang","doi":"10.1088/1361-6668/ad70dc","DOIUrl":"https://doi.org/10.1088/1361-6668/ad70dc","url":null,"abstract":"Superconducting memory cells that use flux quanta as their storage medium can achieve ultra-fast access times with ultra-low power consumption. However, the data signal generated by a flux quantum memory (FQM) cell is usually too weak and too fast to be measured directly. Here, we present a method to characterize the real-time operation of an FQM cell. The storage loop of the FQM cell, configured with a Nb/NbN<italic toggle=\"yes\"><sub>X</sub></italic>/Nb Josephson junction, was proven the capability to store multiple flux quanta. The readout was demonstrated by a superconducting quantum interference device composed of underdamped Nb/Al-AlO<italic toggle=\"yes\"><sub>X</sub></italic>/Nb Josephson junctions. The writing and reading operations were achieved by a short pulse ranging from 0.1 ns to 2.5 ns, and a constant bit error rate of ∼2.46% was measured for the fabricated FQM cell. The method presented here can be used to study real-time operation of an FQM cell in a direct manner.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-28DOI: 10.1088/1361-6668/ad70dd
O A Nieves, K-H Müller
We numerically investigate the noise scaling in high-Tc commensurate 1D and 2D SQUID arrays. We show that the voltage noise spectral density in 1D arrays violates the scaling rule of ∼1/Np for the number Np of Josephson junctions in parallel. In contrast, in 2D arrays with Ns 1D arrays in series, the voltage noise spectral density follows more closely the expected scaling behaviour of ∼Ns/Np. Additionally, we reveal how the flux and magnetic field rms noise spectral densities deviate from their expected ∼(NsNp)−1/2 scaling and discuss their implications for designing low noise magnetometers.
{"title":"Noise scaling in SQUID arrays","authors":"O A Nieves, K-H Müller","doi":"10.1088/1361-6668/ad70dd","DOIUrl":"https://doi.org/10.1088/1361-6668/ad70dd","url":null,"abstract":"We numerically investigate the noise scaling in high-<italic toggle=\"yes\">T<sub>c</sub></italic> commensurate 1D and 2D SQUID arrays. We show that the voltage noise spectral density in 1D arrays violates the scaling rule of <inline-formula>\u0000<tex-math><?CDATA ${sim}1/N_p$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mrow><mml:mo>∼</mml:mo></mml:mrow><mml:mn>1</mml:mn><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:msub><mml:mi>N</mml:mi><mml:mi>p</mml:mi></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad70ddieqn1.gif\"></inline-graphic></inline-formula> for the number <italic toggle=\"yes\">N<sub>p</sub></italic> of Josephson junctions in parallel. In contrast, in 2D arrays with <italic toggle=\"yes\">N<sub>s</sub></italic> 1D arrays in series, the voltage noise spectral density follows more closely the expected scaling behaviour of <inline-formula>\u0000<tex-math><?CDATA ${sim}N_s/N_p$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mrow><mml:mo>∼</mml:mo></mml:mrow><mml:msub><mml:mi>N</mml:mi><mml:mi>s</mml:mi></mml:msub><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:msub><mml:mi>N</mml:mi><mml:mi>p</mml:mi></mml:msub></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad70ddieqn2.gif\"></inline-graphic></inline-formula>. Additionally, we reveal how the flux and magnetic field rms noise spectral densities deviate from their expected <inline-formula>\u0000<tex-math><?CDATA ${sim}(N_sN_p)^{-1/2}$?></tex-math><mml:math overflow=\"scroll\"><mml:mrow><mml:mrow><mml:mo>∼</mml:mo></mml:mrow><mml:mo stretchy=\"false\">(</mml:mo><mml:msub><mml:mi>N</mml:mi><mml:mi>s</mml:mi></mml:msub><mml:msub><mml:mi>N</mml:mi><mml:mi>p</mml:mi></mml:msub><mml:msup><mml:mo stretchy=\"false\">)</mml:mo><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math><inline-graphic xlink:href=\"sustad70ddieqn3.gif\"></inline-graphic></inline-formula> scaling and discuss their implications for designing low noise magnetometers.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"49 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208401","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-23DOI: 10.1088/1361-6668/ad68d2
Yang Liu, Yuanwen Gao
The second generation (2G) high-temperature superconducting (HTS) REBCO tape and the HTS cable made by the REBCO company are considered to be alternative materials for future superconducting magnet design due to their exceptional performance. The twisted stacked-tape slotted-core (TSSC) cable-in-conduit-conductor cable, which is one of the crucial layout structures in HTS cables, has been extensively studied by numerous research groups over the years. In this paper, a 3D finite element model of the TSSC HTS cable under bending and axial tensile loads is established using the bilinear isotropic hardening model in COMSOL commercial finite element software. The mechanical behavior of the TSSC cable under bending and axial tensile loads, as well as the evolution process of overall cable performance and critical current of individual tapes inside slots, are revealed by conducting mechanical analysis and using an empirical fitting formula between the critical current density of the 2G HTS tapes and axial strain. Furthermore, optimization engineering suggestions for its structure are provided, such as reducing the twist pitch, decreasing the tape width, increasing the number of tapes, reducing the slot width while avoiding direct contact between tapes and slot walls, increasing the number of slots, increasing diameter of diversion trench and inner diameter of helical core under predominant bending loads. In the case of axial tensile loads, the aforementioned suggestions are also applicable except for the inner and outer diameters of the helical core. The critical current performance can be enhanced by augmenting the outer diameter of the helical core in this case. However, it is almost unaffected by the inner diameter of the helical core.
