This paper proposes the novel concept and method of the feed line resonator (FLR). By introducing the external quality factor adjusting line, the feed lines can be transformed to resonators, and can be used not only for providing external coupling, as well as generate extra transmission poles in the passband. The conditions for generating transmission poles by using the FLR are systematically investigated. The key advancement of the FLR method is that extra transmission poles are introduced, without increase the number of conventional resonators, the filter bandwidth can be extended and the selectivity also improved. The triple-mode FLR was proposed which can realize six extra transmission poles in the pass band and n transmission zeros out-of-band. A five-section multi-mode resonator proposed for wideband filter. Single-, two-, three- and four-stage wideband superconducting filters were designed to demonstrate the FLR method. These filters exhibit extreme sharp skirts, the attenuation slop at lower and higher band can reach 273.9 dB/GHz and 523.7 dB/GHz, respectively. The passband is from 2.26 GHz to 5.54 GHz with the FBW (fractional bandwidth) of 95 %. The measure results agree well with the simulated ones.
{"title":"The feed line resonator (FLR) method and it’s application to superconducting wideband filter design with extreme sharp skirt","authors":"Xilong Lu, Rui Zhang, Qingyu Kong, Shi-gang Zhou, Xudong Bai, Liguo Zhou, Guangsong Wei, Xueyang Fang","doi":"10.1088/1361-6668/ad5628","DOIUrl":"https://doi.org/10.1088/1361-6668/ad5628","url":null,"abstract":"\u0000 This paper proposes the novel concept and method of the feed line resonator (FLR). By introducing the external quality factor adjusting line, the feed lines can be transformed to resonators, and can be used not only for providing external coupling, as well as generate extra transmission poles in the passband. The conditions for generating transmission poles by using the FLR are systematically investigated. The key advancement of the FLR method is that extra transmission poles are introduced, without increase the number of conventional resonators, the filter bandwidth can be extended and the selectivity also improved. The triple-mode FLR was proposed which can realize six extra transmission poles in the pass band and n transmission zeros out-of-band. A five-section multi-mode resonator proposed for wideband filter. Single-, two-, three- and four-stage wideband superconducting filters were designed to demonstrate the FLR method. These filters exhibit extreme sharp skirts, the attenuation slop at lower and higher band can reach 273.9 dB/GHz and 523.7 dB/GHz, respectively. The passband is from 2.26 GHz to 5.54 GHz with the FBW (fractional bandwidth) of 95 %. The measure results agree well with the simulated ones.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":" 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141366314","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 : 2024-06-09DOI: 10.1088/1361-6668/ad55cf
D. Xi, Xinwei Cai, Qingyang Wang, Chen Guo, Li Li, Meng Song, Yan Zhang, Dongliang Wang, Yanwei Ma, Guo Yan, Furen Wang, Zizhao Gan
In this work, amorphous B coated Mg nanopowder (BCMN) is synthesized and the transport properties of MgB2 superconducting wire is significantly enhanced with different contents of BCMN. BCMN has high reactivity since it contains nanoscale Mg and amorphous B. It allows to obtain MgB2 nanocrystals at only 400 °C with the compression of a lattice parameter and expansion of c lattice parameters compared to MgB2 formed by micron-sized Mg mixed with amorphous B (Mg+B) powders. These MgB2 nanocrystals serve as crystal nuclei and promote the crystallization and growth of MgB2. The mismatch of different lattice parameters prepared using BCMN and M+B powders induces low angle grain boundaries (LAGBs) embedded in MgB2 grains. LAGB acts as plane defects, leading to a dominant surface pinning mechanism and an enhancement in the critical current density dependent on the magnetic field (J c(H)). At 4.2 K in 6 T, transport critical current density (J ct) of wire with 20 wt.% BCMN is 6.7×104 A·cm−2, approximately 1.8 times wire with 0 wt.% BCMN.
