Compact solid-state sources of terahertz (THz) radiation are being sought for sensing, imaging, and spectroscopy applications across the physical and biological sciences. We demonstrate that coherent continuous-wave THz radiation of sizable power can be extracted from intrinsic Josephson junctions in the layered high-temperature superconductor Bi2Sr2CaCu2O8. In analogy to a laser cavity, the excitation of an electromagnetic cavity resonance inside the sample generates a macroscopic coherent state in which a large number of junctions are synchronized to oscillate in phase. The emission power is found to increase as the square of the number of junctions reaching values of 0.5 microwatt at frequencies up to 0.85 THz, and persists up to ∼50 kelvin. These results should stimulate the development of superconducting compact sources of THz radiation.

http://absimage.aps.org/image/MAR08/MWS_MAR08-2007-004672.pdf

Emission of Coherent THz-Radiation from Superconductors.

This paper describes the present status of high temperature superconductors (HTS) and of bulk superconducting magnet devices, their use in bearings, in flywheel energy storage systems (FESS) and linear transport magnetic levitation (Maglev) systems. We report and review the concepts of multi-seeded REBCO bulk superconductor fabrication. The multi-grain bulks increase the averaged trapped magnetic flux density up to 40% compared to single-grain assembly in large-scale applications. HTS magnetic bearings with permanent magnet (PM) excitation were studied and scaled up to maximum forces of 10 kN axially and 4.5 kN radially. We examine the technology of the high-gradient magnetic bearing concept and verify it experimentally. A large HTS bearing is tested for stabilizing a 600 kg rotor of a 5 kWh/250 kW flywheel system. The flywheel rotor tests show the requirement for additional damping. Our compact flywheel system is compared with similar HTS–FESS projects. A small-scale compact YBCO bearing with in situ Stirling cryocooler is constructed and investigated for mobile applications. Next we show a successfully developed modular linear Maglev system for magnetic train operation. Each module levitates 0.25t at 10 mm distance during one-day operation without refilling LN2. More than 30 vacuum cryostats containing multi-seeded YBCO blocks are fabricated and are tested now in Germany, China and Brazil.

http://iopscience.iop.org/article/10.1088/0953-2048/25/1/014007/pdf

Superconductor bearings, flywheels and transportation

This manuscript reports on the recent progress and the remaining materials challenges in the development of coated conductors (CCs) for power applications and magnets, with a particular emphasis on the different initiatives being active at present in Europe. We first summarize the scientific and technological scope where CCs have been raised as a complex technology product and then we show that there exists still much room for performance improvement. The objectives and CC architectures being explored in the scope of the European project EUROTAPES are widely described and their potential in generating novel breakthroughs emphasized. The overall goal of this project is to create synergy among academic and industrial partners to go well beyond the state of the art in several scientific issues related to CCs’ enhanced performances and to develop nanoengineered CCs with reduced costs, using high throughput manufacturing processes which incorporate quality control tools and so lead to higher yields. Three general application targets are considered which will require different conductor architectures and performances and so the strategy is to combine vacuum and chemical solution deposition approaches to achieve the targeted goals. A few examples of such approaches are described related to defining new conductor architectures and shapes, as well as vortex pinning enhancement through novel paths towards nanostructure generation. Particular emphasis is made on solution chemistry approaches. We also describe the efforts being made in transforming the CCs into assembled conductors and cables which achieve appealing mechanical and electromagnetic performances for power systems. Finally, we briefly mention some outstanding superconducting power application projects being active at present, in Europe and worldwide, to exemplify the strong advances in reaching the demands to integrate them in a new electrical engineering paradigm.

/pdf/coated-conductors-for-power-applications-materials-1e6nsc3j8f.pdf

Coated conductors for power applications: materials challenges

https://bura.brunel.ac.uk/bitstream/2438/14401/3/FullText.pdf

Heat pipe based systems - Advances and applications

Superconducting technology applications in electric machines have long been pursued due to their significant advantages of higher efficiency and power density over conventional technology. However, in spite of many successful technology demonstrations, commercial adoption has been slow, presumably because the threshold for value versus cost and technology risk has not yet been crossed. One likely path for disruptive superconducting technology in commercial products could be in applications where its advantages become key enablers for systems which are not practical with conventional technology. To help systems engineers assess the viability of such future solutions, we present a technology roadmap for superconducting machines. The timeline considered was ten years to attain a Technology Readiness Level of 6+, with systems demonstrated in a relevant environment. Future projections, by definition, are based on the judgment of specialists, and can be subjective. Attempts have been made to obtain input from a broad set of organizations for an inclusive opinion. This document was generated Superconductor Science and Technology Supercond. Sci. Technol. 30 (2017) 123002 (41pp) https://doi.org/10.1088/1361-6668/aa833e Original content from this work may be used under the terms of the Creative Commons Attribution 3.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. 0953-2048/17/123002+41$33.00 © 2017 IOP Publishing Ltd Printed in the UK 1 through a series of teleconferences and in-person meetings, including meetings at the 2015 IEEE PES General meeting in Denver, CO, the 2015 ECCE in Montreal, Canada, and a final workshop in April 2016 at the University of Illinois, Urbana-Champaign that brought together a broad group of technical experts spanning the industry, government and academia.

https://iopscience.iop.org/article/10.1088/1361-6668/aa833e/pdf

High power density superconducting rotating machines—development status and technology roadmap

In order to further develop and verify the carrying capability and the curving performance of the high-temperature superconducting (HTS) maglev system, a new HTS maglev vehicle named “KENYON” was successfully developed at Southwest Jiaotong University (SWJTU), Chengdu, China, in December 2019. The maglev vehicle (2.9 m in length, 1.1 m in width) with a net levitation height of 10 mm was designed for 8 seated passengers which can run along a 45-m-long racetrack-type evacuated tube with a 2-m-diameter circular cross section. Compared with the previous maglev vehicle “Super-Maglev”, the “KENYON” vehicle decreases dead weight by 10%. Meanwhile, the amount of HTS bulks used in the “KENYON” is the same as that of the previous vehicle. By the efficient usage of the limited space of the ring line, it has the design characteristics of 67% low floor area of the whole vehicle which is convenient for the whole 8 passengers seating, getting on and getting off. Moreover, the curve passing performance of the vehicle is also specially improved by adjusting the running gear. This development of the new prototype strongly demonstrates the HTS maglev has the great potential of load capacity and curving performance for practical application.

