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Superconducting magnets of future fusion reactors are expected to rely on composite high-temperature superconductor (HTS) cable conductors. In presently used HTS cables, current sharing between components is limited due to poorly defined contact resistances between superconducting tapes or by design. The interplay between contact and termination resistances is the defining factor for power dissipation in these cables and ultimately defines their safe operational margins. However, the current distribution between components along the composite conductor and inside its terminations is a priori unknown, and presently, no means are available to actively tune current flow distribution in real-time to improve margins of quench protection. Also, the lack of ability to electrically probe individual components makes it impossible to identify conductor damage locations within the cable. In this work, we address both problems by introducing active current control of current distribution between components using cryogenically operated metal-oxide-semiconductor-field-effect transistors (MOSFETs). We demonstrate through simulation and experiments how real-time current controls can help to drastically reduce heat dissipation in a developing hot spot in a two-conductor model system and help identify critical current degradation of individual cable components. Prospects of other potential uses of MOSFET devices for improved voltage detection, AC loss-driven active quench protection, and remnant magnetization reduction in HTS magnets are also discussed.

The parabolic problem ut−Δu=λf(x)(1−u)2+P$$ {u}_t-\Delta u&#x0003D;\frac{\lambda f(x)}{{\left(1-u\right)}&#x0005E;2}&#x0002B;P $$ on a bounded domain Ω$$ \Omega $$ of Rn$$ {R}&#x0005E;n $$ with Dirichlet boundary condition models the microelectromechanical systems (MEMS) device with an external pressure term. In this paper, we classify the behavior of the solutions to this equation. We first show that under certain initial conditions, there exist critical constants P∗$$ {P}&#x0005E;{\ast } $$ and λP∗$$ {\lambda}_P&#x0005E;{\ast } $$ such that when 0≤P≤P∗,0<λ≤λP∗$$ 0\le P\le {P}&#x0005E;{\ast },0<\lambda \le {\lambda}_P&#x0005E;{\ast } $$, there exists a global solution, while for 0≤P≤P∗,λ>λP∗$$ 0\le P\le {P}&#x0005E;{\ast },\lambda >{\lambda}_P&#x0005E;{\ast } $$ or P>P∗$$ P>{P}&#x0005E;{\ast } $$, the solution quenches in finite time. The estimates of voltage λP∗$$ {\lambda}_P&#x0005E;{\ast } $$, quenching time T$$ T $$, and pressure term P∗$$ {P}&#x0005E;{\ast } $$ are investigated. The quenching set Σ$$ \varSigma $$ is proved to be a compact subset of Ω$$ \Omega $$ with an additional condition on f(x)$$ f(x) $$, provided Ω⊂Rn$$ \Omega \subset {R}&#x0005E;n $$ is a convex bounded set. In particular, if Ω$$ \Omega $$ is radially symmetric, then the origin is the only quenching point. Furthermore, we not only derive the two‐sided bound estimate for the quenching solution but also obtain its asymptotic behavior near the quenching time. [ABSTRACT FROM AUTHOR]

Alkali metals, including lithium, sodium, and potassium, are exceptionally reactive due to their pyrophoric water reactive behavior and are widely used in chemical research laboratories. They have also been the cause of numerous laboratory fires. Lithium metal even reacts with nitrogen gas to form highly reactive lithium nitride as a surface contaminant. Quenching of alkali metals and lithium nitride can follow the same protocol, but it is critical that the quenching be properly conducted to avoid fires. Improperly conducted quenches described herein resulted in significant fires with equipment damage but fortunately no personal injuries. In light of those events, a thorough discussion of quenching considerations, challenges, and protocols are followed by comprehensive and detailed guidance for quenching these reactive metals. [ABSTRACT FROM AUTHOR]

2′-(hexyloxy)-[1,1′-biphenyl]-2-yl 5-(dimethylamino)naphthalene-1-sulfonate (KC1) was synthesized by using biphenol and dansyl chloride as starting materials. The KC1 was characterized via single X-ray diffraction, FTIR, HRMS and 1H and 13C-NMR. The KC1 indicates triclinic as P1 in the space group type. From the KC1, the biphenolic backbone structure is twisted at an angle of 54.48° due to connecting the dansyl unit and hexyl moiety. Upon the addition of the Fe3+ ion to the KC1 solution, the fluorescence emission at 585 nm of KC1 was quenched due to complexation between KC1 and the Fe3+ ion. The complexation ratio of KC1 and Fe3+ was determined to be a 1:1 formation via Job's analysis. The Stern–Volmer constant (Ksv) calculated was 21,203 M−1 for the KC1 and the Fe3+ ion complex. [ABSTRACT FROM AUTHOR]

