Pub Date : 2024-07-14DOI: 10.1088/1361-6668/ad44e1
Rutian Huang, Yunfan Shi, Jianshe Liu and Wei Chen
A broadband on-chip multistage quantum amplifier (MQA) for reading out multiple superconducting qubits is proposed. The bandwidth of quantum amplifier is enhanced by concatenating amplifiers with modular nonreciprocal elements, which are superconducting isolators and circulators based on tunable inductor bridge. The circuit model of MQA is built and simulated. The variation of bandwidth, gain and gain-bandwidth product (GBP) of MQA with the number of stages and bandpass of the constitutive amplifiers are simulated. It is revealed that the bandwidth can be as large as ∼3.2 GHz with a gain of 20 dB at 4–8 GHz frequency range. For a 4-stage MQA composed of four quantum amplifiers with 20 dB gain and 0.3 GHz BW-pass, the bandwidth is 2.14 GHz at 20 dB gain, which is quite cost-efficient. Due to its non-reciprocity, MQA can effectively prevent signals from reflecting to quantum processors. In addition, MQA breaks the limitation of GBP and is easy to integrate with superconducting circuits. The MQA would play a crucial role in the high-fidelity readout of multiple qubits in large-scale superconducting quantum computers.
{"title":"Theoretical proposal for a broadband on-chip multistage quantum amplifier","authors":"Rutian Huang, Yunfan Shi, Jianshe Liu and Wei Chen","doi":"10.1088/1361-6668/ad44e1","DOIUrl":"https://doi.org/10.1088/1361-6668/ad44e1","url":null,"abstract":"A broadband on-chip multistage quantum amplifier (MQA) for reading out multiple superconducting qubits is proposed. The bandwidth of quantum amplifier is enhanced by concatenating amplifiers with modular nonreciprocal elements, which are superconducting isolators and circulators based on tunable inductor bridge. The circuit model of MQA is built and simulated. The variation of bandwidth, gain and gain-bandwidth product (GBP) of MQA with the number of stages and bandpass of the constitutive amplifiers are simulated. It is revealed that the bandwidth can be as large as ∼3.2 GHz with a gain of 20 dB at 4–8 GHz frequency range. For a 4-stage MQA composed of four quantum amplifiers with 20 dB gain and 0.3 GHz BW-pass, the bandwidth is 2.14 GHz at 20 dB gain, which is quite cost-efficient. Due to its non-reciprocity, MQA can effectively prevent signals from reflecting to quantum processors. In addition, MQA breaks the limitation of GBP and is easy to integrate with superconducting circuits. The MQA would play a crucial role in the high-fidelity readout of multiple qubits in large-scale superconducting quantum computers.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"46 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141720999","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 : 2024-07-11DOI: 10.1088/1361-6668/ad5c08
Richard T Ibekwe, Nicolò Riva, Dennis G Whyte, Vanessa J Sanchez and Zachary S Hartwig
High-temperature superconductor (HTS) cables and magnets are enabling a range of high-current and high-field applications, including compact fusion devices aiming to achieve net energy. Defects in HTS pose manufacturing, cost, and operational challenges. A rigorous understanding and predictive capability for defect-induced behavior at relevant scale has not been established. To address this shortcoming, we have developed a cable-level defect characterization experimental platform coupled to high-fidelity computational modeling. The cable ( 438 A at 77.4 K, self-field) comprises a non-twisted 70 cm-long copper former containing a soldered stack of five rare-earth barium copper oxide (REBCO) tapes (each with = 115.7 A/4 mm-w at 77.4 K, self-field), which can contain a variety of induced defects. Spatially-resolved electric fields are measured with a high-density voltage tap array and absolute current distribution with six custom-wound embedded Rogowski coils. 3D circuit modeling uses nodal analysis and self-consistently accounts for the magnetic field dependence of critical current. The model successfully predicts the experimentally measured spatial and operating current dependencies of electric field and current distribution with no defects, one defect, and two defects, validating the defect characterization platform as a tool for improving the design, cost, fabrication, and operation of REBCO cables.
