Copper Channels Research Articles

Low temperature spin relaxation length exceeding 3 μm in highly conductive copper channels

Despite extensive studies of spin transport in metallic structures, it remains a challenge to achieve spin relaxation length well above 1 μm in metals even at low temperatures. We explore nonlocal spin transport in Cu channels with a cross section of 0.5 × 0.5 μm2, which exhibit superior values of electrical conductivity and residual resistivity ratio (RRR). Based on structures fabricated in a single batch, we found an average spin relaxation length of λCu=3.2±0.7μm and an average spin relaxation time of τs = 120 ± 50 ps at 30 K. Substantial variations of λCu, RRR, and resistivity ρCu are found among the structures and the three quantities correlate well to one another. The most conductive Cu channel in the batch yields λCu=5.3±0.8μm and τs=250±80ps. These superior values exceed expectations for metals and can be attributed to reduced spin relaxation from grain boundaries and surfaces.

Influence of fusion welding processes on microstructure and mechanical properties of dissimilar metal (AISI 304 SS-Copper) weldment

Dissimilar metal welding of AISI 304 stainless steel (304 SS) and commercially pure copper (CP copper) has been taken up to understand the influence of the different fusion welding processes on microstructure and mechanical properties of the weldment. The fusion welding processes specifically involve continuous wave CO2 laser, pulsed wave Nd: YAG laser and pulsed wave tungsten inert gas (P-TIG) welding. The primary objective of the present work is to develop a successful weld between two dissimilar metals without using any filler material by different fusion welding processes. An overall comparison of the results obtained from different sets of analyses is represented. The optical image of the top surface of the weld revealed that the no spatter formation during CO2 laser and P-TIG welding process, whereas minimal spatter for Nd: YAG laser. In comparison to laser processes, the weld face formed by P-TIG welding was much wider. However, 100 % penetration was achieved with all three types of welding. The average widths of heat affected zone (HAZ) found to be 10 µm and 23 µm for CO2 and Nd:YAG laser respectively. The way the microstructure changes at the fusion zone was the same in all cases. For example, copper channels form, dendrites grow epitaxially, etc. SEM pictures indicate the Cu tubular channels observed more often for P-TIG welding. The microhardness distribution in the weld zone was found to be larger than that of copper and close to that of 304 SS. The acceptable ultimate tensile stress (UTS) for dissimilar metal welding of SS-Cu couples was found 275 MPa, 278 MPa and 195 MPa for CO2 laser, P-TIG and Nd:YAG laser respectively.

Enhanced internal condensation of R1233zd(E) on micro- and nanostructured copper and aluminum surfaces

In-tube condensation of refrigerants is an important process which affects thermal efficiency in many applications, ranging from refrigeration and air conditioning to electronics thermal management. In-tube heat transfer and pressure drop are important to heat exchanger sizing and design. In this work, micro- and nanostructured surfaces are applied to the internal wetted areas of copper and aluminum mini-channels to enhance the condensation heat transfer coefficient of hydrofluorocarbon R1233zd(E) refrigerant. To achieve scalable nanomanufacturing, surfaces were uniformly structured by relying on hydrochloric acid etching of aluminum and chemical oxidation of copper. The etched aluminum surfaces exhibited a 150% increase in heat transfer coefficient compared to smooth aluminum channels at specific qualities, with a 66% heat transfer coefficient improvement for complete phase change from saturated vapor to saturated liquid. Copper oxide structures showed no discernable difference in thermal-hydraulic performance when compared to smooth copper channels. Critical dimensionless parameters governing the heat transfer enhancement were identified by varying the tube internal diameter (2.3 mm to 4.7 mm), refrigerant mass flux (50 to 300 kg/(m2·s)), and refrigerant quality (0 to 1). The dimensionless parameters include the Bond number normalized to the condensate film thickness, and the Weber number modified by the vapor friction factor. The relatively small increase in pressure drop (< 10%) associated with these surface enhancements further supports the promise of this method. The scalable and cost-effective techniques used to create these aluminum microstructures may reduce manufacturing cost when compared with current enhancement approaches such as extrusion, drawing, and welding.