The Spherical Tokamak for Energy Production (STEP) requires high-field magnet designs and has therefore adopted the REBCO-based high-temperature superconductor (HTS) as its current carrier. The HTS enables the toroidal field (TF) coils to be remountable, which unlocks STEP's vertical maintenance approach; however, remountable joints, approximately 18 GJ of stored energy and limited space down the centre of a spherical tokamak, make the TF coils the most challenging. STEP has pursued a passive approach to TF coil quench protection in order to limit coil terminal voltage. Initial results suggest that a solution may rely on tuning internal coil resistance coupled with actively powered heaters. The pre-conceptual inter-coil structure demonstrates acceptable stresses and deflections under steady-state operating conditions and preliminary fault scenarios, and loads are distributed to limit the tensile force on the TF centre rod. Finally, the HTS must operate reliably in a high radiation environment and endure high neutron fluences, ensuring commercially relevant magnet lifetimes. Initial experiments indicate that instantaneous gamma irradiation of HTS has no negative impact on current carrying capacity. Experimental programmes are underway to cold irradiate HTS to fusion-relevant fluences and to develop a method of assuring tape irradiation tolerance using oxygen ions as an analogue for neutrons. This article is part of the theme issue 'Delivering Fusion Energy – The Spherical Tokamak for Energy Production (STEP)'. [ABSTRACT FROM AUTHOR]

Biochemical analysis is of great significance in many fields, such as disease diagnosis, environmental pollution source identification, food safety, etc. Immunoassay based on the reaction of antigen and antibody has the characteristics of high specificity and diversity. Compared with other analytical methods such as liquid chromatography, which requires a large and expensive instrument, immunodetection has the advantages of simplicity and good selectivity and is thus widely used in sample testing. Quenchbody (Q-body) is a novel fluorescent immunosensor based on antigen-antibody reaction. It is constructed by labeling antibody fragment with fluorescent dye. Tryptophan in antibody leads to electron transfer and quenching of fluorescent, when it specifically binds with antigen, its fluorescence intensity recovers and presents concentration dependence. Therefore, the antigen concentration can be detected by detecting the change of fluorescence intensity of the Q-body. Q-body immunoassay is widely used in the rapid detection of environmental pollutants and disease markers due to its simple operation and high sensitivity, which is of great significance for environmental detection and disease diagnosis. In this paper, the principle, construction method, detection technology development and domestic and foreign research progress of Q-body are comprehensively discussed, and the future application of this technology is prospected [ABSTRACT FROM AUTHOR]

High-temperature superconducting (HTS) rare-earth Ba2Cu3O7−x (REBCO) coated conductors (CCs) have significant potential in high-current and high-field applications. However, owing to the weak interface strength of the laminated composite REBCO CCs, the damage induced by the thermal mismatch stress under a combination of epoxy impregnation, cooling, and quenching can cause premature degradation of the critical current. In this study, a three-dimensional (3D) electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model (CZM) is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench. The temperature variation, critical current degradation of the REBCO CC, and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature. The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result. The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC. The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC. Finally, the effects of the coefficient of thermal expansion (CTE) of the epoxy resin, thickness of the substrate, and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed. These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications. [ABSTRACT FROM AUTHOR]

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The study addresses the design and operational features of an active condensation (AC) system aimed at improving the energy efficiency of a 3rd generation district heating (DH) plant. Several similar biomass-utilizing plants have recently been built in the Republic of Serbia. The plant is equipped with biomass-fired boilers totaling 2 MW capacity, utilizing varying qualities of wet wood chips. The goals are: (i) to determine optimal constant and variable quench temperatures; (ii) to calculate the electricity consumption of ancillary devices and assess their impact on AC system performance; (iii) to evaluate the effect of biomass moisture variations on system size and performance; (iv) to assess the economic viability of integrating the AC system; and (v) to establish selection and design criteria for the heat pump (HP). For a given commercial HP, an optimal quench temperature exists, dependent on the minimal temperature lift required by the HP. This temperature can be calculated simply by subtracting the minimal HP lift from the lowest possible temperature that the HP can supply to a DH system at the average outdoor temperature. Consequently, an optimal variable quench temperature exists that should be adjusted to enable the HP to operate with its minimal temperature lift.

In order to optimize the measurement conditions of 55Fe by liquid scintillation counting, the effect of three kinds of commercial scintillation cocktail and two efficiency correction methods on LSC measurements of 55Fe was tested. Configuration of 55Fe samples with the same matrix as after radiochemical treatment for measurement, Ultima Gold AB has the highest sample loading among the three kinds of scintillation cocktail; the counting efficiency of Ultima Gold LLT is the highest and the MDA is the lowest under different miscibility ratios, and the maximum detection efficiency of Ultima Gold LLT is 49.1% when the miscibility ratio is 1∶4, while the MDA is 0.12 Bq. If the sample uses scintillation cocktail different from the quenched standard source, it will have an impact on the accuracy of the results, with an absolute value of maximum average relative deviation is 3.55% between the measured and expected values under experimental conditions. Comparing the two quenching calibration methods of tSIE and TDCR, the TDCR method can eliminate the influence caused by the simultaneous presence of color and chemical quenching on the 55Fe LSC measurement results, and is a more accurate method for measuring 55Fe. The relative deviations between the measured and expected values obtained from the color and chemical quenching calibration curves are -0.35% to 0.40% and -0.91% to -0.16%, respectively, as verified by the spiked samples.

