Aluminum Loop Research Articles

Noninvasive Readout of the Kinetic Inductance of Superconducting Nanostructures.

The energy landscape of multiply connected superconducting structures is ruled by fluxoid quantization due to the implied single-valuedness of the complex wave function. The transitions and interaction between these energy states, each defined by a specific phase winding number, are governed by classical and/or quantum phase slips. Understanding these events requires the ability to probe, noninvasively, the state of the ring. Here, we employ a niobium resonator to examine the superconducting properties of an aluminum loop. By applying a magnetic field, adjusting temperature, and altering the loop's dimensions via focused ion beam milling, we correlate resonance frequency shifts with changes in the loop's kinetic inductance. This parameter is an indicator of the superconducting condensate's state, facilitating the detection of phase slips in nanodevices and providing insights into their dynamics. Our method presents a proof-of-principle spectroscopic technique with promising potential for investigating Cooper pair density in inductively coupled superconducting nanostructures.

Cooling of Electronic Components by an Aluminum Loop Thermosyphon Containing Two Evaporators and One Condenser

Cooling of Electronic Components by an Aluminum Loop Thermosyphon Containing Two Evaporators and One Condenser

Circularity assessment of the effects of customer preferences towards sustainable development on producers for aluminum-based products in Norway

A closed aluminum loop can potentially reduce CO2 emissions considerably by using more post-consumer scrap (PCS). Unfortunately, there is a wide gap between the potential uses of recycling aluminum and the real introduction of it in structural aluminum-based products. In the case of Norway, the main criterion for customers is the quality of the product, challenging the usage of a high percentage of recycled aluminum in the casting mix. This paper aims to evaluate the influence of factors such as sustainable awareness and quality requirements from the customer perspective on the casting mix demand and the material flow that such demand will have on the manufacturing system. System Dynamics is used to model aluminum production and recycling in Norway and to understand the dynamics among the actors and material flow with changes in demand. A Causal Loop Diagram was built, mapping the decision-making process that generates the material flow in the automotive recycle aluminum value chain.

Operating in a deep underground facility improves the locking of gradiometric fluxonium qubits at the sweet spots

We demonstrate flux-bias locking and operation of a gradiometric fluxonium artificial atom using two symmetric granular aluminum (grAl) loops to implement the superinductor. The gradiometric fluxonium shows two orders of magnitude suppression of sensitivity to homogeneous magnetic fields, which can be an asset for hybrid quantum systems requiring strong magnetic field biasing. By cooling down the device in an external magnetic field while crossing the metal-to-superconductor transition, the gradiometric fluxonium can be locked either at 0 or Φ0/2 effective flux bias, corresponding to an even or odd number of trapped fluxons, respectively. At mK temperatures, the fluxon parity prepared during initialization survives to magnetic field bias exceeding 100 Φ0. However, even for states biased in the vicinity of 1 Φ0, we observe unexpectedly short fluxon lifetimes of a few hours, which cannot be explained by thermal or quantum phase slips. When operating in a deep-underground cryostat of the Gran Sasso laboratory, the fluxon lifetimes increase to days, indicating that ionizing events activate phase slips in the grAl superinductor.

Implementation of the nudged elastic band method in a dislocation dynamics formalism: Application to dislocation nucleation

We propose a framework to study thermally-activated processes in dislocation glide. This approach is based on an implementation of the nudged elastic band method in a nodal mesoscale dislocation dynamics formalism. Special care is paid to develop a variational formulation to ensure convergence to well-defined minimum energy paths. We also propose a methodology to rigorously parametrize the model on atomistic data, including elastic, core and stacking fault contributions. To assess the validity of the model, we investigate the homogeneous nucleation of partial dislocation loops in aluminum, recovering the activation energies and loop shapes obtained with atomistic calculations and extending these calculations to lower applied stresses. The present method is also applied to heterogeneous nucleation on spherical inclusions.

Mechanical design of a novel MEMS resonant sensor for monitoring in-plane magnetic fields

We present the mechanical design of a novel MEMS-based magnetic field sensor with optical sensing for monitoring in-plane magnetic fields. It has a diamond-shaped resonator composed by four polysilicon beams (198 × 12 × 2.25 µm), an aluminum loop (957 × 8 × 0.7 µm) and two mirrors (31 × 32 × 0.7 µm), which are designed considering the Sandia Ultra-planar Multi-level MEMS Technology process. The sensor exploits Lorentz force to detect different components of in-plane magnetic fields, which are related with the mirrors displacements. Analytical models are developed to predict the damping, resonant frequency, and mirrors displacements caused by temperature shifts. In addition, Castigliano's second theorem is used to obtain an analytical model of the mirrors displacements at resonance as a function of in-plane magnetic fields with inclination angles from 0 to 360° and electrical currents. The results of the analytical models agree well with those determined by finite element method models. The sensor operates at resonant frequency of 33.6 kHz, a quality factor of 98, a power consumption of 259 mW and a sensitivity of 259 nm·mTź1. This sensor design could have potential applications in non-destructive testing of ferromagnetic materials.