{"title":"Amorphous B coated Mg nanopowder induces low angle grain boundaries and enhances J\u0000 c of MgB2 wire","authors":"D. Xi, Xinwei Cai, Qingyang Wang, Chen Guo, Li Li, Meng Song, Yan Zhang, Dongliang Wang, Yanwei Ma, Guo Yan, Furen Wang, Zizhao Gan","doi":"10.1088/1361-6668/ad55cf","DOIUrl":"https://doi.org/10.1088/1361-6668/ad55cf","url":null,"abstract":"\u0000 In this work, amorphous B coated Mg nanopowder (BCMN) is synthesized and the transport properties of MgB2 superconducting wire is significantly enhanced with different contents of BCMN. BCMN has high reactivity since it contains nanoscale Mg and amorphous B. It allows to obtain MgB2 nanocrystals at only 400 °C with the compression of a lattice parameter and expansion of c lattice parameters compared to MgB2 formed by micron-sized Mg mixed with amorphous B (Mg+B) powders. These MgB2 nanocrystals serve as crystal nuclei and promote the crystallization and growth of MgB2. The mismatch of different lattice parameters prepared using BCMN and M+B powders induces low angle grain boundaries (LAGBs) embedded in MgB2 grains. LAGB acts as plane defects, leading to a dominant surface pinning mechanism and an enhancement in the critical current density dependent on the magnetic field (J\u0000 c(H)). At 4.2 K in 6 T, transport critical current density (J\u0000 ct) of wire with 20 wt.% BCMN is 6.7×104 A·cm−2, approximately 1.8 times wire with 0 wt.% BCMN.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":" 37","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141366811","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 : 2024-06-09DOI: 10.1088/1361-6668/ad55ce
Tomharu Yamauchi, N. Takeuchi, Nobuyuki Yoshikawa, Hao San, O. Chen
In this research, we unveil an innovative strategy in neuromorphic computing by developing a neuron model tailored for the energy-efficient Adiabatic Quantum-Flux-Parametron (AQFP) logic. This model is particularly aimed at enhancing neural network accelerators. Our design of the AQFP-based neuron operates effectively in both deterministic and non-deterministic modes. In deterministic mode, the design relies on superconducting inductive coupling to activate neurons by comparing the sum of AQFP signal currents against a tunable threshold. For non-deterministic operation, we demonstrate how altering specific circuit parameters can correlate these aggregated currents with the non-deterministic operational range of an AQFP current comparator. We verified its versatility and functionality by fabricating varied circuits and conducting extensive tests, confirming its practical application potential. Our work not only showcases the practical implementation of AQFP in neuromorphic computing but also sets a foundation for future advancements in energy-efficient AI hardware.
{"title":"Dual-mode neuron design with deterministic and non-deterministic operations using adiabatic superconductor devices","authors":"Tomharu Yamauchi, N. Takeuchi, Nobuyuki Yoshikawa, Hao San, O. Chen","doi":"10.1088/1361-6668/ad55ce","DOIUrl":"https://doi.org/10.1088/1361-6668/ad55ce","url":null,"abstract":"\u0000 In this research, we unveil an innovative strategy in neuromorphic computing by developing a neuron model tailored for the energy-efficient Adiabatic Quantum-Flux-Parametron (AQFP) logic. This model is particularly aimed at enhancing neural network accelerators. Our design of the AQFP-based neuron operates effectively in both deterministic and non-deterministic modes. In deterministic mode, the design relies on superconducting inductive coupling to activate neurons by comparing the sum of AQFP signal currents against a tunable threshold. For non-deterministic operation, we demonstrate how altering specific circuit parameters can correlate these aggregated currents with the non-deterministic operational range of an AQFP current comparator. We verified its versatility and functionality by fabricating varied circuits and conducting extensive tests, confirming its practical application potential. Our work not only showcases the practical implementation of AQFP in neuromorphic computing but also sets a foundation for future advancements in energy-efficient AI hardware.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":" 25","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141366784","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 : 2024-06-07DOI: 10.1088/1361-6668/ad558c
M. Abdioğlu, Gaurav Gautam, Min Zhang, Weijia Yuan
This paper presents a study of the current carrying capacity and AC loss of high-temperature superconducting (HTS) stacks to be used in busbar applications for all-electric aircraft. A 2D model was developed using COMSOL Multiphysics with a T-A formulation for detailed analysis. The study began by applying a stable 20 kA DC offset current to the HTS stacks, to simulate practical operating conditions. Firstly, the behaviour of the critical current was studied under self-field conditions for stacks with different number of HTS tapes and spacing. Secondly, AC ripple currents were introduced together with DC offsets and the effects of 3rd and 5th harmonic distortions (HD) were studied. The results show that configurations with 40 tapes and gaps of more than 2 mm are considered suitable for safe current transport under DC conditions. On the other hand, increasing the tape spacing leads to an increase in the safe transport current ripple, due to the reduced magnetic field interaction within the stack. In addition, the transport loss decreases as the air gap increases due to the reduction in the self-field, whereas it increases as the number of strips increases. The influence of the 3rd HD on the transport loss is minimal at a ripple current of 1% and slightly noticeable at 2%. However, it becomes more obvious as the ripple current approaches the critical value. Remarkably, even cases with equivalent total harmonic distortion (THD) show significantly higher transport losses when characterised by higher 5th HD than their counterparts with 3rd HD. This comprehensive analysis provides valuable information on the performance characteristics of HTS stacks in all-electric aircraft busbar applications and offers important insights for the development and optimisation of these systems in practical aerospace applications.
