The Gargantua test station is capable of delivering a direct current of 4800 A at a voltage of 10 V. It is designed for acquiring the dc voltage-current characteristic of high-temperature ...superconducting power cables operating at 77.3 K in liquid nitrogen. The goal is to estimate their critical current. The standardization of this dc characterization is a prerequisite for the adoption of this promising technology by power grid operators. This document reports on the experimental setup and the subsequent measurements carried out on a high-temperature superconducting power cable manufactured by Sumitomo and tested as part of the international round robin test for the IEC Technical Committee 90 Superconductivity.
We present direct detection constraints on the absorption of hidden-photon dark matter with particle masses in the range 1.2-30 eV c^{-2} with the DAMIC experiment at SNOLAB. Under the assumption ...that the local dark matter is entirely constituted of hidden photons, the sensitivity to the kinetic mixing parameter κ is competitive with constraints from solar emission, reaching a minimum value of 2.2×10^{-14} at 17 eV c^{-2}. These results are the most stringent direct detection constraints on hidden-photon dark matter in the galactic halo with masses 3-12 eV c^{-2} and the first demonstration of direct experimental sensitivity to ionization signals <12 eV from dark matter interactions.
The last bending section of a proton therapy beam line may be mounted on a rotating gantry to target the cancerous cells of patients from all possible angles. To gain such capability, it is sensible ...to use superconducting magnets because of their high energy density providing a large reduction in weight. In the following work, a configuration of combined function magnets for rotating gantries is presented. It includes two conventional electromagnets and three superconducting magnets using Nb 3 Sn conduction-cooled at around 4.2 K. For such assembly, an alignment procedure is proposed to ensure that a large beam momentum acceptance can be achieved. Besides this proposal, additional 3D mechanical Finite Element analyses were conducted to check that the structural support of the most critical superconducting magnets made of Nb 3 Sn wires and their coil thermal shields could handle their weight as well as the momentum due to the rotation.
Abstract High-temperature superconductors (HTS) are greatly appealing for the development of high efficient, and high energy density power devices. They are particularly relevant for applications ...requiring light and compact machines such as wind power generation. In this context, to ensure the proper design of the superconducting machines and their reliable operation in power systems, it is then important to develop models that can accurately include their physics but also can describe properly their interaction with the system. To achieve such a goal, one approach is the co-simulation. This numerical technique can bring fine geometrical and physical details of the machines through a finite element model (FEM) meanwhile dealing with the operation of the whole system that incorporates the machine and a subset of the power grid represented by an external electrical circuit. The goal of the present work is to put to use this numerical technique when superconducting components are involved. Here, a case study is proposed involving a 15 MW hybrid superconducting synchronous generator (HTS rotor and conventional stator) coupled to a direct current network via a rectifier and its associated filter. The case study related to wind power application allows grasping the technical issues when employing co-simulation dealing with HTS machines. The FEM of the generator is done in the commercial software COMSOL Multiphysics, which interacts with the circuit simulator Simulink through the built-in Functional Mock-up Unit. For the present study, a new version of the latest J – A formulation combined with homogenization technique is introduced allowing an even faster computation time compared to the T – A formulation. Distributed variables and global variables such as current density, magnetic flux density, and local losses for the former and voltage, current, electromagnetic torque, and power quality for the latter are estimated and compared for both formulations. The idea is to find the best-suited combination FEM-circuit under criteria of computational speed, accuracy, and numerical stability. Thus, it is shown that all formulations generate an error of less than 5% on the machine parameters and that the J – A formulation with first order elements stands out with a significant 4-fold reduction in computational costs.
The present work addresses the ongoing development of a mesh-based magnetic equivalent circuit (MEC) to estimate the magnetic flux distribution in a superconducting hybrid rotating synchronous ...machine, superconducting (SC) rotor, and conventional stator. The MEC is to be integrated in an existing thermoelectric lumped-parameter machine model for the transient simulation of High Temperature Superconductor (HTS) field coil synchronous generator (SG) in the dq0 frame of reference. It will allow the inclusion of the magnetic flux density inside the definition of the non-linear resistance of the superconductor in addition to the already-present temperature and current. The objective is to gain further accuracy on the coupled thermal and electromagnetic behavior of superconducting hybrid machines during partial or total loss of the superconducting state. In the present work, the MEC is benchmarked against a Finite Element Model (FEM). It is shown that the MEC can provide proper magnitude of the magnetic flux density over the HTS winding achieving a good estimation of the magnetic response of the field winding by taking into account the penetration of current within the superconductor. The case study is a 100-MVA hydroelectric HTS field coil SG considering a field current ramp.