高温超导体（HTS）电缆和磁体正在实现一系列大电流和高磁场应用，包括旨在实现净能量的紧凑型聚变装置。HTS 中的缺陷给制造、成本和运行带来了挑战。目前尚未建立起对相关规模的缺陷诱发行为的严格理解和预测能力。为了弥补这一不足，我们开发了一个电缆级缺陷表征实验平台，并结合了高保真计算建模。电缆（在 77.4 K 时为 438 A，自场）由一个 70 厘米长的非扭曲铜片组成，内含五条稀土氧化钡铜（REBCO）带的焊接堆叠（在 77.4 K 时，每条带 = 115.7 A/4 mm-w，自场），其中可能包含各种诱导缺陷。利用高密度电压抽头阵列测量空间分辨电场，利用六个定制绕制的嵌入式罗戈夫斯基线圈测量绝对电流分布。三维电路建模采用节点分析法，并自洽地考虑了临界电流的磁场依赖性。该模型成功预测了无缺陷、一个缺陷和两个缺陷时电场和电流分布的实验测量空间和工作电流依赖性，验证了缺陷表征平台作为改进 REBCO 电缆设计、成本、制造和运行的工具的有效性。
{"title":"A platform to study defect-induced behavior in high-temperature superconductor cables","authors":"Richard T Ibekwe, Nicolò Riva, Dennis G Whyte, Vanessa J Sanchez and Zachary S Hartwig","doi":"10.1088/1361-6668/ad5c08","DOIUrl":"https://doi.org/10.1088/1361-6668/ad5c08","url":null,"abstract":"High-temperature superconductor (HTS) cables and magnets are enabling a range of high-current and high-field applications, including compact fusion devices aiming to achieve net energy. Defects in HTS pose manufacturing, cost, and operational challenges. A rigorous understanding and predictive capability for defect-induced behavior at relevant scale has not been established. To address this shortcoming, we have developed a cable-level defect characterization experimental platform coupled to high-fidelity computational modeling. The cable ( 438 A at 77.4 K, self-field) comprises a non-twisted 70 cm-long copper former containing a soldered stack of five rare-earth barium copper oxide (REBCO) tapes (each with = 115.7 A/4 mm-w at 77.4 K, self-field), which can contain a variety of induced defects. Spatially-resolved electric fields are measured with a high-density voltage tap array and absolute current distribution with six custom-wound embedded Rogowski coils. 3D circuit modeling uses nodal analysis and self-consistently accounts for the magnetic field dependence of critical current. The model successfully predicts the experimentally measured spatial and operating current dependencies of electric field and current distribution with no defects, one defect, and two defects, validating the defect characterization platform as a tool for improving the design, cost, fabrication, and operation of REBCO cables.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"31 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141613691","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 : 2024-07-11DOI: 10.1088/1361-6668/ad6216
M. Marchevsky, S. Prestemon
Superconducting magnets of future fusion reactors are expected to rely on composite high-temperature superconductor (HTS) cable conductors. In presently used HTS cables, current sharing between components is limited due to poorly defined contact resistances between superconducting tapes or by design. The interplay between contact and termination resistances is the defining factor for power dissipation in these cables and ultimately defines their safe operational margins. However, the current distribution between components along the composite conductor and inside its terminations is a priori unknown, and presently, no means are available to actively tune current flow distribution in real-time to improve margins of quench protection. Also, the lack of ability to electrically probe individual components makes it impossible to identify conductor damage locations within the cable. In this work, we address both problems by introducing active current control of current distribution between components using cryogenically operated metal-oxide-semiconductor-field-effect transistors (MOSFETs). We demonstrate through simulation and experiments how real-time current controls can help to drastically reduce heat dissipation in a developing hot spot in a two-conductor model system and help identify critical current degradation of individual cable components. Prospects of other potential uses of MOSFET devices for improved voltage detection, AC loss-driven active quench protection, and remnant magnetization reduction in HTS magnets are also discussed.