The New High-Temperature Superconducting Maglev Vehicle Developed in ASCLab

The high temperature superconducting (HTS) maglev–evacuated tube transport (ETT) system is deemed as the next-generation transport system, with the potential to realize ultra-high speed. When the HTS maglev train travels inside the closed tube, it can cause serious aerodynamic thermal problems that affect the traffic safety. In this paper, a three-dimensional model and the Reynolds Average Navier-Stokes (RANS) based on SST k-ω turbulence model are used to study the aerodynamic thermal of the HTS maglev-ETT system. The numerical methods were verified by the wind tunnel experiment of the airfoil. The temperature distribution and aerodynamic thermal phenomena of the train and tube at different speeds were analyzed. The results show that the aerodynamic thermal of the HTS Maglev-ETT system is significantly affected by the speed. Due to the limitation of the annular space, the airflow is compressed in front of the head car and expanded near the tail car, making the temperature field more complex. The faster the train travels, the higher the average surface temperature of the train becomes. The shock wave will appear at a high speed, which further deteriorates the temperature field distribution of the system. These research results can provide a reference for the construction of the HTS Maglev-ETT system.

Numerical Study on the Influence of the Speed on the Aerodynamic Thermal in the HTS Maglev–Evacuated Tube Transport System

Turnouts are an important part of the engineering application of high-temperature superconducting (HTS) maglev. Compared with railway turnout, the strong magnetic force between segments of the permanent magnet guideway (PMG) used in the HTS maglev system makes it inconvenient to switch. By replacing part of the permanent magnets (PMs) at the turnout area, the switching magnetic poles with excitation can change the magnetic field distribution above the PMGs and guide the levitating HTS bulks to complete switching. This paper presents a novel turnout design that consists of switching magnetic poles and the attached permanent magnet device (PMD). In particular, the PMD can reduce the turnout volume and avoid coil heating. Based on the system, the simulation data indicates that the switching magnetic poles could replace PMs to create a similar magnetic field distribution, meanwhile feasible for design and manufacture. This work provides references for future design in non-mechanical PMGs turnouts.

A High-Temperature Superconducting Maglev Turnout Based on a Permanent Magnet Device

In order to promote the application of high temperature superconducting (HTS) maglev vehicle, the series of superconducting maglev (SCML) measurement devices — 01, 02 & 03 have been developed in Southwest Jiaotong University. During the course of research, the importance of three-dimensional (3D) study of the interaction between HTS bulks and permanent magnet guideways (PMGs) has become evident. More specifically, when the HTS vehicle is moving at a high speed, small irregularities of the PMG's magnetic field become the source of vibration. Therefore, in order to study the 3D force and the characteristics of HTS maglev under PMG irregularities, a new measurement device called SCML-05 was designed, constructed, and validated. This newly developed measurement device consists of two major parts. The first one is a closed-loop sliding platform providing 3D motion. The second part is measurement and data acquisition system with the software developed for this purpose. In addition, a laser displacement sensor is used to measure the geometry irregularities of the PMG. Overall, the SCML-05 is flexible and light. The force characteristics of the HTS bulks placed above the PMG can be precisely investigated by means of this system. Additionally, the PMG irregularities including geometry and magnetic field irregularities can be measured. These parameters are required to analyze the relationship between the PMG irregularities and the force of HTS maglev vehicle. The test process and typical results obtained by this system are presented in this paper.

The SCML-05 Developed for Studying the 3D Force and PMG Irregularities Characteristics of HTS Maglev

The utility model discloses a high-temperature superconducting magnetic levitated vehicle device which comprises a permanent magnet track (1), a levitated vehicle body, a low-temperature container (2) and one or a plurality of high-temperature superconducting block materials (3), the permanent magnet track (1) is made of permanent magnets, assembled magnetic materials and the like, the levitated vehicle body is arranged above the permanent magnet track (1), the low-temperature container (2) is fixedly arranged at the bottom of the levitated vehicle body, and the high-temperature superconducting block materials (3) are fixedly arranged in the low-temperature container The device is characterized in that seed crystal faces (3a) of the superconducting block materials (3) face the permanent magnet track (1), and one seed crystal growth boundary line (3b) of the seed crystal faces (3a) is consistent with the extending direction of the permanent magnet track (1) According to the superconducting magnetic levitated vehicle device, under the condition that any part and cost are not added, the stronger and more stable levitation performance can be obtained

Zigang Deng

Papers

The New High-Temperature Superconducting Maglev Vehicle Developed in ASCLab

Numerical Study on the Influence of the Speed on the Aerodynamic Thermal in the HTS Maglev–Evacuated Tube Transport System

A High-Temperature Superconducting Maglev Turnout Based on a Permanent Magnet Device

The SCML-05 Developed for Studying the 3D Force and PMG Irregularities Characteristics of HTS Maglev

High-temperature superconducting magnetic levitated vehicle device