cited:5

Superconducting nanostrip single photon detectors fabricated of aluminum thin-films

Article Number:Article 100096 Corresponding Author: Hui Zhou, Lixing You Author:Yuting Jiang, Xingyu Zhang, Hui Zhou, Xiaofu Zhang, Hao Li, Lixing You Article preview
Abstract
We systematically investigated the detection performance of Al nanostrips for single photons at various wavelengths. The Al films were deposited using magnetron sputtering, and the sophisticated nanostructures and morphology of the deposited films were revealed through high-resolution transmission electron microscopy. The fabricated Al meander nanostrips, with a thickness of 4.2 nm and a width of 178 nm, exhibited a superconducting transition temperature of 2.4 K and a critical current of approximately 5 μA at 0.85 K. While the Al nanostrips demonstrated a saturated internal quantum efficiency for 405-nm photons, the internal detection efficiency exhibited an exponential dependence on bias current without any saturation tendency for 1550-nm photons. This behavior can be attributed to the relatively large diffusion coefficient and coherence length of the Al films. By further narrowing the nanostrip width, the Al-SNSPDs remain capable of effectively detecting single telecom photons to facilitate practical applications.
Review
cited:49

Numerical modelling of electromechanical coupling behaviors in HTS coil with implementation of H formulation in FE software

Article Number:Article 100097 Corresponding Author: Huadong Yong Author:Huadong Yong, Dong Wei, Yunkai Tang, Donghui Liu Article preview
Abstract
(Re)Ba2Cu3O7-x (REBCO) coated conductors (CCs) have attracted considerable concern because of their outstanding current carrying capacity in magnetic fields of high strengths. A huge electromagnetic force is generated in the superconducting coil when conducting large currents in strong magnetic field. Thus, management of stress and strain has become a key technical challenge for the stability and safety of superconducting coil during operation. To accurately predict the electro-magnetic and mechanical characteristics of superconducting coil in strong magnetic field, an electromechanical model on the basis of the H-formulation and arbitrary Lagrangian-Eulerian (ALE) method is proposed here with FE software. To verify the proposed model, the simulation outcomes of the coil during magnetization are compared with the experimental outcomes. The coupling effect of magnet at high field strengths is dependent on the position of the coil. To reduce the screening current effect, the overshoot method with plateau is found superior to the traditional overshoot method, and an increase in the stabilization time can decrease the maximum value of stress. Finally, the electromechanical behaviors of single winding coil and two-tapes co-winding coil are compared.
Review
cited:3

Pressurization, intercalation, doping, and elements: An empirical study of superconductivity near perturbation onsets

Article Number:Article 100098 Corresponding Author: Shermane M. Benjamin Author:Shermane M. Benjamin Article preview
Abstract
Superconductivity is a phenomenon arising from cooperative electron behavior. However, correlations among (1) the minimum tuning parameter required for emergence, (2) the superconducting transition temperature resulting from minimal tuning, and (3) the host’s physical/chemical properties still elude the scientific community. Recent empirical investigations, such as those revealing ideal gas-like correlations at the onset of superconductivity in intercalated superconductors, motivate this study. Our investigation reports similar findings in systems (>170 compounds) exhibiting superconductivity through other perturbative means, such as single-element doping. In general, statistical measures, including distance correlation analyses (≠ linear regression fit) of thermodynamic variables, indicate the presence of empirical relationships near the superconducting onset of systematically tuned compounds. These relations involve unit cell volume (V), the number of valence electrons (N), and the superconducting transition temperature (Tc). Note: The author’s primary aim is not to validate or challenge BCS theory; it is instead to focus on leveraging methodology led by available data to enhance the exploration and development of innovative and cost-effective superconductors.
Review
cited:8

An energy-efficient 32-bit bit-parallel superconducting SFQ specialized processor

Article Number:Article 100099 Corresponding Author: Haihang You, Guangming Tang Author:Peiyao Qu, Huanli Liu, Xiangyu Zheng, Jiahong Yang, Liliang Ying, Jie Ren, Haihang You, Guangming Tang Article preview
Abstract
As the demand for energy efficiency rises, researchers are increasingly prioritizing the quest for energy-efficient chip design. Superconducting SFQ circuit technology has garnered attention due to its ultra-high speed and low power consumption characteristics. In this paper, we propose a layout method called Maximum Operating Frequency Constraint (MOFC) for SFQ circuit design. Using this method, we demonstrated a 32-bit bit-parallel string-matching processor fabricated based on SIMIT-Nb03P technology, which holds practical value. The MOFC method focuses on achieving high bit-width processor design within constrained area cost in SFQ circuits, contributing to less energy consumption. To the best of our knowledge, this represents the first demonstrated instance of a superconducting SFQ chip achieving successful internal 32-bit data parallel processing. Our chip has been fabricated and tested, revealing not only its capability for 32-bit bit-parallel processing at a high speed of 12 GHz but also its achievement of an energy efficiency ratio of up to 251 GOPS/W.
Review
cited:17

Cooling system for China’s 35 kV/2.2kA/1.2 km high-temperature superconducting cable achieves two-year successful operation

Article Number:Article 100100 Corresponding Author: Yunwu Han Author:Yunwu Han, Xihua Zong, Wei Xie Article preview
Abstract
In December 2021, a 1.2 km high-temperature superconducting (HTS) cable, Xuhui HTS Cable Project, was completed and installed in Xuhui district, Shanghai, China. A cooling system with three refrigerators and two liquid nitrogen (LN2) pumps was developed for this km-class cable. Now, this cooling system has worked successfully for two years without faults. This is a great progress for km-class HTS power cable technique, which is validating the reliability and commercial value of HTS power transmission.
Review
cited:18

Metallographic investigation of first full-size high-Jc Nb3Sn cable-in-conduit conductor after cyclic loading tests

Article Number:Article 100071 Corresponding Author: Chao Dai Author:Chao Dai, Yunhao Liu, Zichuan Guo, Yu Wu, Arend Nijhuis, Tianjun Xue, Zuojiafeng Wu, Jinggang Qin Article preview
Abstract
In order to verify the feasibility of applying high-Jc Nb3Sn strand in fusion magnet, a full-size cable-in-conduit conductor (CICC) with short twist pitch (STP) cable pattern was manufactured and tested in SULTAN facility at SPC, Switzerland. Three levels of cyclic electromagnetic (EM) load were applied on the sample stepwise, no visible decrease of current sharing temperature (Tcs) was observed until the EM load increased to 80 kA × 10.8 T, after that the Tcs decreased dramatically with the EM cycles, which suggested that irreversible deformation, causing a change in the strain state, or even damage has occurred in the superconducting strands. For investigating the reason which caused the conductor performance degradation, the tested conductor was dissected for metallographic observation. Eight segments which subjected to different EM loads were extracted from one of the legs, the geometric feature changes of the cable cross-sections were analyzed and compared. A good correlation was found between the decrease of the Tcs and deformation of the cable cross section. A mass of cracks were found on the sub-elements of strands in the segment which subjected to highest EM load, but the amount of crack is much lower in other segments. Combining the analyses, it is speculated that the critical EM load which causes irreversible degradation is between 850 kN/m and 870 kN/m for this conductor. The results could be a reference in high-Jc Nb3Sn CICC design.
Review
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