{"title":"Quench protection for high-temperature superconductor cables using active control of current distribution","authors":"M. Marchevsky, S. Prestemon","doi":"10.1088/1361-6668/ad6216","DOIUrl":"https://doi.org/10.1088/1361-6668/ad6216","url":null,"abstract":"\u0000 Superconducting magnets of future fusion reactors are expected to rely on composite high-temperature superconductor (HTS) cable conductors. In presently used HTS cables, current sharing between components is limited due to poorly defined contact resistances between superconducting tapes or by design. The interplay between contact and termination resistances is the defining factor for power dissipation in these cables and ultimately defines their safe operational margins. However, the current distribution between components along the composite conductor and inside its terminations is a priori unknown, and presently, no means are available to actively tune current flow distribution in real-time to improve margins of quench protection. Also, the lack of ability to electrically probe individual components makes it impossible to identify conductor damage locations within the cable. In this work, we address both problems by introducing active current control of current distribution between components using cryogenically operated metal-oxide-semiconductor-field-effect transistors (MOSFETs). We demonstrate through simulation and experiments how real-time current controls can help to drastically reduce heat dissipation in a developing hot spot in a two-conductor model system and help identify critical current degradation of individual cable components. Prospects of other potential uses of MOSFET devices for improved voltage detection, AC loss-driven active quench protection, and remnant magnetization reduction in HTS magnets are also discussed.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"127 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141656816","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 : 2024-07-09DOI: 10.1088/1361-6668/ad5b25
Paul Nicaise, Jie Hu, Christine Chaumont, Piercarlo Bonifacio, Michel Piat, Hervé Geoffray, Faouzi Boussaha
We report on the experimental investigation of optical coupling for superconducting microresonators known as microwave kinetic inductance detectors (MKIDs) in the visible and near-infrared bands. MKIDs are photon-counting, time and energy-resolving detectors that still suffer from a poor quantum efficiency. To improve this efficiency, we propose to add a superconducting reflective layer below the absorbing part of the detector separated by a transparent Al2O3 layer with a quarter-wavelength thickness optimized around a single wavelength λ = 405 nm. We have first fabricated samples patterned from stoichiometric TiN (Tc∼4 K), one with the full optical stack, one without for reference and one with a partial optical stack in order to characterize the noise influence of each layer individually. We observe that the full optical stack geometry has the most impact on the resonator’s noise and quality factors. A second design was fabricated to characterize the optical response to short pulses of the optical stack and we show from both the frequential noise and optical response that a strong signature of TLS is still present in the optical stack sample. We have finally obtained single-photon response with the optical stack using a more sensitive tri-layer TiN/Ti/TiN absorber (Tc∼1.3 K) for which a maximum energy resolving power of R=E/ΔE∼ 1.3 was achieved using 405 nm laser pulses at 225 mK. The quality factors of both the reference and optical stack samples are similar but the frequency noise is still a tenfold higher for the optical stack sample which degrades the energy-resolving power of the detector.
{"title":"Noise analysis and optical response of microwave kinetic inductance detectors with an optical stack","authors":"Paul Nicaise, Jie Hu, Christine Chaumont, Piercarlo Bonifacio, Michel Piat, Hervé Geoffray, Faouzi Boussaha","doi":"10.1088/1361-6668/ad5b25","DOIUrl":"https://doi.org/10.1088/1361-6668/ad5b25","url":null,"abstract":"We report on the experimental investigation of optical coupling for superconducting microresonators known as microwave kinetic inductance detectors (MKIDs) in the visible and near-infrared bands. MKIDs are photon-counting, time and energy-resolving detectors that still suffer from a poor quantum efficiency. To improve this efficiency, we propose to add a superconducting reflective layer below the absorbing part of the detector separated by a transparent Al<sub>2</sub>O<sub>3</sub> layer with a quarter-wavelength thickness optimized around a single wavelength <italic toggle=\"yes\">λ</italic> = 405 nm. We have first fabricated samples patterned from stoichiometric TiN (<inline-formula>\u0000<tex-math><?CDATA $T_textrm{c} sim 4$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext></mml:msub><mml:mo>∼</mml:mo><mml:mn>4</mml:mn></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad5b25ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> K), one with the full optical stack, one without for reference and one with a partial optical stack in order to characterize the noise influence of each layer individually. We observe that the full optical stack geometry has the most impact on the resonator’s noise and quality