Spin relaxation in copper channels with submicron cross sections

We review our recent experimental studies of the spin relaxation processes in the submicron copper channels of nonlocal spin valves (NLSV). Long spin relaxation lengths up to 3.0 μm at low temperatures are demonstrated in highly conductive copper channels with residual resistivity ratios up to 6. An unexpected anisotropy of spin relaxation is observed and can be attributed to the surface spin–orbit effects. An unusual scaling of the Kondo spin relaxation is established experimentally and can be explained by overlapping Kondo screening clouds. Our results demonstrate the technological potential of copper as a spin transport channel in spintronics and highlights unanswered fundamental questions related to the spin relaxation processes.

Thermo-Fluid Physiognomies of a Photovoltaic Thermal Collector: A Comparative Study With Different Flow Channel Materials

Abstract In recent years, a good number of research works have been conducted to elucidate the different aspects of photovoltaic thermal (PV/T) technology. However, in order to take a technology to its maturity level, it is important to explore its internal physics and identify the factors that control system performance. With this view, in the present research, thermal and heat transfer characterization, and pressure drop phenomena inside a parallel-plate PV/T collector have been examined numerically to portray the thermo-fluid physiognomy of the system. A three-dimensional mathematical model of the PV/T system has been developed, and the model is used to build a computer simulation of the system in COMSOL Multiphysics® software. Hence, the simulation model has been validated by outdoor experimental results and was found to be in good agreement. Thus, the simulation program is employed to produce temperature distribution and heat flow plots throughout the flow channel, wherein results have been evaluated for two different channel materials, e.g., aluminum and copper. Results show that heat flowrate through both aluminum and copper channels is virtually the same. On the other hand, pressure drop, thereby pumping power required to maintain flow, is greater for an aluminum channel. The developed heat transfer simulation model can be extended for other PV modules with diverse designs and materials of the heat exchanger.

Experimental and numerical analyses of fluid flow inside additively manufactured and smoothed cooling channels

The surface roughness can be considered one of the main drawbacks of the Laser Powder Bed Fusion (LPBF) technology applied to thermal applications. Favero et al. [1] experimentally and numerically demonstrated that the surface roughness of printed copper channels deeply affects their fluid dynamic performance and limits the predictive capabilities of the CFD tools. The authors proposed a methodology to calibrate the numerical tools in turbulent flow. However, the problem remains unsolved because the printed copper channels exhibit remarkably higher pressure drops when compared to conventional smooth channels, hindering the proper deployment of the technology in the thermal sector. This paper proves how it is possible to smooth the internal walls of channels obtained via LPBF to reduce the surface roughness. In fact, the chemical milling process is proposed and applied. The smoothed channels showed a fluid dynamic behaviour similar to the conventional ones. Finally, by coupling Computer Tomography to the CFD tool, the fluid dynamic behaviour inside the smoothed channels is fairly predicted, confirming that the surface roughness and the channel dimensions are the controlling parameters of the fluid dynamic performance of channels printed via LPBF.

Fiber-Extended Copper Line Architecture With End-to-End Data Transmission and Link Monitoring

We demonstrate a prototype hybrid, full duplex fiber-extended copper line with frequency-reusability and simultaneous fiber and copper line monitoring. The link architecture is composed of three main units: a central office; a remote-node copper to fiber converter (CuFiC); and a radio head. A fiber optical link connects the central office to the remote node, while the remote node is connected to the radio head by a copper line. Even though the prototype is built with two full duplex channels, more channels can be supported by the architecture, and an optical feedforward linearization scheme for the transmitter is demonstrated for that purpose. In-service simultaneous multi-copper and fiber monitoring is possible with the right choice of frequency bands, a result backed by the Error Vector Magnitude measurement of data channels in simultaneous coexistence with monitoring channels. A frequency multiplication unit, built into both the transmitter and the remote node, allows for a single seed tone to generate all the sub-carrier multiplexed channels for up and downstream in both the fiber and in the copper links without the need of local oscillators. This not only simplifies the architecture, but also allows for optimal homodyne up- /down-conversion. The demonstrated prototype figures as a potential candidate for interfacing fiber to the home and fiber to the building (FTTH/FTTB) links with legacy copper infrastructure currently allowing for: up to eight 20MHz LTE 64QAM channels to be subcarrier-multiplexed onto a single optical carrier and seemlessly demultiplexed into individual copper channels, backed by a ≤8% EVM measured at the radio head; concurrent 7dB dynamic range 10 meter spatial resolution intermediate-haul fiber monitoring (up to 15 km) as well as copper line monitoring both available at the central office. The next steps beyond the presented proof of concept include simultaneous bi-directional transmission among multiple receivers, automated feed-forward linearization, and the study of factors that may limit the achievable dynamic range.