Stability issues exist in embedded electrical grids, mainly due to power electronics. One of the solutions is to use a superconducting power filter (SPF), made of a non-inductive superconducting ...coil. The DC losses are close to zero, the coil being in its superconducting state. The AC losses, proportional to the frequency, are weak but still exist and can be used to increase the stability of the DC grid. In this paper, different SPF prototypes are presented and experimental characterizations are exposed: measurements of the critical current, measurements of AC losses and measurements of AC+DC losses. This AC+DC loss measurement is unusual, tricky and especially developed for SPF application. Experimental results are discussed and compared to calculations obtained with the analytical Norris formulas. Strip model formula underestimates losses and elliptical section formula overestimates losses but both formulas give good approximation of the losses and are therefore useful tools to design a SPF.
In the present work, the impact that the longitudinal shape of channels has on the current produced in the flow of a magneto-hydrodynamic microgenerator (MHDMG) is studied. The goal is to find the ...micro-channel geometry via modeling to maximize the current output for low Reynolds and Mach regimes. To carry out this study, a 3D dynamic numerical tool relying on the finite volume method was handled with the open-source software OpenFOAM. It is the base model to study the impact of intricate geometries on the ability to produce energy. An additional steady-state 2D analytical model was also developed to check some basic modeling assumptions. Both models have been experimentally validated on the simplest flow system having a constant square cross-section throughout. The results produced by both models cross-check very well and compare favorably with respect to experimental data. Hence, using the validated numerical tool, three shapes have been further investigated, namely, progressive (linear decrease of the cross-section), arc (parabolic decrease of the cross-section), and wavy (sinusoidal shape). It was found that the arc channel provides the greatest current output for the same volumetric flow. It is therefore the preferred choice for developing high current gain and more efficient MHDMG used in micro-scaled actuators and sensors.
•The current depends critically on the axial shape of the channel.•Axially arched shapes produce the highest currents in the fluid.•Currents can be conveniently focalized with wavy patterned shapes.•Currents increase linearly with the flow rate for all geometries.
Electric dipole moments (EDMs) of fundamental particles violate time invariance and the combined symmetry of charge and parity (CP). The existence of a large muon EDM (muEDM) is made plausible by ...tensions with Standard Model predictions for semileptonic decays of heavy meson measured at LHCb, BaBar, and Belle, as well as the muon’s anomalous magnetic moment (AMM). A discovery of the muEDM would manifest CP and lepton flavor universality (LFU) violation, revealing physics beyond the SM (BSM). The most sensitive muEDM search to date provides an upper limit of 1.8 × 10
−19
e
cm (CL 95%), extracted from high-precision data collected to measure the muon AMM. At the Paul Scherrer Institute, we are setting up a dedicated search for the muEDM using, for the first time, the frozen-spin technique to target an ultimate sensitivity better than 6 × 10
−23
e
cm. This novel technique increases the sensitivity to EDM-induced spin precession by cancelling the AMM-induced precession with the application of a precisely tuned electric field perpendicular to the muon momentum and the magnetic field. In this configuration, the dominant source of precession is the EDM coupling to the large relativistic electric field in the muon rest frame, generated by its motion in a strong 3 T uniform magnetic field. In a precursor experiment, we will apply the frozen-spin technique in a compact solenoid demonstrating a sensitivity of better than 3 × 10
−21
e
cm, probing uncharted and otherwise inaccessible territory in BSM theories.
As high temperature superconductor magnet applications become a reality due to increases in conductor performance, it is important to understand the behavior of normal zones in conductors and magnets ...in order to design safe magnet systems. Here we study the effects of localized heat pulses in Ag-alloy sheathed Bi
2Sr
2Ca
2Cu
3O
x
powder-in-tube conductors and Ni-alloy substrated YBa
2Cu
3O
x
coated conductor tapes cooled by N
2 gas. A heater was used to initiate a normal zone. The experimental setup to measure the energy required such that the normal zone propagates and the normal zone propagation velocity in the longitudinal direction is described. Results for both conductor architectures are presented.
The investigation of quenching in low temperature superconducting wires is of great relevance for a proper design of superconductive cables and magnets. This paper reports the experimental results of ...a vast measurement campaign of quench induced by laser pulses on NbTi and Nb3Sn wires in pool boiling helium I. A comparison of the quench behavior of two typical NbTi and Nb3Sn wires is shown from different standpoints. Different qualitative behaviors of the voltage traces recorded during quenches and recoveries on NbTi and Nb3Sn wires are reported and analyzed. It is shown that the Nb3Sn wire exhibits a quench or no-quench behavior, whereas quenches and recoveries are exhibited by the NbTi wire. The two wires are also compared by considering the behaviors of the two main parameters describing quench, i.e. quench energies and quench velocities, with respect to operating current, pulse duration, and magnetic field. It is shown that the Nb3Sn wire exhibits a 'kink' of the quench energy versus current curve that makes the quench energy of Nb3Sn lower than that of NbTi at some intermediate current levels. Both the qualitative differences of the voltage traces and the different behaviors of quench energies and velocities are interpreted through a coupled electromagnetic-thermal model, with special emphasis on the detailed description of heat exchange with liquid helium.
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