factors. A second design was fabricated to characterize the optical response to short pulses of the optical stack and we show from both the frequential noise and optical response that a strong signature of TLS is still present in the optical stack sample. We have finally obtained single-photon response with the optical stack using a more sensitive tri-layer TiN/Ti/TiN absorber (<inline-formula>\u0000<tex-math><?CDATA $T_textrm{c} sim 1.3$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mi>T</mml:mi><mml:mtext>c</mml:mtext></mml:msub><mml:mo>∼</mml:mo><mml:mn>1.3</mml:mn></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad5b25ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> K) for which a maximum energy resolving power of <inline-formula>\u0000<tex-math><?CDATA $R = E/Delta E sim$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mi>R</mml:mi><mml:mo>=</mml:mo><mml:mi>E</mml:mi><mml:mrow><mml:mo>/</mml:mo></mml:mrow><mml:mi mathvariant=\"normal\">Δ</mml:mi><mml:mi>E</mml:mi><mml:mo>∼</mml:mo></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad5b25ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> 1.3 was achieved using 405 nm laser pulses at 225 mK. The quality factors of both the reference and optical stack samples are similar but the frequency noise is still a tenfold higher for the optical stack sample which degrades the energy-resolving power of the detector.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141574471","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 : 2024-07-09DOI: 10.1088/1361-6668/ad5c09
I V Yanilkin, A I Gumarov, I A Rudnev, L R Fatikhova, A G Kiiamov, A E Denisov, S A Khokhorin, D A Tayurskii and R G Batulin
This study presents the initial results of developing a technology for synthesizing a flexible superconducting magnesium diboride composite on a Hastelloy®-C276TM substrate coated with Al2O3/Y2O3/MgO/LaMnO3 buffer layers. The superconducting composite was deposited by magnetron sputtering from two Mg and B targets, followed by vacuum annealing at various substrate temperatures ranging from 400 °C to 700 °C. The superconducting transition temperature Tc ≈ 22 K, with a transition width ΔT ≈ 1 K, and critical current Jc ≈ 500 kA cm−2 (T= 5 K, H = 2 T) and Jc ≈ 11 kA cm−2 (T = 15 K, H = 2 T) at the optimal annealing temperature of 400 °C.
{"title":"Synthesis of MgB2 films on Hastelloy-C276 tape with Al2O3/Y2O3/MgO/LaMnO3 buffer layers by magnetron sputtering in co-evaporation mode","authors":"I V Yanilkin, A I Gumarov, I A Rudnev, L R Fatikhova, A G Kiiamov, A E Denisov, S A Khokhorin, D A Tayurskii and R G Batulin","doi":"10.1088/1361-6668/ad5c09","DOIUrl":"https://doi.org/10.1088/1361-6668/ad5c09","url":null,"abstract":"This study presents the initial results of developing a technology for synthesizing a flexible superconducting magnesium diboride composite on a Hastelloy®-C276TM substrate coated with Al2O3/Y2O3/MgO/LaMnO3 buffer layers. The superconducting composite was deposited by magnetron sputtering from two Mg and B targets, followed by vacuum annealing at various substrate temperatures ranging from 400 °C to 700 °C. The superconducting transition temperature Tc ≈ 22 K, with a transition width ΔT ≈ 1 K, and critical current Jc ≈ 500 kA cm−2 (T= 5 K, H = 2 T) and Jc ≈ 11 kA cm−2 (T = 15 K, H = 2 T) at the optimal annealing temperature of 400 °C.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"71 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141574470","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 : 2024-07-08DOI: 10.1088/1361-6668/ad603d
Tiantian Cai, Mingyang Wang, L. Hao, Xuan’ang Meng, Haolan Chen, Junjie Jiang, Jie Sheng, Zhijian Jin
The high aspect ratio of REBCO tapes has a significant impact on several characteristics in high-temperature superconducting (HTS) applications, like critical current and AC loss. Narrow filamentary technology can effectively reduce the impact of magnetic field dependence and enhance the electromagnetic performance of REBCO tapes. However, the existing methods are constrained by the trade-off between the narrow degree of REBCO filaments and high current capacity. Meanwhile, when processing REBCO tapes for large-scale magnets, there is a great possibility that local defects are lurking. A striated narrow-stacked structure is proposed based on the existing narrowing methods to address these challenges. To verify the validity of this structure, it is imperative to explore the non-uniform critical current and stacking effect on performance for multi-filament REBCO tapes with potential defects. This article introduces a magnetic extended network (MEN) model to analyze the electrical characteristics of striated narrow-stacked structures with different types of potential defects. Then, by coupling with a 3-D finite element method (FEM) electromagnetic module, the calculation results of the MEN model are visualized and used to analyze the electromagnetic characteristics including current sharing mechanism, magnetic field distribution, and critical current compensation due to stacking effect. It is found that stack structures successfully provide the performance remedy for multi-filament REBCO tapes with potential defects. This study aims to promote the narrowing improvement of REBCO tapes in high-field magnets and high-current applications.