The effect of microstructural aspects of W[sbnd]Cu composites on electrical conductivity and thermal erosion

Molten copper infiltration through tungsten skeleton produces WCu composites with versatile applications. In this research, the compressibility and sintering of three W powders with different particle sizes (fine: 1.2 μm, medium: 6 μm, coarse: 8.5 μm) were studied, and 80 vol%W composite specimens were produced from the various primary tungsten powders. The microstructure and electrical conductivity of composites were examined, and a model was successfully developed to establish a relationship between microstructural aspects and electrical conductivity. In addition, the WCu composites were exposed to a high-velocity oxyacetylene flame to evaluate the thermal erosion resistance. Results showed that in addition to density, microstructural aspects have significant effects on conductivity and thermal erosion resistance of WCu composites. The larger copper channels in WCu composites provided higher conductivity and also higher erosion resistance. In addition, the uniformity of channels walls had the same effects. These microstructural aspects affected on evaporation of the copper phase and the transpiration cooling.

Scaling of Kondo spin relaxation: Experiments on Cu-based nonlocal spin valves with Fe impurities

The relation between the Kondo spin-relaxation rate ${{\ensuremath{\tau}}_{sK}}^{\ensuremath{-}1}$ and the Kondo momentum-relaxation rate ${{\ensuremath{\tau}}_{eK}}^{\ensuremath{-}1}$ is explored by using nonlocal spin valves with submicron copper channels that contain dilute iron impurities. A linear relation between ${{\ensuremath{\tau}}_{sK}}^{\ensuremath{-}1}$ and ${{\ensuremath{\tau}}_{eK}}^{\ensuremath{-}1}$ is established under varying temperatures for any given device. Among 20 devices, however, ${{\ensuremath{\tau}}_{sK}}^{\ensuremath{-}1}$ remains nearly constant, despite variation of ${{\ensuremath{\tau}}_{eK}}^{\ensuremath{-}1}$ by a factor of 10. This surprising relation can be understood by considering spin relaxation through overlapping Kondo screening clouds and supports the physical existence of the elusive Kondo clouds.

Additive manufacturing for thermal management applications: from experimental results to numerical modeling

Recently, Additive Manufacturing (AM) of metal components has opened new frontiers in heat transfer applications, going beyond the capabilities of conventional technologies. Despite the great design freedom offered by AM, when dealing with metals, there are a few issues that should be considered to exploit the great capabilities of this manufacturing technology. In fact, the surface roughness of the components is expected to affect the performance of the devices, which can be remarkably different from the ones simulated with computer codes. This paper presents a critical analysis of the accuracy of the numerical tools to simulate the fluid flow behaviour inside channels obtained via AM, showing the major limitations of the standard approaches to accurately predict the pressure drops in straight and complex channels. Three different copper channels of growing complexity were built via SLM (Selective Laser Melting) and then they were experimentally tested to evaluate the predictive abilities of the numerical model. The results revealed that the surface roughness deeply affects the fluid flow, thus the numerical models need to be calibrated to become reliable design tools. The proposed procedure can be considered the first attempt in this direction and allows for a proper integration of the AM with the numerical simulation tools to boost the design capabilities of SLM technology.