2′-(hexyloxy)-[1,1′-biphenyl]-2-yl 5-(dimethylamino)naphthalene-1-sulfonate (KC1) was synthesized by using biphenol and dansyl chloride as starting materials. The KC1 was characterized via single X-ray diffraction, FTIR, HRMS and 1H and 13C-NMR. The KC1 indicates triclinic as P1 in the space group type. From the KC1, the biphenolic backbone structure is twisted at an angle of 54.48° due to connecting the dansyl unit and hexyl moiety. Upon the addition of the Fe3+ ion to the KC1 solution, the fluorescence emission at 585 nm of KC1 was quenched due to complexation between KC1 and the Fe3+ ion. The complexation ratio of KC1 and Fe3+ was determined to be a 1:1 formation via Job’s analysis. The Stern–Volmer constant (Ksv) calculated was 21,203 M−1 for the KC1 and the Fe3+ ion complex.

As a combustor that can reduce pollutant emissions, the trapped-vortex combustor can not only reduce the length of the combustor because of its radial classification technology, but also its design concept is inseparable from RQL (Rich burn, Quench, and Lean burn). In this paper, the effects of cavity equivalence ratio and fuel injection cone angle on combustion performance and NOx emission were studied by numerical simulation. It is found that the trapped-vortex combustor achieves RQL combustion mode. The increase of the cavity equivalence ratio results in the non-uniform fuel distribution. However, the fuel injection cone angle in the primary region has little effect on the fuel distribution. With the increase of the cavity equivalence ratio, the combustion efficiency and NOx emission first decrease and then increase, and outlet temperature distribution factor is positively correlated with the cavity equivalence ratio. The difference is that the outlet temperature distribution factor and combustion efficiency show almost the same law with the increase of injection cone angle in the primary region, and the NOx emission decreases, but the reduction is not significant.

As the simplest and most fundamental model describing the interaction between light and matter, a breakdown in the rotating wave approximation of the Rabi model leads to phase transition versus coupling strength when the frequency of the qubit greatly surpasses that of the oscillator. In addition to the phase transition revealed in the ground state, we show that the dynamics of physical quantities can reflect such a phase transition for this model. In addition to the excitation of the bosonic field in the ground state, we show that the witness of inseparability (entanglement), mutual information, quantum Fisher information, and the variance of cavity quadrature can be employed to detect the phase transition in quench. We also reveal the negative impact of temperature on checking the phase transition by quench. This model can be implemented using trapped ions, superconducting artificial atoms coupled bosonic modes, and quantum simulations. By reflecting the phase transition in a fundamental quantum optics model without imposing the thermodynamic limit, this work offers an idea to explore phase transitions by nonequilibrium process for open quantums. [ABSTRACT FROM AUTHOR]

For the study, to effectively promote the activity of waste brick powders for recycling, they were being treated by microwave radiation, calcination, and chemical-activation. Specimens of neat paste were prepared with a 7 ∶3 mass ratio of cement and waste brick powder and 3 d, 7 d, 14 d and 28 d compressive strength of the specimens was tested. Their crystal phase composition and micro-structure were observed by XRD and SEM. The results showed that the amorphization of Al2O3was promoted in the waste brick powder by microwave radiation and the compressive strength of the neat paste of cement and waste brick powder was increased in 3-28 d and increased with the increase of the time of microwave radiation. The increase of the activity of waste brick powder was not influenced significantly by quenching after microwave radiation. At the temperature between 600 ℃ and 800 ℃, the activity of waste brick powder was on the increase with the increase of the temperature of calcination. The activity of waste brick powder quenched immediately after calcination at high temperature was better than that activated by microwave radiation. The activation by HMTA and sodium aluminate led to the development of a large amount of AFm in the neat paste of cement-waste brick powder at the age of 28 d while the C-A-S-H and AFt developed during the activation by polyaluminium chloride (PAC) had smaller size and were stable, and the micro-structure of the hardened paste was more dense. [ABSTRACT FROM AUTHOR]

ReBCO superconducting cables have the potential to enable compact thermonuclear fusion reactors that operate at magnetic fields exceeding 20 T and allow operation at temperatures far exceeding the boiling point of liquid helium, potentially allowing for demountable magnets. Normal zone detection remains a challenge, and while novel quench detection techniques are an active area of research, few are non-invasive, provide real-time quench detection, and have been demonstrated with current ramp rates relevant for fusion reactors. To address this problem, a CORC® cable termination is developed with integrated Hall sensors to monitor current redistribution as a proxy for quench detection. The methodology exploits the current sharing and layered topology in CORC® cables, and allows quench detection using a localized sensor instead of co-wound voltage wires or optical fibers. Experiments are presented where current redistribution is measured from induced quenches, and in a 0.2 meter CORC® sample it is found that the Hall sensors detect normal zone transitions with a similar magnitude and temporal resolution as voltage measurements. To emulate the conditions of dynamic poloidal and central solenoidal fields, experiments are repeated with ramp rates up to 10 kA s-1 that demonstrate the potential to detect normal zone development over a range of experimental parameters.