{"title":"Non-uniform critical current and stacking effect remedy for multi-filament REBCO tapes with potential defects","authors":"Tiantian Cai, Mingyang Wang, L. Hao, Xuan’ang Meng, Haolan Chen, Junjie Jiang, Jie Sheng, Zhijian Jin","doi":"10.1088/1361-6668/ad603d","DOIUrl":"https://doi.org/10.1088/1361-6668/ad603d","url":null,"abstract":"\u0000 The high aspect ratio of REBCO tapes has a significant impact on several characteristics in high-temperature superconducting (HTS) applications, like critical current and AC loss. Narrow filamentary technology can effectively reduce the impact of magnetic field dependence and enhance the electromagnetic performance of REBCO tapes. However, the existing methods are constrained by the trade-off between the narrow degree of REBCO filaments and high current capacity. Meanwhile, when processing REBCO tapes for large-scale magnets, there is a great possibility that local defects are lurking. A striated narrow-stacked structure is proposed based on the existing narrowing methods to address these challenges. To verify the validity of this structure, it is imperative to explore the non-uniform critical current and stacking effect on performance for multi-filament REBCO tapes with potential defects. This article introduces a magnetic extended network (MEN) model to analyze the electrical characteristics of striated narrow-stacked structures with different types of potential defects. Then, by coupling with a 3-D finite element method (FEM) electromagnetic module, the calculation results of the MEN model are visualized and used to analyze the electromagnetic characteristics including current sharing mechanism, magnetic field distribution, and critical current compensation due to stacking effect. It is found that stack structures successfully provide the performance remedy for multi-filament REBCO tapes with potential defects. This study aims to promote the narrowing improvement of REBCO tapes in high-field magnets and high-current applications.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":" 8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141668340","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 : 2024-07-08DOI: 10.1088/1361-6668/ad59cf
F Adam, C Enss, S Kempf
Josephson tunnel junctions form the basis for various superconductor electronic devices. For this reason, enormous efforts are routinely taken to establish and later on maintain a scalable and reproducible wafer-scale manufacturing process for high-quality Josephson junctions. Here, we present an anodization-free fabrication process for Nb/Al-AlOx/Nb cross-type Josephson junctions that requires only a small number of process steps and that is in general intrinsically compatible with wafer-scale fabrication. We show that the fabricated junctions are of very high quality and, compared to other junction types, exhibit not only a significantly reduced capacitance but also an almost rectangular critical current density profile. Our process hence enables the usage of low capacitance Josephson junctions for superconductor electronic devices such as ultra-low noise dc-superconducting quantum interference devices (SQUIDs), microwave SQUID multiplexers based on non-hysteretic rf-SQUIDs and RFSQ circuits.