本文研究了高温超导 (HTS) 叠层在全电动飞机母线应用中的载流能力和交流损耗。使用 COMSOL Multiphysics 开发了一个二维模型，采用 T-A 公式进行详细分析。研究首先对 HTS 叠层施加稳定的 20 kA 直流偏置电流，以模拟实际运行条件。首先，研究了不同 HTS 磁带数量和间距的叠层在自场条件下的临界电流特性。其次，引入了交流纹波电流和直流偏移，并研究了三次和五次谐波失真（HD）的影响。结果表明，在直流条件下，40 条带、间距大于 2 毫米的配置适合于安全的电流传输。另一方面，增加磁带间距会导致安全传输电流纹波的增加，这是由于叠层内的磁场相互作用减少了。此外，由于自场的减少，传输损耗会随着气隙的增大而减小，而随着磁条数量的增加，传输损耗会增大。当纹波电流为 1%时，第 3 HD 对传输损耗的影响微乎其微，而当纹波电流为 2%时，这种影响则略微明显。然而，当纹波电流接近临界值时，这种影响变得更加明显。值得注意的是，即使是具有等效总谐波失真（THD）的情况，当第 5 HD 值高于第 3 HD 值时，其传输损耗也会明显高于第 3 HD 值。这项综合分析为全电动飞机母线应用中的 HTS 叠层性能特征提供了宝贵的信息，并为这些系统在实际航空应用中的开发和优化提供了重要的启示。
{"title":"AC transport loss analysis of HTS stack busbars for all-electric aircraft with harmonics and DC offset considerations","authors":"M. Abdioğlu, Gaurav Gautam, Min Zhang, Weijia Yuan","doi":"10.1088/1361-6668/ad558c","DOIUrl":"https://doi.org/10.1088/1361-6668/ad558c","url":null,"abstract":"\u0000 This paper presents a study of the current carrying capacity and AC loss of high-temperature superconducting (HTS) stacks to be used in busbar applications for all-electric aircraft. A 2D model was developed using COMSOL Multiphysics with a T-A formulation for detailed analysis. The study began by applying a stable 20 kA DC offset current to the HTS stacks, to simulate practical operating conditions. Firstly, the behaviour of the critical current was studied under self-field conditions for stacks with different number of HTS tapes and spacing. Secondly, AC ripple currents were introduced together with DC offsets and the effects of 3rd and 5th harmonic distortions (HD) were studied. The results show that configurations with 40 tapes and gaps of more than 2 mm are considered suitable for safe current transport under DC conditions. On the other hand, increasing the tape spacing leads to an increase in the safe transport current ripple, due to the reduced magnetic field interaction within the stack. In addition, the transport loss decreases as the air gap increases due to the reduction in the self-field, whereas it increases as the number of strips increases. The influence of the 3rd HD on the transport loss is minimal at a ripple current of 1% and slightly noticeable at 2%. However, it becomes more obvious as the ripple current approaches the critical value. Remarkably, even cases with equivalent total harmonic distortion (THD) show significantly higher transport losses when characterised by higher 5th HD than their counterparts with 3rd HD. This comprehensive analysis provides valuable information on the performance characteristics of HTS stacks in all-electric aircraft busbar applications and offers important insights for the development and optimisation of these systems in practical aerospace applications.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":" 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141372316","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 : 2024-06-06DOI: 10.1088/1361-6668/ad54f4
Yingyi Shao, Huiwu Wang, Minghui Niu, Wei Peng, Jie Ren, Zhen Wang
We performed a comprehensive investigation of the relationship between the maximum operating frequency of the NbN superconducting frequency divider and the key parameters of the NbN Josephson junction. We designed a superconducting frequency divider that uses a single NbN Josephson junction as a pulse generator, several NbN Josephson transmission lines (JTLs), an NbN Toggle Flip-flop (TFF), and a load. By comparing the bias voltage Vin of the pulse generator with the output voltage Vout of the load, we determined if the circuit was working correctly and calculated the maximum operating frequency fmax. Additionally, we employed JSICsim software for simulations to analyze the impact of key parameters of the NbN Josephson junction, such as critical current density Jc, gap voltage Vg, characteristic voltage Vc, quality factor Q, and specific capacitance Cs, on fmax. The simulation results demonstrate that fmax increases with increasing Jc and Q. Specifically when Jc exceeds 300 kA/cm2 and Q surpasses 4, the superconducting frequency divider can achieve a fmax of 1 THz. Furthermore, we successfully fabricated a superconducting frequency divider using a 10 kA/cm2 process and tested a fmax of 260 GHz, with a deviation of approximately 6% from the simulation results.
