cited:57

Introduction of 35-kV kilometer-scale high-temperature superconducting cable demonstration project in Shanghai

Article Number:Article 100008 Corresponding Author: Xi Hua Zong Author:Xi Hua Zong, Yun Wu Han, Chong Qi Huang Article preview
Abstract
In December 2021, the 35-kV kilometer-level high-temperature superconducting (HTS) demonstration cable was officially connected to the grid in Xuhui District, Shanghai, China. A three-in-one HTS cable with a rated current of 2.2 kA, which replaces four-parallel lines XLPE cables, has been used in this project. This cable powers one of the busiest districts of Shanghai and serves to demonstrate and study the stability and reliability of a superconducting cable in the municipal power system. This project officially started in February 2019, and the type test of the prototype cable system was completed in November 2019. The commissioning test will be completed in November 2021. This paper introduces the main operating parameters, relevant research studies, and tests of this project.
Review
cited:12

Superconducting hot-electron bolometer mixers and their applications

Article Number:Article 100009 Corresponding Author: Wen Zhang Author:Wen Zhang, Wei Miao, Yuan Ren, Kang-Ming Zhou, Sheng-Cai Shi Article preview
Abstract
Superconducting hot electron bolometer (HEB) mixers are the most sensitive heterodyne detectors at frequencies beyond 1 THz, and are used for many astronomical observations. HEB, consisting of a narrow and short superconducting thin film patch connected to an antenna via contact pads, is brought into a highly sensitive operating regime by applying a DC current and a certain amount of local-oscillator power. Potentially, superconducting HEB mixers are capable of exhibiting high sensitivity for frequencies up to several tens of THz, as their output noise and conversion gain are nearly frequency independent according to the mixing mechanism. Moreover, the understanding of mixing mechanism has evolved over time from lumped-element model to distributed hot-spot model. In this review, we provide an overview of theoretical and experimental studies on HEBs and their applications, especially in astronomical observations on ground, airborne and space telescopes.
Review
cited:25

Progress in the development of the 122-type IBS wires

Article Number:Article 100010 Corresponding Author: Yanwei Ma Author:Xianping Zhang, Yanwei Ma Article preview
Abstract
Profit from their low anisotropy and high upper critical field, iron-based superconductors (IBSs) have great potential for high magnetic fields applications. Significant progress has been made for the current density improvement of (Sr,Ba)0.6K0.4Fe2As2 (122-type) IBS wires over the past fourteen years. In this article, an overview of the preparation procedures and key issues affecting the critical current performance of 122-type IBS wires is given, to provide a fundamental understanding of what controls the transport critical current density of 122-type IBS wires. Additionally, the recent developments for 122-type IBS wires are presented and future prospect and challenges in the development of 122-type IBS wires for practical applications are discussed.
Review
cited:8

A new LFSR based high-frequency test method for RSFQ circuit

Article Number:Article 100011 Corresponding Author: Minghui Niu, Jie Ren Author:Liyun Chen, Songrui Li, Liliang Ying, Minghui Niu, Huanli Liu, Hui Zhang, Xue Zhang, Xiaoping Gao, Jie Ren, Wei Peng, Zhen Wang Article preview
Abstract
Rapid single flux quantum (RSFQ) circuits have the advantages of high speed and low power consumption. The typical frequency of the RSFQ circuits is tens of GHz. Therefore, it is necessary to reliably test the high-frequency performance of RSFQ circuits simply and effectively. This paper proposes a new on-chip high-frequency testing method, which uses pseudo-random sequences generated by linear feedback shift register (LFSR) as the test vectors, and the output shift registers (SRs) to store the last piece of high-frequency testing result and read out it at low-frequency. Unlike the traditional high-frequency demonstration method of using the Input/Output SRs, our testing system can automatically generate a large number of test vectors to test the circuit at high frequency at low cost, making the whole high-frequency demonstration more reliable and convincing. On the other hand, this method is also a feasible and straightforward on-chip high-frequency test method for various RSFQ circuits. This work verified the proposed method, and the highest test frequency can reach 54 GHz while the circuit shows good operating margins.
Review
cited:13

Recent progress on high-temperature superconducting filters

Article Number:Article 100012 Corresponding Author: Liang Sun Author:Chi Zhang, Wei Xie, Chunguang Li, Jinhao Dai, Yuefeng Yuan, Runbo Jiang, Xu Wang, Jia Wang, Yun Wu, Liang Sun, Yusheng He Article preview
Abstract
Since the discovery of high temperature superconducting (HTS) materials in 1987, the performance of microwave filters such as insertion loss, selectivity, and out-band rejection has been significantly improved by utilizing HTS films. Nowadays, HTS filters have been widely used in wireless communications, space exploration, satellite communications, and several other fields. HTS filters with a special performance, such as wideband, dual-band or multiband, frequency tunable, and high power-handling capability have been designed and fabricated in recent years to meet the increasing requirements of practical applications and to further extend the application areas. This paper reviews the various types of above-mentioned HTS filters as well as the developments of novel design methodologies.
Review
cited:6

Cu/Ta sheaths for iron-based superconductors: First experimental findings in Ca/K-1144 wires

Article Number:Article 100014 Corresponding Author: Andrea Masi Author:Andrea Masi, Achille Angrisani Armenio, Andrea Augieri, Giuseppe Celentano, Anastasiya Duchenko, Alessandro Rufoloni, Angelo Vannozzi, Francesca Varsano, Antonio della Corte Article preview
Abstract
Iron based superconducting wires (IBSCs) produced by the Powder in Tube (PIT) method rely on the use of silver sheaths as chemical buffer between the outer metal and the superconducting core. The adoption of silver entails however some limitations, such as the viable temperature range when coupled with copper, and the incompatibility with calcium-based IBSCs already at 600 °C, driving the research towards other wires architecture. Taking inspiration from the low temperature superconductors field, we decided to evaluate the adoption of tantalum as diffusion barrier in a layered Cu/Ta architecture, choosing a Ca/K-1144 IBSC as case study considering the high reactivity issues already reported in the case of silver sheaths for this compound. Squared wires were produced through a groove rolling lamination process coupled with a thermal treatment at 800 °C. The microstructural analyses show the absence of interdiffusion between the different parts of the wire, and the magnetic characterization shows performance in line with similar polycrystalline manufacts, with margin of enhancement to be pursued via the optimization of the mechanical process and other experimental variables. The reported results suggest thus the effectiveness of tantalum as diffusion barrier for Ca/K-1144 PIT wires.
Review
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