{"title":"Anodization-free fabrication process for high-quality cross-type Josephson tunnel junctions based on a Nb/Al-AlO x /Nb trilayer","authors":"F Adam, C Enss, S Kempf","doi":"10.1088/1361-6668/ad59cf","DOIUrl":"https://doi.org/10.1088/1361-6668/ad59cf","url":null,"abstract":"Josephson tunnel junctions form the basis for various superconductor electronic devices. For this reason, enormous efforts are routinely taken to establish and later on maintain a scalable and reproducible wafer-scale manufacturing process for high-quality Josephson junctions. Here, we present an anodization-free fabrication process for Nb/Al-AlO<sub>\u0000<italic toggle=\"yes\">x</italic>\u0000</sub>/Nb cross-type Josephson junctions that requires only a small number of process steps and that is in general intrinsically compatible with wafer-scale fabrication. We show that the fabricated junctions are of very high quality and, compared to other junction types, exhibit not only a significantly reduced capacitance but also an almost rectangular critical current density profile. Our process hence enables the usage of low capacitance Josephson junctions for superconductor electronic devices such as ultra-low noise dc-superconducting quantum interference devices (SQUIDs), microwave SQUID multiplexers based on non-hysteretic rf-SQUIDs and RFSQ circuits.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"48 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141574472","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 : 2024-07-08DOI: 10.1088/1361-6668/ad603e
Chunyan Li, Jin Zhou, Ling Zhao, Yanchang Zhu, R. Kang, Wei Li, Chengtao Wang, Yingzhe Wang, Juan Wang, Zhilong Hou, Rui Ma, Hongjun Zhang, Kai Liao, Xianping Zhang, Dongliang Wang, Fang Liu, Yanwei Ma, Qingjin Xu
The investigation of the behavior of normal zone propagation in iron-based superconducting (IBS) tapes is important for their application in magnets and the design of quench protection systems. However, little research has been done in this area. In this work, a conduction cooling test system for IBS tapes and coils has been built, which has functions such as charging test, temperature and voltage data acquisition, pulse current heating, quench detection and protection. A series of experiments were performed on several 27 cm long IBS tapes to measure their normal zone propagation velocity (NZPV). The variation trends of NZPV with different operating temperatures, and with different ratios of operating current to critical current were systematically explored. In addition, monitoring all the voltages between different positions of an IBS tape, including two joints, has provided more detailed results and findings.
{"title":"Investigation of normal zone propagation velocity in AgSn/Ag/Ba122 superconducting tapes using a conduction cooling test system","authors":"Chunyan Li, Jin Zhou, Ling Zhao, Yanchang Zhu, R. Kang, Wei Li, Chengtao Wang, Yingzhe Wang, Juan Wang, Zhilong Hou, Rui Ma, Hongjun Zhang, Kai Liao, Xianping Zhang, Dongliang Wang, Fang Liu, Yanwei Ma, Qingjin Xu","doi":"10.1088/1361-6668/ad603e","DOIUrl":"https://doi.org/10.1088/1361-6668/ad603e","url":null,"abstract":"\u0000 The investigation of the behavior of normal zone propagation in iron-based superconducting (IBS) tapes is important for their application in magnets and the design of quench protection systems. However, little research has been done in this area. In this work, a conduction cooling test system for IBS tapes and coils has been built, which has functions such as charging test, temperature and voltage data acquisition, pulse current heating, quench detection and protection. A series of experiments were performed on several 27 cm long IBS tapes to measure their normal zone propagation velocity (NZPV). The variation trends of NZPV with different operating temperatures, and with different ratios of operating current to critical current were systematically explored. In addition, monitoring all the voltages between different positions of an IBS tape, including two joints, has provided more detailed results and findings.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"116 2","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141666696","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 : 2024-07-04DOI: 10.1088/1361-6668/ad5f57
Yerzhan Mustafa, Keith Krause, Archit Shah, M. C. Hamilton, Selcuk Kose
Josephson-CMOS hybrid memory leverages the high speed and low power operation of single-flux quantum (SFQ) logic and the high integration densities of CMOS technology. One of the commonly used type of interface circuits in Josephson-CMOS memory is a Suzuki stack, which is a latching high-voltage driver circuit. Suzuki stack circuits are typically powered by an AC bias voltage that has several limitations such as synchronization and coupling effects. To address these issues, a novel DC-biased Suzuki stack circuit is proposed in this paper. As compared to a conventional AC-biased Suzuki stack circuit, the proposed DC-biased design can provide similar output voltage levels and parameter margins, approximately two times higher operating frequency, and three orders of magnitude lower heat load of bias cables.