{"title":"The dependence of operating frequency of NbN toggle flip-flop on parameters of NbN josephson junctions","authors":"Yingyi Shao, Huiwu Wang, Minghui Niu, Wei Peng, Jie Ren, Zhen Wang","doi":"10.1088/1361-6668/ad54f4","DOIUrl":"https://doi.org/10.1088/1361-6668/ad54f4","url":null,"abstract":"\u0000 We performed a comprehensive investigation of the relationship between the maximum operating frequency of the NbN superconducting frequency divider and the key parameters of the NbN Josephson junction. We designed a superconducting frequency divider that uses a single NbN Josephson junction as a pulse generator, several NbN Josephson transmission lines (JTLs), an NbN Toggle Flip-flop (TFF), and a load. By comparing the bias voltage Vin of the pulse generator with the output voltage Vout of the load, we determined if the circuit was working correctly and calculated the maximum operating frequency fmax. Additionally, we employed JSICsim software for simulations to analyze the impact of key parameters of the NbN Josephson junction, such as critical current density Jc, gap voltage Vg, characteristic voltage Vc, quality factor Q, and specific capacitance Cs, on fmax. The simulation results demonstrate that fmax increases with increasing Jc and Q. Specifically when Jc exceeds 300 kA/cm2 and Q surpasses 4, the superconducting frequency divider can achieve a fmax of 1 THz. Furthermore, we successfully fabricated a superconducting frequency divider using a 10 kA/cm2 process and tested a fmax of 260 GHz, with a deviation of approximately 6% from the simulation results.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"144 7‐8","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141381283","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}
This paper reports an all REBCO (REBa2Cu3Ox, where RE=Y, Gd) superconducting magnet that generated a direct-current magnetic field of 26.86 T at 4.2 K in self-field, which is the highest magnetic field achieved by the high temperature superconducting (HTS) magnet. The magnet consists of a stack of 10 double pancake (DP) coils wound with two different width REBCO tapes, and the no-insulation (NI) winding technology was applied to increase its engineering current density. The inner and outer winding diameters and overall height of the magnet are 30 mm, 103.98 mm, and 102.6 mm, respectively. In order to control the stress risk in HTS magnet, the over-banding made of high elastic modulus stainless steel tapes was employed to the magnet. In addition, no obvious degradation was found in the performance of the magnet after quench at 26.86 T of 295.5 A. These test results demonstrate the great potential of REBCO magnets in high field applications.
