About this publication
ISSN: 2772-8307
Copyright © 2026 Shanghai Jiaotong University. Published by Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.
cited:17
Geometric origin of intrinsic dark counts in superconducting nanowire single-photon detectors
-
Article Number:Article 100006
Article preview
Abstract
Corresponding email:lxyou@mail.sim.ac.cn
The dark count is one of the key physical issues for superconducting nanowire single-photon detectors (SNSPDs) that limits various applications for optical quantum information and classical optics. When the bias current approaches the switching current of SNSPDs, the dark count is actually dominated by the intrinsic dark counts (iDCs). However, the origin of iDCs and its relation to constrictions remains unclear for practical SNSPDs. We herein systematically characterize the iDCs of the SNSPDs with and without artificial geometric constrictions by applying the differential readout method. For these devices with constrictions, we have observed distinct Gaussian distributions in the temporal distribution of iDCs, in which the time difference between the distributions is consistent with the geometric distance between constrictions, and the rates of iDCs produced by each constriction are in good agreement with constrictions' widths. With respect to practical SNSPDs, surprisingly, we also observe several Gaussian distributions in the temporal domain and it shows no significant dependence on the devices’ sizes, demonstrating that the iDCs of SNSPDs are mainly dominated by a few specific constrictions.
cited:58
Effect of edge cracks on critical current degradation in REBCO tapes under tensile stress
-
Article Number:Article 100007
Article preview
Abstract
Corresponding email:tmqu@mail.tsinghua.edu.cn
The slitting process for manufacturing (REBCO, RE = Rare earth) tapes of required width significantly improves the production efficiency and reduces production costs. However, edge cracks induced by the slitting process of wide REBCO tapes may cause premature degradation under high tensile stress in high-field magnets. Therefore, it is necessary to evaluate the effect of edge cracks of REBCO tapes on the critical current () degradation. Firstly, degradation under artificial cracks was measured to validate the applicability of linear elastic fracture mechanics for the REBCO layer. The maximum circumferential stress criterion was used to derive the mixed-mode stress intensity factor of multiple oblique edge cracks. A semi-analytical model considering edge crack properties such as angle , spacing d, and length a, was built to evaluate the critical load and critical crack. We found that when the stress intensity factor at the crack tip is below , edge cracks did not propagate. We examined commercial REBCO tapes manufactured by two different processes, concluding that edge cracks in these tapes will not cause premature degradation.
cited:21
Multiphysics multilayer modelling and simulation of HTS REBCO magnets carrying direct currents under AC magnetic fields
-
Article Number:Article 100157
Article preview
Abstract
Corresponding email:jun.ma@bristol.ac.uk
High temperature superconducting homopolar inductor machine (HTS-HIM) is concerned and studied for electric aircraft because of its high power density, high efficiency, and high power-to-weight ratio. In an HTS-HIM, the high temperature superconducting magnets carrying DC currents under alternating background magnetic fields work as excitation magnets. Under extreme electromagnetic conditions, the voltage, loss, and temperature of the HTS magnets will increase because of the dynamic resistance effect. To predict the behaviors of the HTS magnet, it is necessary to analyze its electromagnetic-thermal characteristics by using a multiphysics model. This paper establishes a 2D axisymmetric multilayer multiphysics HTS magnet model based on the H-formulation. By using this multilayer multiphysics model, the electromagnetic-thermal characteristics of each turn can be analyzed. Meanwhile, this model can not only analyze the total loss and loss components of each layer under various operating conditions but also predict the temperature and quench behaviors of each part. The result shows that the loss components of the REBCO layer have distinct temperature dependence. When considering the thermal field effect, the magnetization loss of the REBCO layer reduces by 75% and the transport loss of the REBCO layer increases by 45% under high direct currents and high AC magnetic fields. Meanwhile, the temperature of the external turn is higher than the internal turn, and the external turn is at risk of quench in the operating process when the direct currents and AC magnetic fields are high. The multilayer multiphysics model is a powerful tool for designing, analyzing, and optimizing the HTS magnets in HTS-HIMs, and this multiphysics modelling technique can be utilized in modelling and simulating HTS REBCO magnets in various applications.