{"title":"DC-biased suzuki stack circuit for Josephson-CMOS memory applications","authors":"Yerzhan Mustafa, Keith Krause, Archit Shah, M. C. Hamilton, Selcuk Kose","doi":"10.1088/1361-6668/ad5f57","DOIUrl":"https://doi.org/10.1088/1361-6668/ad5f57","url":null,"abstract":"\u0000 Josephson-CMOS hybrid memory leverages the high speed and low power operation of single-flux quantum (SFQ) logic and the high integration densities of CMOS technology. One of the commonly used type of interface circuits in Josephson-CMOS memory is a Suzuki stack, which is a latching high-voltage driver circuit. Suzuki stack circuits are typically powered by an AC bias voltage that has several limitations such as synchronization and coupling effects. To address these issues, a novel DC-biased Suzuki stack circuit is proposed in this paper. As compared to a conventional AC-biased Suzuki stack circuit, the proposed DC-biased design can provide similar output voltage levels and parameter margins, approximately two times higher operating frequency, and three orders of magnitude lower heat load of bias cables.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":" 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141678404","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 : 2024-07-04DOI: 10.1088/1361-6668/ad5b22
Yong Yang and Guolong Deng
Bulk high-temperature superconductors (HTSs) can trap high magnetic field and are potentially useful for a variety of applications as pseudo-permanent magnets. The pulsed field magnetization (PFM) for bulk HTSs is cost effective and flexible in application compared with quasi-static field cooling and zero field cooling techniques. Many PFM methods have been proposed in many studies to achieve the excellent magnetization performances such as high trapped field and large trapped magnetic flux. In order to clarify the magnetization characteristics of bulk HTSs using different typical PFM methods, we comparatively analyze several typical PFM methods using a simulation model based on the H-formulation combining the thermal conductivity equation. The electromagnetic and thermal behaviors during the magnetization of a bulk HTS with different PFM methods are numerically achieved using the solenoid-type coil to magnetize the bulk. The calculations show that multi-pulse magnetization methods can effectively enhance the trapped field and trapped magnetic flux of the bulk, and different multi-pulse magnetization methods have different efficiencies enhancing these performances. Among all considered PFM methods in the study, the combination method of modified multi-pulse technique with step-wise cooling and iteratively magnetizing pulsed-field method with reducing amplitude has the largest improvement for the trapped magnetic field and the trapped flux simultaneously.
{"title":"Comparative calculations of trapped field and trapped magnetic flux with different multi-pulse magnetization methods for a bulk high-temperature superconductor","authors":"Yong Yang and Guolong Deng","doi":"10.1088/1361-6668/ad5b22","DOIUrl":"https://doi.org/10.1088/1361-6668/ad5b22","url":null,"abstract":"Bulk high-temperature superconductors (HTSs) can trap high magnetic field and are potentially useful for a variety of applications as pseudo-permanent magnets. The pulsed field magnetization (PFM) for bulk HTSs is cost effective and flexible in application compared with quasi-static field cooling and zero field cooling techniques. Many PFM methods have been proposed in many studies to achieve the excellent magnetization performances such as high trapped field and large trapped magnetic flux. In order to clarify the magnetization characteristics of bulk HTSs using different typical PFM methods, we comparatively analyze several typical PFM methods using a simulation model based on the H-formulation combining the thermal conductivity equation. The electromagnetic and thermal behaviors during the magnetization of a bulk HTS with different PFM methods are numerically achieved using the solenoid-type coil to magnetize the bulk. The calculations show that multi-pulse magnetization methods can effectively enhance the trapped field and trapped magnetic flux of the bulk, and different multi-pulse magnetization methods have different efficiencies enhancing these performances. Among all considered PFM methods in the study, the combination method of modified multi-pulse technique with step-wise cooling and iteratively magnetizing pulsed-field method with reducing amplitude has the largest improvement for the trapped magnetic field and the trapped flux simultaneously.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"2014 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141548763","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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