{"title":"26.86-tesla direct-current magnetic field generated with an all-REBCO superconducting magnet","authors":"Xintao Zhang, Shuai Hu, Liang Guo, Wen Hong, Zhaoran Wang, Hong-jun Ma, Shuqing Zhang, J. Qin, Chao Zhou, Peng Gao, H. Jin, Liangjun Shao, Ti-Ming Qu, Zhiyong Hong, Fang Liu, Hua-jun Liu, Yuntao Song, Jiangang Li","doi":"10.1088/1361-6668/ad54f9","DOIUrl":"https://doi.org/10.1088/1361-6668/ad54f9","url":null,"abstract":"\u0000 This paper reports an all REBCO (REBa2Cu3Ox, where RE=Y, Gd) superconducting magnet that generated a direct-current magnetic field of 26.86 T at 4.2 K in self-field, which is the highest magnetic field achieved by the high temperature superconducting (HTS) magnet. The magnet consists of a stack of 10 double pancake (DP) coils wound with two different width REBCO tapes, and the no-insulation (NI) winding technology was applied to increase its engineering current density. The inner and outer winding diameters and overall height of the magnet are 30 mm, 103.98 mm, and 102.6 mm, respectively. In order to control the stress risk in HTS magnet, the over-banding made of high elastic modulus stainless steel tapes was employed to the magnet. In addition, no obvious degradation was found in the performance of the magnet after quench at 26.86 T of 295.5 A. These test results demonstrate the great potential of REBCO magnets in high field applications.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"73 s314","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141376577","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 : 2024-06-06DOI: 10.1088/1361-6668/ad4825
A Prudnikava, Y Tamashevich, A Makarova, D Smirnov, J Knobloch
In order to determine optimal parameters of vacuum thermal processing of superconducting radiofrequency niobium cavities exhaustive information on the initial chemical state of niobium and its modification upon a vacuum heat treatment is required. In the present work the chemical composition of the niobium surface upon ultra-high vacuum baking at 200 ∘C–400 ∘C similar to ‘medium-temperature baking’ and ‘furnace baking’ of cavities is explored in-situ by synchrotron x-ray photoelectron spectroscopy (XPS). Our findings imply that below the critical thickness of the Nb2O5 layer (≈1nm) niobium starts to interact actively with surface impurities, such as carbon and phosphorus. By studying the kinetics of the native oxide reduction, the activation energy and the rate-constant relation have been determined and used for the calculation of the oxygen-concentration depth profiles. It has been established that the controlled diffusion of oxygen is realized at temperatures 200 ∘C–300 ∘C, and the native-oxide layer represents an oxygen source, while at 400 ∘C the pentoxide is completely reduced and the doping level is determined by an ambient oxygen partial pressure. Fluorine (F to Nb atomic ratio is 0.2) after the buffered chemical polishing was found to be incorporated into the surface layer probed by XPS (≈4.6nm), and its concentration increased during the low-temperature baking (F/Nb = 0.35 at 230 ∘C) and depleted at higher temperatures (F/Nb = 0.11 at 400 ∘C). Thus, the influence of fluorine on the performance of mid-T baked, nitrogen-doped and particularly mild-baked (120 ∘C/48 h) cavities must be considered. The possible role of fluorine in the educed Nb<
{"title":"In-situ synchrotron x-ray photoelectron spectroscopy study of medium-temperature baking of niobium for SRF application","authors":"A Prudnikava, Y Tamashevich, A Makarova, D Smirnov, J Knobloch","doi":"10.1088/1361-6668/ad4825","DOIUrl":"https://doi.org/10.1088/1361-6668/ad4825","url":null,"abstract":"In order to determine optimal parameters of vacuum thermal processing of superconducting radiofrequency niobium cavities exhaustive information on the initial chemical state of niobium and its modification upon a vacuum heat treatment is required. In the present work the chemical composition of the niobium surface upon ultra-high vacuum baking at 200 <sup>∘</sup>C–400 <sup>∘</sup>C similar to ‘medium-temperature baking’ and ‘furnace baking’ of cavities is explored <italic toggle=\"yes\">in-situ</italic> by synchrotron x-ray photoelectron spectroscopy (XPS). Our findings imply that below the critical thickness of the <inline-formula>\u0000<tex-math><?CDATA $textrm{Nb}_2textrm{O}_5$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msub><mml:mtext>Nb</mml:mtext><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mtext>O</mml:mtext><mml:mn>5</mml:mn></mml:msub></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad4825ieqn1.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula> layer (<inline-formula>\u0000<tex-math><?CDATA ${approx}1textrm{nm}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mrow><mml:mo>≈</mml:mo></mml:mrow><mml:mn>1</mml:mn><mml:mtext>nm</mml:mtext></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad4825ieqn2.