Characterization of system-related geometric distortions in MR images employed in Gamma Knife radiosurgery applications

This work provides characterization of system-related geometric distortions present in MRIs used in Gamma Knife (GK) stereotactic radiosurgery (SRS) treatment planning.A custom-made phantom, compatible with the Leksell stereotactic frame model G and encompassing 947 control points (CPs), was utilized. MR images were obtained with and without the frame, thus allowing discrimination of frame-induced distortions. In the absence of the frame and following compensation for field inhomogeneities, measured average CP disposition owing to gradient nonlinearities was 0.53 mm. In presence of the frame, contrarily, detected distortion was greatly increased (up to about 5 mm) in the vicinity of the frame base due to eddy currents induced in the closed loop of its aluminum material. Frame-related distortion was obliterated at approximately 90 mm from the frame base. Although the region with the maximum observed distortion may not lie within the GK treatable volume, the presence of the frame results in distortion of the order of 1.5 mm at a 7 cm distance from the center of the Leksell space. Additionally, severe distortions observed outside the treatable volume could possibly impinge on the delivery accuracy mainly by adversely affecting the registration process (e.g. the position of the lower part of the N-shaped fiducials used to define the stereotactic space may be miss-registered). Images acquired with a modified version of the frame developed by replacing its front side with an acrylic bar, thus interrupting the closed aluminum loop and reducing the induced eddy currents, were shown to benefit from relatively reduced distortion.System-related distortion was also identified in patient MR images. Using corresponding CT angiography images as a reference, an offset of 1.1 mm was detected for two vessels lying in close proximity to the frame base, while excellent spatial agreement was observed for a vessel far apart from the frame base.

Portable signal conditioning system of a MEMS magnetic field sensor for industrial applications

We present a portable signal conditioning system of a micromachined magnetic field sensor. This system, implemented on a printed circuit board, includes a new algorithm for two sinusoidal signal generators, which bias the magnetic field sensor. This algorithm uses the direct digital synthesis technique for two embedded peripheral interface microcontrollers. The magnetic field sensor consists of a resonant silicon structure (600 µm × 700 µm × 5 µm), an aluminum loop (1 µm thickness), and a Wheatstone bridge of four type-p piezoresistors. The two signal generators have a frequency stability of ±100 ppm and a resolution of 1 Hz. With this system, the magnetic field sensor has a linear approximately response in voltage mode as well as experimental sensitivity and resolution of 0.32 V Tź1 and 35 nT at atmospheric pressure, respectively. A virtual instrument is designed to visualize the output voltage of the magnetic field sensor. The signal conditioning system of the sensor could be used as industrial portable equipment to detect residual magnetic fields of ferromagnetic materials.

A MEMS-based magnetic field sensor with simple resonant structure and linear electrical response

We present a microelectromechanical system (MEMS)-based magnetic field sensor with simple structural configuration, low power consumption, and linear electrical response. This sensor operates with Lorentz force and uses piezoresistive sensing. Its resonant silicon structure consists of a perforated plate (472×300×15μm), four flexural beams (18×15×15μm), two support beams (60×36×15μm), and an aluminum loop (9×2μm cross-section), which are fabricated using a standard bulk micromachining process. The sensor works at its first seesaw resonant frequency without a vacuum packaging. Analytical and finite element method (FEM) models are developed to predict the mechanical behavior of the sensor structure considering the main damping sources. The experimental seesaw resonant frequency and quality factor of the sensor are 100.7kHz and 419.6, respectively. The sensor has a linear electrical response and its detection range can be easily adjusted. For a DC bias voltage (Vin) of 3V and a bandwidth of 240Hz, the sensor has sensitivity, resolution, and power consumption of 230 mV⋅T–1, 2.5μT, and 12mW, respectively. This sensor could be used in non-destructive magnetic testing for monitoring geometrical defects and corrosion of ferromagnetic materials.

Design and modeling of a novel microsensor to detect magnetic fields in two orthogonal directions

In this paper, we present the design and modeling of the electrical–mechanical behavior of a novel microsensor to detect magnetic fields in two orthogonal directions (2D). This microsensor uses a simple silicon resonant structure and a Wheatstone bridge with small p-type piezoresistors (10 × 4 × 1 μm) to improve the microsensor resolution. The resonant structure has two double-clamped silicon beams (1000 × 28 × 5 μm) and an aluminum loop (1 μm thickness). The microsensor design allows important advantages such as small size, compact structure, easy operation and signal processing, and high resolution. In addition, the microsensor design is suitable to fabricate using silicon on insulator (SOI) wafers in a standard bulk micromachining process. An analytical model is developed to predict the first bending resonant frequency of the microsensor structure using Macaulay and Rayleigh methods, as well as the Euler–Bernoulli beam theory. Air and intrinsic damping sources of the microsensor structure are considered for its electrical–mechanical response. The mechanical behavior of the microsensor is studied using finite element models (FEMs). For 10 mA of root mean square (RMS) excitation current and 10 Pa air pressure, this microsensor has a linear electrical response, a fundamental bending resonant frequency of 52,163 Hz, and a high theoretical resolution of 160 pT.