In this paper, we report an occurrence of ultramafic pseudotachylytes, providing fault-rock evidence of paleo-earthquakes, from the Luobusha ophiolite complex in the Yarlung Zangbo suture zone. The pseudotachylytes form hairline-thin aphanitic veinlets and vein networks bounded by micro-damage zones cutting through the host harzburgite, forming flow banding in some places. The pseudotachylyte veins are dominated by close-knit ultrafine-grained minerals consisting of olivine, orthopyroxene, serpentine, spinel, and magnetite, cemented by an extremely fine matrix. As the primary component of the pseudotachylyte veins, olivine occurs as microphenocryst showing zoning from core to rim and as irregularly shaped microlite immersed in the interstitial material. Zoned crystals of olivine developed with Mg-rich cores and more Fe-rich rims. Microlite diagnosis of crystallization in a quenched melt includes dendritic, skeletal, and poikilitic olivine crystals, which are typical of ultramafic pseudotachylyte. The olivine microlites contain higher amounts of Ca, Al, and Cr but a lower Ni content compared with the host harzburgite olivine. Irregularly shaped chrome-spinel crystals are chemically zoned as well, indicating an Fe-rich rim overgrowth. Ni sulfide droplets interspersing among the matrix imply melt occurrence. The presence of a micro-fibrous and micro-vesicular interstitial matrix also indicates a melting-related origin. Ultracataclastite veins associated with pseudotachylyte transecting serpentine are observed, which convey that heat was generated during rapid comminution and injection. The characteristic petrography, microtextures, and chemical inhomogeneities meet the criteria of ultramafic pseudotachylyte and reveal a mixed genesis via a combination of crushing and melting. The development of extremely tiny globular prograde serpentine inclusions (∼100 nm) in the olivine microlites is ascribed to the dehydration reaction of serpentine to olivine within the pseudotachylyte. The Luobusha metamorphogenic peridotite was subjected to serpentinization after having emplaced in the crust and subsequently to high-pressure metamorphism. The pseudotachylytes were generated in the crust after the high-pressure metamorphism and did not descend to a greater depth. Flash ultra-comminution associated with frictional heating may release fluids via localized heat-driven prograde reactions in the crust.

For the high luminosity upgrade of the CERN large hadron collider, lower β∗ quadrupole magnets based on advanced Nb3Sn conductors will be installed on each side of the ATLAS and compact muon solenoid (CMS) experiment insertion zones. As part of the technological developments needed to achieve the required field gradient of 132.6 T/m within a 150-mm aperture, short length model magnets, named MQXFS, are tested both at the CERN SM18 and Fermilab test facilities. The model magnets rely on two types of Nb3Sn conductors (restack rod process (RRP) and powder-in-tube (PIT)) and on an innovative bladders and keys design to provide mechanical support against the Lorentz forces. In 2016 and 2017, the powering tests of the first two models MQXFS3 (RRP) and MQXFS5 (PIT) proved that nominal performance (16.5 kA) could be reached with excellent memory of the quench current after thermal cycle. However both magnets showed a slow training behavior with clear observations of voltage disturbances before the quench. Besides, only MQXFS5 could reach ultimate current (17.9 kA) whereas erratic behavior was observed on MQXFS3 due to conductor local degradation at the head of one of the coils. In 2018, this limiting coil was changed and the applied azimuthal prestress increased. While ultimate current could then be reached, no stable current could be maintained due to identified defect on the outer layer of the new coil. Finally the outcome of the test of the new model MQXFS4, featuring the final RRP conductors that will be used for the series production and variation on the inner layer quench heater designs are here reported in details.

High field superconducting magnets for particle accelerators often exhibit premature quenches. Once a normal zone is generated within the conductor, the quench may propagate causing temperature and resistive voltage rise along the coil. The resulting thermal gradients can potentially cause new peak stresses that might exceed the tolerable limits, degrading the conductor. The computation of the strain state in the coils during quench then becomes of paramount importance for magnet design, and requires a complete three-dimensional (3-D) analysis of quench phenomena. The objective of this paper is to present the first multiphysics modeling activities towards a new full 3-D methodology for the analysis of magnet mechanics during quench. As a first step, a 3-D thermal-electric finite element model of a Nb3Sn superconducting coil is developed and explained here. The model uses direct coupled-field elements to solve the system of thermal and electrical equations. A solving algorithm has also been implemented in order to investigate the physics behind quench transients. The output from this model, built in ANSYS APDL, can be easily coupled in a later stage to a mechanical model in order to estimate the strain state in the coil windings. A very good agreement has been observed between the numerical results and experimental tests performed in individual superconducting cables and real superconducting magnets.