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>) niobium starts to interact actively with surface impurities, such as carbon and phosphorus. By studying the kinetics of the native oxide reduction, the activation energy and the rate-constant relation have been determined and used for the calculation of the oxygen-concentration depth profiles. It has been established that the controlled diffusion of oxygen is realized at temperatures 200 <sup>∘</sup>C–300 <sup>∘</sup>C, and the native-oxide layer represents an oxygen source, while at 400 <sup>∘</sup>C the pentoxide is completely reduced and the doping level is determined by an ambient oxygen partial pressure. Fluorine (F to Nb atomic ratio is 0.2) after the buffered chemical polishing was found to be incorporated into the surface layer probed by XPS (<inline-formula>\u0000<tex-math><?CDATA ${approx}4.6,textrm{nm}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:mrow><mml:mo>≈</mml:mo></mml:mrow><mml:mn>4.6</mml:mn><mml:mstyle scriptlevel=\"0\"></mml:mstyle><mml:mtext>nm</mml:mtext></mml:mrow></mml:math>\u0000<inline-graphic xlink:href=\"sustad4825ieqn3.gif\" xlink:type=\"simple\"></inline-graphic>\u0000</inline-formula>), and its concentration increased during the low-temperature baking (F/Nb = 0.35 at 230 <sup>∘</sup>C) and depleted at higher temperatures (F/Nb = 0.11 at 400 <sup>∘</sup>C). Thus, the influence of fluorine on the performance of mid-T baked, nitrogen-doped and particularly mild-baked (120 <sup>∘</sup>C/48 h) cavities must be considered. The possible role of fluorine in the educed <inline-formula>\u0000<tex-math><?CDATA $textrm{Nb}^{+5} rightarrow textrm{Nb}^{+4}$?></tex-math>\u0000<mml:math overflow=\"scroll\"><mml:mrow><mml:msup><mml:mtext>Nb</mml:mtext><mml:mrow><","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"65 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141524328","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}
Superconducting nanowire single-photon detectors (SNSPDs) have been widely applied in quantum information and deep-space exploration owing to their high detection efficiency, low dark count rate, and wide spectral response. In particular, the heat transfer in SNSPDs largely affects their performance parameters (e.g., quantum efficiency, count rates and recovery time), which can be modulated to optimize the performance and develop novel devices. Considering the potential of SNSPDs and the significance of heat transfer, the most recent progress toward understanding the mechanism and the modulation of heat transfer in SNSPDs is critically reviewed, with particular emphasis on the macroscopic correlation with device performance parameters and the microscopic analysis of existing theories, especially at interfaces. Furthermore, representative novel devices inspired by the need for heat transfer modulation in SNSPDs are discussed in detail. Finally, the development of heat transfer in SNSPDs is placed in perspective with the aim of highlighting future theoretical directions and practical applications.
{"title":"Heat transfer in superconducting nanowire single-photon detectors: mechanism and modulation","authors":"Wenlei Yin, Hao Wang, Xiaohan Wang, Rui Yin, Qi Chen, X. Jia, Huabing Wang, La-bao Zhang, Peiheng Wu","doi":"10.1088/1361-6668/ad54f2","DOIUrl":"https://doi.org/10.1088/1361-6668/ad54f2","url":null,"abstract":"\u0000 Superconducting nanowire single-photon detectors (SNSPDs) have been widely applied in quantum information and deep-space exploration owing to their high detection efficiency, low dark count rate, and wide spectral response. In particular, the heat transfer in SNSPDs largely affects their performance parameters (e.g., quantum efficiency, count rates and recovery time), which can be modulated to optimize the performance and develop novel devices. Considering the potential of SNSPDs and the significance of heat transfer, the most recent progress toward understanding the mechanism and the modulation of heat transfer in SNSPDs is critically reviewed, with particular emphasis on the macroscopic correlation with device performance parameters and the microscopic analysis of existing theories, especially at interfaces. Furthermore, representative novel devices inspired by the need for heat transfer modulation in SNSPDs are discussed in detail. Finally, the development of heat transfer in SNSPDs is placed in perspective with the aim of highlighting future theoretical directions and practical applications.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"7 18","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141380576","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 : 2024-06-06DOI: 10.1088/1361-6668/ad54f6