{"title":"Mechanical behavior and critical current density variation of the twisted stacked-tape slotted-core cable-in-conduit conductor under bending and axial tensile load","authors":"Yang Liu, Yuanwen Gao","doi":"10.1088/1361-6668/ad68d2","DOIUrl":"https://doi.org/10.1088/1361-6668/ad68d2","url":null,"abstract":"The second generation (2G) high-temperature superconducting (HTS) REBCO tape and the HTS cable made by the REBCO company are considered to be alternative materials for future superconducting magnet design due to their exceptional performance. The twisted stacked-tape slotted-core (TSSC) cable-in-conduit-conductor cable, which is one of the crucial layout structures in HTS cables, has been extensively studied by numerous research groups over the years. In this paper, a 3D finite element model of the TSSC HTS cable under bending and axial tensile loads is established using the bilinear isotropic hardening model in COMSOL commercial finite element software. The mechanical behavior of the TSSC cable under bending and axial tensile loads, as well as the evolution process of overall cable performance and critical current of individual tapes inside slots, are revealed by conducting mechanical analysis and using an empirical fitting formula between the critical current density of the 2G HTS tapes and axial strain. Furthermore, optimization engineering suggestions for its structure are provided, such as reducing the twist pitch, decreasing the tape width, increasing the number of tapes, reducing the slot width while avoiding direct contact between tapes and slot walls, increasing the number of slots, increasing diameter of diversion trench and inner diameter of helical core under predominant bending loads. In the case of axial tensile loads, the aforementioned suggestions are also applicable except for the inner and outer diameters of the helical core. The critical current performance can be enhanced by augmenting the outer diameter of the helical core in this case. However, it is almost unaffected by the inner diameter of the helical core.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"25 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208402","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-22DOI: 10.1088/1361-6668/ad6e24
Yuwei Zhou, Zhen Huang
Constrained by the fabrication of second-generation high-temperature superconducting (2G HTS) tapes, connecting multiple pieces of tapes through joints is often necessary in large-scale applications. In the application of HTS magnets, joint technology is key for achieving closed-loop operation and reducing thermal loads. However, most soldered joints still cannot achieve the expected results. Thus, there is an urgent need to find a method for easily fabricating low-resistance joints. In this study, a low-resistance solder-free copper bonding joint for 2G HTS copper-plated tapes is proposed. The formation mechanism of the joint is presented, and the effects of the bonding temperature and pressure on the electrical and mechanical properties of the copper bonding joint are investigated. The results show that the copper bonding joint can be manufactured by pretreating the tape for 5 min and bonding it in the air for 3 min at 333 MPa at temperatures higher than (or equal to) 150 °C or at pressures greater than (or equal to) 250 MPa and 180 °C. The characteristic resistance of this joint is approximately 16.8 nΩ cm2, which is approximately one-third lower than that of soldered joints, and it has mechanical properties similar to those of soldered joints under axial tension. We believe that the application of this type of copper bonding joint can significantly aid in the design and manufacturing of large HTS magnets.