For the high luminosity upgrade of the CERN large hadron collider, lower β∗ quadrupole magnets based on advanced Nb3Sn conductors will be installed on each side of the ATLAS and compact muon solenoid (CMS) experiment insertion zones. As part of the technological developments needed to achieve the required field gradient of 132.6 T/m within a 150-mm aperture, short length model magnets, named MQXFS, are tested both at the CERN SM18 and Fermilab test facilities. The model magnets rely on two types of Nb3Sn conductors (restack rod process (RRP) and powder-in-tube (PIT)) and on an innovative bladders and keys design to provide mechanical support against the Lorentz forces. In 2016 and 2017, the powering tests of the first two models MQXFS3 (RRP) and MQXFS5 (PIT) proved that nominal performance (16.5 kA) could be reached with excellent memory of the quench current after thermal cycle. However both magnets showed a slow training behavior with clear observations of voltage disturbances before the quench. Besides, only MQXFS5 could reach ultimate current (17.9 kA) whereas erratic behavior was observed on MQXFS3 due to conductor local degradation at the head of one of the coils. In 2018, this limiting coil was changed and the applied azimuthal prestress increased. While ultimate current could then be reached, no stable current could be maintained due to identified defect on the outer layer of the new coil. Finally the outcome of the test of the new model MQXFS4, featuring the final RRP conductors that will be used for the series production and variation on the inner layer quench heater designs are here reported in details.

Palladium hydrides (PdHx) have important applications in hydrogen storage, catalysis, and superconductivity. Because of the unique electron subshell structure of Pd, quenching PdHx materials with more than 0.706 hydrogen stoichiometry remains challenging. Here, the 1:1 stoichiometric PdH (Fm3¯m)$Fm\bar{3}m)$ is successfully synthesized using Pd nano icosahedrons as a starting material via high‐pressure cold‐forging at 0.2 GPa. The synthetic initial pressure is reduced by at least one order of magnitude relative to the bulk Pd precursors. Furthermore, PdH is quenched at ambient conditions after being laser heated ≈2000 K under ≈30 GPa. Corresponding ab initio calculations demonstrate that the high potential barrier of the facets (111) restricts hydrogen atoms' diffusion, preventing hydrogen atoms from combining to generate H2. This study paves the way for the high‐pressure synthesis of metal hydrides with promising potential applications. [ABSTRACT FROM AUTHOR]

Quantum interference effects appearing in mesoscopic heterostructures have been extensively studied in static conditions over the last decades. It is interesting to examine the dynamics of these phenomena and get insight into the process of the formation of interference patterns. In this work, we analyze the time required for the formation of Fano-like resonances in a double quantum dot system. We examined the time evolution of conductance upon establishing an abrupt connection between quantum dots. Asymmetric Fano lines are characterized by the close coexistence of resonant enhancement and resonant suppression. Therefore, we pay particular attention to voltages, which in the static case, correspond to both these features. Our research shows that the analyzed resonances are characterized by two time scales: (i) the first one related to charge oscillations between subsystems and mostly governed by the interdot coupling constant and the relative position of energy levels of quantum dots, and (ii) the second one associated to the electron scattering on a continuum of states and responsible for the relaxation. We also show that the time required for achieving a static solution is different for voltages corresponding to local minima and local maxima. [ABSTRACT FROM AUTHOR]

Due to epitaxial strain, BiFeO 3 (BFO) thin films exhibit a morphotropic phase boundary with coexisting rhombohedral-like (R-like) and tetragonal-like (T-like) phases. The T-like phase, distinguished by its large c/a ratio and giant polarization, has garnered extensive interest. In this work, by quenching an epitaxial mixed-phase BFO thin film grown on a LaAlO 3 substrate, a pronounced transition from the R-like to the T-like phase is observed. This transition is concomitant with improved phase structure stability under the force field induced by an atomic force microscope tip. PeakForce Quantitative NanoMechanics mapping reveals that the T-like phase exhibits a higher Young's modulus than the R-like phase, signifying an overall enhancement in the mechanical hardness of the BFO film. This work introduces a simple but powerful approach to manipulating the fraction of the T-like phase in the mixed-phase BFO films, presenting prospects for enhancing their performance and expanding their application range in advanced techniques. [Display omitted] [ABSTRACT FROM AUTHOR]

The high luminosity upgrade project U.S. LARP/HiLumi has successfully tested the first 1.5 m prototype quadrupole MQXFS1 at Fermilab’ Magnet test facility. Several thermal cycles and test programs were performed, with different preload configurations. To localize and characterize quenches, a quench antenna and voltage taps are used. The quench antenna was placed inside a warm bore of an anticryostat centered in the magnet. We varied the length between quench antenna segments from 2.54 to 15.24 cm, and shifted the location of the antenna to localize the quench origin along the various wedge and spacers transitions in the lead end of the magnet. We present results on the identified quench locations for the second and third thermal cycle in this paper.