Jianfeng Huang, Y. Ilyin, Y. Zhai, H. T. Ten Kate, A. Nijhuis
The lap-type twin-box joints are integral components in ITER fusion magnets, with profound implications for magnet stability based on their electro-magnetic, thermal, and mechanical properties. Throughout the extensive R&D process, rigorous qualification tests are conducted to meet stringent standards. However, existing tests often prioritize global performance, which lack of strand-level details due to inherent limitations in test setups. Furthermore, as the referencing test facility of SULTAN falls short in replicating relevant ITER operating conditions, numerical methods that offer both accuracy and the requisite level of detail for comprehensive magnet and component analysis and development are necessary. This paper introduces the utilization of the JackPot-AC/DC code, developed at the University of Twente, as a fundamental tool for achieving strand-level precision in handling CICCs and joints, which encompasses copper and solder components. The primary focus of this study is to obtain precise input parameters, emphasizing their role in conducting a quantitative analysis using JackPot-AC/DC. The investigation centers on an ITER PF5 joint (PFJEU6), where contact resistances and AC losses were measured under parallel magnetic fields. Given the constraints in the measured results, an enhanced parameterization is performed to derive precise resistivity and solder-related parameters. Additionally, sensitivity analyses of individual parameters and cable compact configurations are thoughtfully evaluated. With the optimal input parameters acquired, systematic simulations of the joint exposed to transverse magnetic fields, mimicking SULTAN and ITER operating conditions, are processed and validated against experimental results. This research establishes a comprehensive foundation for the analysis of lap-type twin-box joints, including DC, AC, and stability properties. The outcomes will significantly contribute to advancing the understanding of the intricate behavior of these joints in the context of fusion magnet applications.
搭接式双箱接头是热核聚变实验堆聚变磁体中不可或缺的部件，其电磁、热和机械特性对磁体的稳定性有着深远的影响。在整个广泛的研发过程中，都要进行严格的鉴定测试，以满足严格的标准。然而，由于测试设置的固有限制，现有测试通常优先考虑整体性能，而缺乏磁链级细节。此外，由于 SULTAN 的参考测试设施在复制相关 ITER 运行条件方面存在不足，因此有必要采用既能提供准确性又能提供全面磁体和组件分析与开发所需的详细程度的数值方法。本文介绍了如何利用屯特大学开发的 JackPot-AC/DC 代码，将其作为在处理 CICC 和接头（包括铜和焊料元件）时实现股级精度的基本工具。本研究的主要重点是获得精确的输入参数，强调其在使用 JackPot-AC/DC 进行定量分析时的作用。调查以 ITER PF5 接头 (PFJEU6) 为中心，在平行磁场下测量接触电阻和交流损耗。考虑到测量结果的限制，进行了增强参数化，以得出精确的电阻率和焊料相关参数。此外，还对单个参数和电缆紧凑配置的敏感性进行了周到的评估分析。在获得最佳输入参数后，模拟 SULTAN 和 ITER 运行条件，对暴露在横向磁场中的接头进行了系统模拟，并根据实验结果进行了验证。这项研究为分析搭接式双箱接头（包括直流、交流和稳定性能）奠定了全面的基础。研究成果将极大地促进对聚变磁体应用中这些接头复杂行为的理解。
{"title":"Quantitative analysis of ITER Poloidal Field joints through rigorous resistivity parameterization","authors":"Jianfeng Huang, Y. Ilyin, Y. Zhai, H. T. Ten Kate, A. Nijhuis","doi":"10.1088/1361-6668/ad54f6","DOIUrl":"https://doi.org/10.1088/1361-6668/ad54f6","url":null,"abstract":"\u0000 The lap-type twin-box joints are integral components in ITER fusion magnets, with profound implications for magnet stability based on their electro-magnetic, thermal, and mechanical properties. Throughout the extensive R&D process, rigorous qualification tests are conducted to meet stringent standards. However, existing tests often prioritize global performance, which lack of strand-level details due to inherent limitations in test setups. Furthermore, as the referencing test facility of SULTAN falls short in replicating relevant ITER operating conditions, numerical methods that offer both accuracy and the requisite level of detail for comprehensive magnet and component analysis and development are necessary. This paper introduces the utilization of the JackPot-AC/DC code, developed at the University of Twente, as a fundamental tool for achieving strand-level precision in handling CICCs and joints, which encompasses copper and solder components. The primary focus of this study is to obtain precise input parameters, emphasizing their role in conducting a quantitative analysis using JackPot-AC/DC. The investigation centers on an ITER PF5 joint (PFJEU6), where contact resistances and AC losses were measured under parallel magnetic fields. Given the constraints in the measured results, an enhanced parameterization is performed to derive precise resistivity and solder-related parameters. Additionally, sensitivity analyses of individual parameters and cable compact configurations are thoughtfully evaluated. With the optimal input parameters acquired, systematic simulations of the joint exposed to transverse magnetic fields, mimicking SULTAN and ITER operating conditions, are processed and validated against experimental results. This research establishes a comprehensive foundation for the analysis of lap-type twin-box joints, including DC, AC, and stability properties. The outcomes will significantly contribute to advancing the understanding of the intricate behavior of these joints in the context of fusion magnet applications.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"17 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141376952","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 : 2024-06-06DOI: 10.1088/1361-6668/ad54f5