{"title":"A novel low-resistance solder-free copper bonding joint using a warm pressure welding method for REBCO coated conductors","authors":"Yuwei Zhou, Zhen Huang","doi":"10.1088/1361-6668/ad6e24","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6e24","url":null,"abstract":"Constrained by the fabrication of second-generation high-temperature superconducting (2G HTS) tapes, connecting multiple pieces of tapes through joints is often necessary in large-scale applications. In the application of HTS magnets, joint technology is key for achieving closed-loop operation and reducing thermal loads. However, most soldered joints still cannot achieve the expected results. Thus, there is an urgent need to find a method for easily fabricating low-resistance joints. In this study, a low-resistance solder-free copper bonding joint for 2G HTS copper-plated tapes is proposed. The formation mechanism of the joint is presented, and the effects of the bonding temperature and pressure on the electrical and mechanical properties of the copper bonding joint are investigated. The results show that the copper bonding joint can be manufactured by pretreating the tape for 5 min and bonding it in the air for 3 min at 333 MPa at temperatures higher than (or equal to) 150 °C or at pressures greater than (or equal to) 250 MPa and 180 °C. The characteristic resistance of this joint is approximately 16.8 nΩ cm<sup>2</sup>, which is approximately one-third lower than that of soldered joints, and it has mechanical properties similar to those of soldered joints under axial tension. We believe that the application of this type of copper bonding joint can significantly aid in the design and manufacturing of large HTS magnets.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142226525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-08-22DOI: 10.1088/1361-6668/ad68d3
Anang Dadhich, Philippe Fazilleau, Enric Pardo
High-field superconducting REBCO magnets contain several coils with many turns. For these magnets, electro-thermal quench is an issue that magnet designers need to take into account. Thus, there is a need for a fast and accurate software to numerically model the overall performance of full-scale magnets. High temperature superconductors can be modeled using different techniques for electro-magnetic and thermal (finite element method) analysis. However, it takes a lot of time to model the electro-magnetic and electro-thermal behavior of superconductors simultaneously, especially for non-insulated or metal-insulated coils. In addition, most of the available methods ignore screening currents, which are an important feature of REBCO magnets. We have developed a novel software programmed in C++, which performs coupled electro-magnetic and electro-thermal analysis using variational methods based on minimum electro-magnetic entropy production and finite difference, respectively. The developed software, which takes screening currents into account, is applied to axi-symmetric full scale magnets of more than 32 T field strength under the SuperEMFL project for thermal quench reliability during standard operation. We show that magnets incorporating non-insulated coils are more reliable against quench than metal insulated coils. Also, realistic cooling conditions at the boundaries are essential for such simulations. The model developed can be used for a quick and complete electro-magnetic and electro-thermal analysis of superconducting high field magnets.
高磁场超导 REBCO 磁体包含多个匝数很多的线圈。对于这些磁体，电热淬火是磁体设计人员需要考虑的一个问题。因此，需要一种快速、准确的软件来对全尺寸磁体的整体性能进行数值建模。高温超导体可以使用不同的电磁和热（有限元法）分析技术进行建模。然而，同时为超导体的电磁和电热行为建模需要大量时间，尤其是对于非绝缘或金属绝缘线圈。此外，大多数现有方法都忽略了屏蔽电流，而屏蔽电流是 REBCO 磁体的一个重要特征。我们用 C++ 开发了一种新颖的软件，分别使用基于最小电磁熵产生和有限差分的变分法进行电磁和电热耦合分析。所开发的软件将屏蔽电流考虑在内，并应用于超级电磁淬火磁场（SuperEMFL）项目中磁场强度超过 32 T 的轴对称全尺度磁体，以确保其在标准运行期间的热淬火可靠性。结果表明，与金属绝缘线圈相比，采用非绝缘线圈的磁体具有更高的抗淬火可靠性。此外，边界的实际冷却条件对于此类模拟也至关重要。所开发的模型可用于对超导高磁场磁体进行快速、全面的电磁和电热分析。
{"title":"A novel and fast electromagnetic and electrothermal software for quench analysis of high field magnets","authors":"Anang Dadhich, Philippe Fazilleau, Enric Pardo","doi":"10.1088/1361-6668/ad68d3","DOIUrl":"https://doi.org/10.1088/1361-6668/ad68d3","url":null,"abstract":"High-field superconducting REBCO magnets contain several coils with many turns. For these magnets, electro-thermal quench is an issue that magnet designers need to take into account. Thus, there is a need for a fast and accurate software to numerically model the overall performance of full-scale magnets. High temperature superconductors can be modeled using different techniques for electro-magnetic and thermal (finite element method) analysis. However, it takes a lot of time to model the electro-magnetic and electro-thermal behavior of superconductors simultaneously, especially for non-insulated or metal-insulated coils. In addition, most of the available methods ignore screening currents, which are an important feature of REBCO magnets. We have developed a novel software programmed in C++, which performs coupled electro-magnetic and electro-thermal analysis using variational methods based on minimum electro-magnetic entropy production and finite difference, respectively. The developed software, which takes screening currents into account, is applied to axi-symmetric full scale magnets of more than 32 T field strength under the SuperEMFL project for thermal quench reliability during standard operation. We show that magnets incorporating non-insulated coils are more reliable against quench than metal insulated coils. Also, realistic cooling conditions at the boundaries are essential for such simulations. The model developed can be used for a quick and complete electro-magnetic and electro-thermal analysis of superconducting high field magnets.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142208403","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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