cited:2
Stress accommodation in nanoscale dolan bridges designed for superconducting qubits after critical failures
-
Article Number:Article 100158
Article preview
Abstract
Corresponding email:ctharri@sandia.gov
Josephson junctions are the principal circuit element in numerous superconducting quantum information devices and can be readily integrated into large-scale electronics. However, device integration at the wafer scale necessarily depends on having a reliable, high-fidelity, and high-yield fabrication method for creating Josephson junctions. When creating Al/AlO based superconducting qubits, the standard Josephson junction fabrication method relies on a sub-micron suspended resist bridge, known as a Dolan bridge, which tends to be particularly fragile and can often times fracture during the resist development process, ultimately resulting in device failure. In this work, we demonstrate a unique Josephson junction lithography mask design that incorporates stress-relief channels. Our simulation results show that the addition of stress-relief channels reduces the lateral stress in the Dolan bridge by more than 70% for all the bridge geometries investigated. In practice, our novel mask design significantly increased the survivability of the bridge during device processing, resulting in 100% yield for over 100 Josephson junctions fabricated.
cited:13
Hysteresis loss scaling of round REBCO cable towards 20 T
-
Article Number:Article 100165
Article preview
Abstract
Corresponding email:a.nijhuis@utwente.nl
High Temperature Superconductor (HTS) cables are considered for use in tokamaks such as DEMO (EU) and Chinese next generation fusion device (CN) or compact fusion machines. HTS cables offer the advantage of increased operating temperature and field strength of the magnet coils. In particular for Central Solenoid (CS) coils, the HTS high current cabled conductor windings are exposed to fast ramping AC magnetic fields inducing AC losses. The AC loss in HTS cables for fusion is mainly explored at low magnetic field amplitudes due to lack of testing facilities at higher fields. However, since the operating field in CS coils may be up to 20 T, it is essential to obtain quantitative knowledge on the AC losses for the entire applied field range with reasonable accuracy. This is important for thermohydraulic analysis of the operating temperature margin in coil designs. A method is used here to scale the hysteresis loss of a REBCO cable without transport current, measured up to only 1.4 T, to the entire field and temperature range up to 20 T and 50 K respectively. The field shielding and penetration effects of a multi-layer REBCO CORC®-like cable are quantified by measurements on stacked tape samples with a Vibrating Sample Magnetometer (VSM) up to fields significantly higher than the round cable’s full penetration field, found to be at 4.2 T. For higher fields, using measured critical current () data up to 19 T and an (B,T) scaling law for field (B) and temperature (T) serve to cover the required range of data within the window of coil operation parameters. Basic well-known theory on AC loss, particularly on the relation between hysteresis loss and critical current density against magnetic field, serves as a validation for this work.
Abstract
Corresponding email:yangwjbuaa@buaa.edu.cn; dz286@shu.edu.cn
Split pulsed magnets are widely employed in high temperature superconducting (HTS) motor armature winding as magnetizing coils to implement in-situ pulsed field magnetization (PFM) for HTS field pole magnets. We have designed and developed a compact and portable split pulsed magnet, that balances a peak central magnetic field of nearly 7 T and a rise time of 24 ms, making it particularly suitable for PFM of HTS materials at lower temperatures. Single and two-step PFM experiments of HTS GdBa 2Cu3O (GdBCO) bulk in different temperature ranges are conducted and the maximum trapped fields are observed to be T in the 40–50 K temperature range and nearly 4 T at 30 K in a 30 mm diameter GdBCO bulk. The trapped field results validate the excellent PFM ability of this designed split pulsed magnet and indicate a high trapped field (close to 4 T) can also be obtained in a coreless double armature. Moreover, multi-physical field responses of the split pulsed magnet during discharge are analyzed by a 3D field-circuit coupling model, which manifests that the split pulsed magnet is in a stable and safe operating state even under the highest charge voltage. Finally, this study may provide a novel clue for the development of coreless HTS bulk motors and suggest that HTS coreless motors can maintain a high air gap magnetic field while avoiding losses and thrust or torque fluctuations caused by iron core saturation under high magnetic fields.
Review