The quenching heat treatment is, probably, the most common way to adjust the mechanical properties of steels, however, it is also responsible for a high percentage of rejections of manufactured parts, due to the large number of process variables involved. The defects that most contribute to scrap in hardened parts are cracking and distortion outside dimensional tolerances. The C-Ring type specimens have been used as a method of evaluating both the quenching conditions and the hardenability of steels in industrial and laboratory environments, in addition to this, the availability of specialized tools in finite elements simulation allow the design of models that replicate the real behavior of industrial applications that allow designing suitable quenching treatments capable of foreseeing the optimal conditions avoiding known defects. [ABSTRACT FROM AUTHOR]

Fluctuations in the critical current along the length of high-temperature superconducting (HTS) tapes manufactured in the form of coated conductors is a common manufacturing phenomenon. These fluctuations originate in the generation of weak points through the length of HTS tapes that may cause quenching later. By means of the propagation of quenches in HTS tapes, the reliability, stability, and the performance of the device and the system that contain HTS tapes could be seriously degraded. In this study, an artificial intelligence technique based on artificial neural networks (ANN) was proposed to estimate the probability of quenches in HTS tapes caused by weak points. For this purpose, six different HTS tapes were considered with different widths, total thicknesses, and thicknesses of sub-layers. Then, for each one of these tapes, different operating conditions were considered, where the operating temperature changed from 40 K to 80 K, in 1 K steps. Under each operating temperature, different operating currents were considered from 50% to 100% of tape critical current. All of these resulted in more than 5000 different data points. Then, for each of these data points, analytical modelling was performed to provide initial inputs and outputs for the ANN model. It should be noted that the performed simulations were conducted based on an analytical method that was experimentally validated in the literature. After that, a sensitivity analysis was conducted to select the hyperparameters and structure of the ANN-based model. The last step was to take advantage of the trained model, as a function in the MATLAB software package to estimate the probability of quenches in different case studies. The significant feature of the proposed model is the capability for estimating the probability of quenches under different operating temperatures and currents for different types of HTS tapes. [ABSTRACT FROM AUTHOR]

Epoxy resins are a material that is widely used in high-field superconducting magnet impregnation. As the magnets run under low temperatures and high fields with high current density, it is necessary to investigate the mechanical properties of the epoxy resins and the performances of the impregnated superconducting conductors. Here, the tensile and compression properties of four epoxy/AlN composites with different AlN ratios at 300 K have been studied, then the quench behaviors of 4-mm-wide REBCO-coated conductors impregnated with the epoxy/AlN composites at 77 K have been investigated. The strength and rigidity of the epoxy/AlN composites have been tested, and the minimum quench energy (MQE) and normal zone propagation velocity (NZPV) of REBCO conductors impregnated with epoxy/AlN composites have been studied through a series of quench experiments. The results indicate that with a higher AlN ratio, the mechanical strength of the epoxy/AlN composites will be impaired and the rigidity will be improved, which is caused by the agglomeration of AlN particles. It shows that compared with pure epoxy, the composites with an AlN ratio of 5 to 10 % can provide less strength decrease and enhance the quench performances of the impregnated REBCO-coated conductors: 9.3 % higher MQE or 10.5 % faster NZPV. The better thermal performance of the composites can be attributed to the high thermal conductivity of the AlN particles. [ABSTRACT FROM AUTHOR]

As the simplest and most fundamental model describing the interaction between light and matter, a breakdown in the rotating wave approximation of the Rabi model leads to phase transition versus coupling strength when the frequency of the qubit greatly surpasses that of the oscillator. In addition to the phase transition revealed in the ground state, we show that the dynamics of physical quantities can reflect such a phase transition for this model. In addition to the excitation of the bosonic field in the ground state, we show that the witness of inseparability (entanglement), mutual information, quantum Fisher information, and the variance of cavity quadrature can be employed to detect the phase transition in quench. We also reveal the negative impact of temperature on checking the phase transition by quench. This model can be implemented using trapped ions, superconducting artificial atoms coupled bosonic modes, and quantum simulations. By reflecting the phase transition in a fundamental quantum optics model without imposing the thermodynamic limit, this work offers an idea to explore phase transitions by nonequilibrium process for open quantums.

Gas explosion is a common serious accident in underground coal mines and industrial production processes. Porous media, due to its special cellular structure, has a significant effect on stopping the propagation of pressure and flame, which can effectively reduce the explosion hazard. In this study, the explosion suppression effect of Fe-Ni and Cu foams with different pore sizes (20 and 40 holes pores per inch (ppi)) was experimentally investigated and comparatively analyzed at opening blockage ratios (OBR) equal to 0.36, 0.64 and 0.84, respectively. The results demonstrate that Fe-Ni foam with 20ppi quenches the flame only under the OBR of 0.84, which indicates that the larger the OBR is, the better the explosion suppression effect is. However, under the OBR of 0.64, the porous media achieve an enhanced quenching efficiency and the shortest quenching time. In addition, when the vent area is relatively large, the obstacle effect of porous media is stronger than its pressure absorption capacity, thus leading to an increased pressure in the explosion area. The lowest peak overpressure attenuation rate, − 25.9%, is observed for 40ppi Fe-Ni foam under the OBR of 0.36. In general, the OBR is positively correlated with the depressurization capacity. Among all the cases used in this study, the 20ppi Cu foam boasts the highest upstream and downstream peak overpressure attenuation rates under three OBRs, 0.86%, and 6.33%, respectively. [ABSTRACT FROM AUTHOR]