Jinxing Zheng, Jinxin Sun, Fei Liu, Xufeng Liu, Junyi Peng, Jiong Zhang, Chi Zhang, Lei Zhu, Xiaoliang Zhu, Chen Huang, Yuan Cheng, Dongdong Su
The global shift towards sustainable development and technological advancements has propelled the energy transition trend. Recognizing the substantial environmental impact of conventional commercial airplanes, there is a growing urgency to develop a sophisticated superconducting motor system for commercial aviation. The advent of high-temperature superconducting motors presents a transformative leap, offering significant advantages in power density and efficiency when compared to traditional motors. To validate the issues that future liquid-hydrogen superconducting electric airplanes may encounter, a kilowatt-class aerospace high-temperature superconducting motor is designed. Based on the requirements of airborne applications, critical parameters such as electromagnetic characteristics, operating characteristics, and AC losses have been analyzed. Furthermore, extensive research and testing have been conducted on the superconducting motor magnet, leading to the successful assembly of a prototype. The superconducting motor has a rated output power of 2.7 kW and a rated speed of 5000 rpm. Rigorous ground operation performance tests have also been conducted to ensure the feasibility and reliability of the motor in practical applications. Benefiting from the topological structure design, the superconducting motor has an excellent sealing performance at low temperatures. The superconducting motor can maintain low temperature and high vacuum for a long time, when the vacuum pump is removed and the liquid nitrogen inlet is closed after the motor is completely cooled. The culmination of these endeavors is the realization of a successful flight validation of an unmanned aerial vehicle equipped with a high-temperature superconducting motor, demonstrating a sustained flight of nearly one hour.
{"title":"Flight verification of cooling self-sustaining high-temperature superconducting motor","authors":"Jinxing Zheng, Jinxin Sun, Fei Liu, Xufeng Liu, Junyi Peng, Jiong Zhang, Chi Zhang, Lei Zhu, Xiaoliang Zhu, Chen Huang, Yuan Cheng, Dongdong Su","doi":"10.1088/1361-6668/ad54f5","DOIUrl":"https://doi.org/10.1088/1361-6668/ad54f5","url":null,"abstract":"The global shift towards sustainable development and technological advancements has propelled the energy transition trend. Recognizing the substantial environmental impact of conventional commercial airplanes, there is a growing urgency to develop a sophisticated superconducting motor system for commercial aviation. The advent of high-temperature superconducting motors presents a transformative leap, offering significant advantages in power density and efficiency when compared to traditional motors. To validate the issues that future liquid-hydrogen superconducting electric airplanes may encounter, a kilowatt-class aerospace high-temperature superconducting motor is designed. Based on the requirements of airborne applications, critical parameters such as electromagnetic characteristics, operating characteristics, and AC losses have been analyzed. Furthermore, extensive research and testing have been conducted on the superconducting motor magnet, leading to the successful assembly of a prototype. The superconducting motor has a rated output power of 2.7 kW and a rated speed of 5000 rpm. Rigorous ground operation performance tests have also been conducted to ensure the feasibility and reliability of the motor in practical applications. Benefiting from the topological structure design, the superconducting motor has an excellent sealing performance at low temperatures. The superconducting motor can maintain low temperature and high vacuum for a long time, when the vacuum pump is removed and the liquid nitrogen inlet is closed after the motor is completely cooled. The culmination of these endeavors is the realization of a successful flight validation of an unmanned aerial vehicle equipped with a high-temperature superconducting motor, demonstrating a sustained flight of nearly one hour.","PeriodicalId":21985,"journal":{"name":"Superconductor Science and Technology","volume":"140 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141376864","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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