A mechanism controlling the production rate of freely migrating radiation-induced point defects in electron-irradiated metals

The temperature dependence of the production rate of radiation-induced point defects is found during the analysis of experimental data on nucleation and growth of dislocation interstitial loops in aluminum irradiated by 1 MeV electrons in the temperature range of 293–423 K. With elevation of the temperature, the production rate increases. The theoretical mechanism of the process is presented, which is in full agreement with the experimental data. The model and technique are developed for estimation of the maximum length of the sequence of focused atom collisions in irradiated solids. It is estimated to be equal to five lattice constants, which matches the results of theoretical evaluations obtained earlier using the computer simulation method.

Signal Conditioning System With a 4–20 mA Output for a Resonant Magnetic Field Sensor Based on MEMS Technology

Several resonant magnetic field sensors based on microelectromechanical systems (MEMS) technology use piezoresistive detection techniques to convert the magnetic field signal into an electrical signal. We present a signal conditioning system implemented in a printed circuit board (PCB) for a resonant magnetic field sensor based on MEMS technology. This sensor is formed by a resonant structure of thin silicon beams (5 μm thick), an aluminum loop (1 μm thick), and a Wheatstone bridge with four p-type piezoresistors. The Wheatstone bridge is biased with an alternating voltage of 2 Vpp at 1 kHz and the aluminum loop is supplied using an alternating current with a root-mean-square (RMS) value of 20 mA. This current is applied to the resonant frequency of the sensor (14.38 kHz) through an oscillator that has a frequency stability of ± 100 ppm at atmospheric temperature and a resolution of 1 Hz. The proposed system obtains the sensor's electrical response in voltage or current mode, which presents an approximately linear behavior for a range of magnetic field density from -150 to +150 μT. This system minimizes the offset of the sensor's electrical response and allows the detection of the polarity and magnitude of the magnetic field density. A virtual instrument is designed using Lab VIEW software to visualize the 4-20 mA output of the sensor. The designed system can help the development of portable measurement equipment to detect (at pressure atmospheric) low magnetic field densities with a sensitivity and resolution of 4 V · T-1 and 1 μT, respectively.

Design, Fabrication, and Characterization of a Resonant Magnetic Field Sensor Based on MEMS Technology

We present the design, fabrication, and characterization of a resonant magnetic field sensor based on Microelectromechanical systems (MEMS). This sensor exploits the Lorentz force principle and uses a Wheatstone bridge of p-type piezoresistors. Its resonant structure is integrated with silicon beams (15 μm wide and 5 μm thick) and an aluminum loop (9 μm wide and 1 μm thick). The sensor operates in its first flexural resonant frequency (22.99 kHz) and has a linear response, a high resolution (43 nT), a sensitivity of 1.94 V·T−1, a quality factor of 96.6 at atmospheric pressure, and power consumption close to 16 mW.

Enhancement and decrease of critical current due to suppression of superconductivity by a magnetic field

We present experimental results on the transport properties of a superconducting aluminum loop connected to reservoirs. As function of the applied magnetic field, an unexpected behavior is found—a steep enhancement for temperatures close to the critical temperature and a sharp drop at lower temperatures of the critical current at some value of the magnetic field Ba T. These effects are a consequence of a sudden suppression of superconductivity at Ba =B a in the banks to which the loop is attached by the current leads. As a result, the normal metal–superconductor boundaries appear at the ends of the current leads and the quasiparticle distribution function fE in the superconductor deviates strongly from its equilibrium value. Calculations based on the Usadel equations show that the critical current should be enhanced at high temperature due to the penetration of the normal current from the normal metal–superconductor boundaries, whereas at low temperatures, the suppression of the order parameter by the nonequilibrium fE dominates and the critical current decreases. The latter provides a direct experimental verification of the recently proposed mechanism of the destruction of superconductivity by an applied voltage R. S. Keizer, M. G. Flokstra, J. Aarts, and T. M. Klapwijk, Phys. Rev. Lett. 96, 147002 2006.