This paper investigates the evolution of the microstructure of 17CrNiMo6 steel produced by carburizing and quenching through computer-aided engineering (CAE) and experimental study. The chemical composition, microstructure, and properties vary from surface to the core during the carburizing and quenching, which makes the CAE simulation of temperature field and microstructure evolution more complex. The performance–temperature and field performance–microstructure iterations using different simulation methods are applied. The results showed that the CAE forecast microstructure evolution is consistent with the experiment. The error between the predicted and experimental values from the surface to 2000 μm is 5%–9%, and the predicted results are consistent with the experiment at the depth of 2000 μm. [ABSTRACT FROM AUTHOR]

High-field MQXF-series quadrupoles are presently under development by LARP and CERN for the upcoming LHC luminosity upgrade. Quench training and protection studies on MQXF prototypes require a capability to accurately localize quenches and measure their propagation velocity in the magnet coils. The voltage tap technique commonly used for such purposes is not a convenient option for the 4.2-m-long MQXF-A prototype, nor can it be implemented in the production model. We have developed and tested a modular inductive magnetic antenna for quench localization. The base element of our quench antenna is a round-shaped printed circuit board containing two orthogonal pairs of flat coils integrated with low-noise preamplifiers. The elements are aligned axially and spaced equidistantly in 8-element sections using a supporting rod structure. The sections are installed in the warm bore of the magnet, and can be stacked together to adapt for the magnet length. We discuss the design, operational characteristics and preliminary qualification of the antenna. Axial quench localization capability with an accuracy of better than 2 cm has been validated during training test campaign of the MQXF-S1 quadrupole.

As part of the European Strategy for Particle Physics there is an ongoing development towards a Future Circular Collider (FCC-ee) where electron-positron collisions could be used to study the entire electro-weak sector in a low background environment. Particle detectors are used to study these collisions and a strong magnetic field is required to measure the particles’ momenta. Currently, two detector concepts are being studied: the Innovative Detector for Electron-positron Accelerators (IDEA) and the CLIC-Like Detector (CLD). Both these detectors include a superconducting solenoid magnet with a central field of $2 \,\mathrm{T}$ of which the designs are presented here. The IDEA magnet has an stored magnetic energy density of 14 kJ/kg and in CLD this is 12 kJ/kg. Taking into account their respective free-bore diameters of $4.2 \,\mathrm{m}$ for IDEA and $7.2 \,\mathrm{m}$ for CLD this results in very challenging designs for which the mechanical and quench studies are presented. Their results are promising, but extensive R&D on these magnets would be needed in the future to reach the goals set out in the Conceptual Design Report (CDR). [ABSTRACT FROM AUTHOR]

Development of REBCO cables that carry high electrical current in high magnetic field is crucial for future large-scale magnet applications. This experimental work presents the critical current measurements of two different REBCO cables by a test facility at the National High Magnetic Field Laboratory (NHMFL). The simple-stacked cable is made by the NHMFL by stacking 21 REBCO tapes without soldering. The Conductor on Round Core (CORC) cable provided by Advanced Conductor Technologies has 21 layers of REBCO tapes with 2 tapes/layer. The test facility consists of a 12 T split solenoid magnet with 15 cm bore providing transverse field to the samples, a superconducting transformer (SCT) as a current source providing up to 45 kA current. Special attention was paid to fabrication of solder joints between REBCO cables and the SCT output. The voltage-current traces were measured as a function of magnetic field at 4.2 K, from which the critical currents were determined. The details of this measurement are discussed. [ABSTRACT FROM AUTHOR]

The no-insulation (NI) winding approach can remarkably improve the thermal stability of high-temperature superconducting coil. However, mechanical issues have gradually become a key factor to block the development of NI magnets in recent years. This paper mainly analyzes the effect of the overband on the mechanical behaviors of an NI coil during a quench. A numerical model including a quench model combined with a three-dimensional homogeneous mechanical model is employed to study the change of stress in the coil without and with the overband during a local quench. The results show that the overband has an obvious effect on the stress distribution as the heater is located at the outer turn of the coil. Meanwhile, the values of stress in the coil are also affected by the overband. Moreover, the effects of the thickness of the overband and the location of the heater on the mechanical behaviors of the coil are also discussed. It is worth noting that the overband can remarkably reduce the hoop and axial tensile stresses of the coil during a quench [ABSTRACT FROM AUTHOR]

The mixing morphology control plays a crucial role in photovoltaic power generation, yet this specific effect on device performances remains elusive. Here, we employed computational approaches to delineate the photovoltaic properties of layered heterojunction polymer solar cells with tunable mixing morphologies. One-step quench and two-step quench strategies were proposed to adjust the mixing morphology by thermodynamic and kinetic effects. The computation for the one-step quench revealed that modulating interfacial widths and interfacial roughness could significantly promote the photovoltaic performance of layered heterojunction polymer solar cells. The two-step quench can provide a buffer at a lower temperature before the kinetic quenching, leading to the formation of small-length-scale islands connected to the interface and a further increase in photovoltaic performance. Our discoveries are supported by recent experimental evidence and are anticipated to guide the design of photovoltaic materials with optimal performance. [ABSTRACT FROM AUTHOR]