Attojoule Calorimetry of Mesoscopic Superconducting Loops

We report the first experimental evidence of nontrivial thermal behavior of the simplest mesoscopic system--a superconducting loop. By measuring the specific heat C of an array of 450,000 noninteracting aluminum loops with very high accuracy of approximately 20 fJ/K, we show that the loops go through a periodic sequence of phase transitions (with a period of an integer number of magnetic flux quanta) as the magnetic flux threading each loop is increased. The transitions are well described by the Ginzburg-Landau theory and are accompanied by discontinuities of C of only several thousands of Boltzmann constants kB.

Formation of stacking-fault tetrahedra in aluminum irradiated with high-energy particles at low-temperatures

Stacking-fault tetrahedra (SFT) are typical vacancy clusters in fcc metals. SFT have been, however, considered to be unstable in aluminum because of its high stacking-fault energy, until the recent finding of SFT in thin aluminum foils subjected to a tensile fracture. This study confirmed that SFT form in aluminum following irradiation with high-energy particles. In electron irradiation, SFT with an average size of 2 nm formed below 203 K, while a larger irradiation intensity at lower temperature induced SFT with a larger number density. Irradiation with 60-keV Al + ions induced SFT below room temperature, although the defect yield (the ratio of the number of defect clusters to the number of incident ions) was about 10 3 , considerably smaller than that in the other fcc pure metals. With neutron irradiation below 15 K to a fluence of 2 × 10 2 1 neutrons m - 2 , SFT were not observed at room temperature. Instead, dislocation loops were observed to form and to disappear during observation with 120-kV electrons that do not cause atomic displacements. Tensile fracture of aluminum thin foil induced SFT at up to 400 K, which is close to the temperature at which SFT become unstable in isochronal annealing experiments. These results suggest that a high concentration of vacancies at lower temperature tends to cause SFT to form rather than vacancy-type dislocation loops in aluminum.

Dilation of the giant vortex state in a mesoscopic superconducting loop

We have experimentally investigated the magnetization of a mesoscopic aluminum loop at temperatures well below the superconducting transition temperature ${T}_{c}.$ The flux quantization of the superconducting loop was investigated with a $\ensuremath{\mu}$-Hall magnetometer in magnetic field intensities between $\ifmmode\pm\else\textpm\fi{}100 \mathrm{G}.$ The magnetic field intensity periodicity observed in the magnetization measurements is expected to take integer values of the superconducting flux quanta ${\ensuremath{\Phi}}_{0}=h/2e.$ A closer inspection of the periodicity, however, reveals a subflux quantum shift. This fine structure we interpret as a consequence of a so-called giant vortex state nucleating towards either the inner or the outer side of the loop. These findings are in agreement with recent theoretical reports.

Highlights in the history of X-ray topography 1

Abstract X-ray topography provides a non-destructive method of mapping point-by-point variations in orientation and reflecting power within crystals. The discovery, made by several workers independently, that in nearly perfect crystals it was possible to detect individual dislocations by X-ray diffraction contrast started an epoch of rapid exploitation of X-ray topography as a new, general method for assessing crystal perfection. Another discovery, that of X-ray Pendellösung, led to important theoretical developments in X-ray diffraction theory and to a new and precise method for measuring structure factors on an absolute scale. Other highlights picked out for mention are studies of Frank-Read dislocation sources, the discovery of long dislocation helices and lines of coaxial dislocation loops in aluminium, of internal magnetic domain structures in Fe-3 wt.% Si, and of stacking faults in silicon and natural diamonds.

Effect of temperature and flux change on the behavior of radiation induced dislocation loops in pure aluminum

Specimens of annealed aluminum of 99.9999% nominal purity were irradiated with 400 keV electrons. Damage rates varied from 3.7 × 10 −4 to 3.7 × 10 −3 dpa/s. Irradiation temperatures were also stepwise varied in the range between 298 and 420 K. Irradiation at the lower temperatures caused to nucleate dislocation loops. Subsequent increase of the irradiation temperature resulted in contraction of loops in small sizes formed during the low temperature irradiation. This suggests that smaller loops have a smaller bias and/or capture efficiency for interstitials. Results also suggest that temperature changes can accelerate swelling and irradiation hardening.

Quantum interference in a mesoscopic superconducting loop

THE classical superconducting quantum interference device (SQUID) is based on the Josephson effect1, and usually consists of a macroscopic superconducting loop with two artificial weak links (Josephson junctions) through which the supercurrent passes by quantum-mechanical tunnelling. Fink et al.2 proposed a new type of SQUID based on a homogeneous mesoscopic superconducting loop, in which interference between the supercurrents passing through the two halves of the ring results in a critical current that varies with the applied magnetic field in an oscillatory manner. Here we describe the experimental observation of these oscillations in a mesoscopic superconducting aluminum loop without artificial weak links. In this new type of quantum interferometer, 'weak-link' regions with a strongly reduced superconducting order parameter appear periodically at half-integer magnetic flux quanta owing to the interplay between the shielding and transport currents in the loop.