Novel zinc carboxylates metal–organic frameworks (Zn-MOFs) with different sizes and shapes constructed by Zn(II) ions, succinate and isonicotinate were synthesized by a polymer-assisted method. The samples were characterized by scanning electron microscope, powder X-ray diffraction and fluorescence spectroscopy. Results indicated that the size and shape of the Zn-MOFs could be adjusted by changing the quantity of polyvinyl alcohol (PVA). Fluorescence sensing of 2-nitrotoluene, 4-nitrotoluene and 2,4-dinitrotoluene was also studied and the results revealed that the as-prepared Zn-MOFs with a sheet-like shape were highly sensitive to nitro-compounds and promising to be developed as a novel luminescent sensor for detection in nitroaromatic explosives. [ABSTRACT FROM AUTHOR]

For 30 years, training and unpredictable degradation in accelerator type high-field Nb3Sn magnets have seriously hampered Nb3Sn application. Training and deterioration have to be solved or at least better controlled. The global picture shows that most of the R&D and short model magnets start to train at some 40%â€"70% of the critical current and then creep up to almost the critical current within some 10â€"50 training steps. A typical class of failures leading to quenches is largely characterized by cracking and debonding at the interfaces between cable and glass-resin insulation, as well as between insulation and coil former. The study of training by means of testing demonstrator coils is rather expensive and time consuming. However, advances in magnet design and fabrication can also be assessed and benchmarked using BOX, the bonding experiment presented here, that produces maximum uniaxial Lorentz forces at some 7.5 T in a controlled experiment performed in 11 T solenoid facility at the University of Twente. BOX samples use only one meter of Nb3Sn cable inserted in a three-wave meandering slot in a flat metallic sample holder, reproducing magnet-relevant interactions between cable, insulation, impregnated materials and coil former. The meander shape exposes seven straight cable sections to a transverse magnetic field, thereby generating a representative level of shear stress at the interfaces. In this way, characteristic training curves of magnets can be mimicked and solutions studied. We aim to demonstrate with various samples failure mechanisms of high-field Nb3Sn magnets without the need to manufacture complete magnets. BOX may thus be expected to allow for quick and affordable testing of novel insulations, impregnation materials, coatings and interfaces for Nb3Sn magnets achieved by investigating various resins, fillers and more. [ABSTRACT FROM AUTHOR]

For practical application, stability investigation of high temperature superconductor (HTS) is of great importance. An insert set-up has been developed at the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP). Measurements are performed as a function of transport current and magnetic field for several operating temperatures between 30 and 50 K. This work focuses on the design of insert set-up and the estimation of normal zone propagation velocity (Vnzp) and minimum quench energy (MQE). The experimentally obtained temperature dependence of Vnzp is compared with a simplified adiabatic model. [ABSTRACT FROM AUTHOR]

An actively shielded 1.5 T superconducting MRI magnet is designed for a whole-body clinical scanner. During a quench, its fast-decaying field induces a strong eddy current in all the conductive parts of the cryostat. The eddy current together with the decaying magnetic field generates Lorentz force, which generates stress and deformation in the bobbin structure, thermal shield, and other conductive parts of the cryostat. In this article, we report the analysis of the eddy current distribution induced in the bobbin structure and thermal shield made of various alloys of the MRI magnet system using a finite element analysis program. The net forces on each part of the bobbin structure and the thermal shield and the associated stress distribution, the deformation are analyzed in detail using OPERA-3D software. The eddy-current-induced effects on a few metallic alloys are compared for generating design inputs for the bobbin structure and the thermal shield of the MRI magnet system. We also report the transient behavior of the eddy current in correlation with the decaying current during a quench. [ABSTRACT FROM AUTHOR]

Real-time monitoring of heat loads in cryogenic systems is critical for many applications, particularly high field magnets. We demonstrated that by monitoring changes in the capacitance of local probes consisting of thin metal strips with a porous glass fiber dielectric, boiling helium from as little as 0.1 J of deposited heat can be located by an analysis of the response speed and amplitude in nearby probes. We further implemented stray-capacitance monitoring of a magnet's metal support structures, a more global probe of the magnet volumes, in three high temperature superconducting Bi-2212 magnet types. Global structural stray-capacitance monitoring was evaluated for a single racetrack coil, a common coil dipole, and a canted cosine theta winding, showing a quench response comparable to voltage signals without inductive effects. The response of the local and global probes was compared in the single racetrack coil with well-known quench properties. Monitoring the cool-down of the common coil dipole demonstrated the added benefit of the global stray-capacitance as a liquid level monitor. This simple method of monitoring the capacitance has proven to be a versatile and robust technique for monitoring and locating heat. [ABSTRACT FROM AUTHOR]