Effect of gradient wettability on capillary imbibition in open semicircular copper channel

Open semicircular copper channels with a gradient wettability of 45°–3° or 3°–45° (contact angle of 1,2-propanediol), homogeneous wettability of 3°, and segmented wettability on their inner surfaces were constructed. The capillary imbibition of 1,2-propanediol in these channels demonstrates that, compared with the surface with homogeneous wettability, there are an additional driving force and resistance on the surfaces with a gradient wettability of 45°–3° and 3°–45°, respectively. Meanwhile, the channel with gradient wettability on the first half segment and homogeneous wettability on the second half segment could accelerate capillary imbibition better than that with gradient wettability on the whole channel. Furthermore, a smaller length ratio, i.e., length of gradient segment to that of homogeneous segment of the channel, demonstrates a better liquid acceleration effect. Based on the Lucas–Washburn equation, a theoretical model to describe capillary imbibition was established by introducing an additional force arisen from the positive gradient wettability and a retardation coefficient caused by the surface roughness. The flow front position vs flow time could be predicted by the established model in this work, and the relative error between the theoretical prediction and experimental result was less than 20.7%, indicating the rationality of the proposed model.

Investigation of the thermal effect of a tubular permanent magnet actuator with a water cooling channel for active lateral suspension of a high-speed train

Worldwide, high-speed rail is becoming an increasingly popular and efficient means of transport. However, increasing the speed of a train leads to major reductions in stability and ride comfort. Here, we develop a tubular permanent magnet actuator to overcome these problems. To increase actuator thrust, the electromagnetic circuit requires a high current and, thus, becomes hot. We use a water cooling system with 12 straight copper channels to reduce the temperature. We calculate heat transfer coefficients using empirical convection correlations between laminar flow in the channels and experimental results. The predicted, tube surface temperatures correlated well with the experimental data. We evaluated the effects of flow rate and initial water temperature on various design parameters. The cooling system allowed application of a current greater than 100 A, developing a thrust force of over 8000 N. Thus, the system was robust under harsh operating conditions. We measured the thrust and cogging forces and the performance of the water cooling system in terms of the maximum acceptable temperature. The thrust was high and the cogging torque was low, greatly reducing lateral vibration; the temperature remained below the acceptable maximum.

Chord Signaling for High-Speed Data Movement: Employing Advanced Communication and Circuit Techniques to Augment Data-Transfer Bandwidth

This article presents a class of signaling methods that improves the data rate of communication over copper channels without compromising its sensitivity to intersymbol interference (ISI). Chord signaling (CS) [1], [2] puts correlated data over multiple wires to improve the overall data-transfer bandwidth (BW), while maintaining resilience against common-mode (CM) and crosstalk (XTALK) noise, without adding circuit complexities. As a generalized form of differential signaling (DS), CS exploits proper spatial (multiwire) signaling to improve the aggregated BW and relax the required amount of equalization.

Organ‑specific expression of the divalent ion channel proteins NCKX3, TRPV2, CTR1, ATP7A, IREG1 and HEPH in various canine organs.

Transmembrane cation channels include those for calcium, copper and iron ion transport. Each channel has physiological significance, and all have been associated with disease. However, the comparative study of transcriptional‑translational levels in canine organs has not been previously reported. In the present study, organ‑specific expression of calcium channels, including sodium/potassium/calcium exchanger 3 (NCKX3) and transient receptor potential cation channel subfamilyV member 2 (TRPV2), copper channels, including high affinity copper uptake protein 1 (CTR1) and copper‑transporting ATPase 1 (ATP7A), and iron channels, including iron‑regulated transporter 1 (IREG1) and hephaestin (HEPH) proteins and their mRNAs were examined in the canine duodenum, kidney, spleen and liver. NCKX3 protein expression was highest in the kidney, moderate in the duodenum, and lowest in the spleen and liver, whereas TRPV2 protein was highly expressed in the kidney, duodenum and liver, and was low in the spleen. The CTR1 protein expression level was highest in the liver, followed (in descending order) by the duodenum, kidney and spleen. The ATP7A protein expression level was highest in the duodenum and lowest in the spleen. The IREG1 protein expression level was highest in the liver, followed (in descending order) by the kidney, duodenum and spleen. The HEPH protein level was high in liver, moderate in the duodenum and kidney, and low in the spleen. The results of the immunohistochemistry analysis demonstrated ion channel protein localizations. These results suggested that cation channel proteins are differentially expressed among canine organs, and they may be involved in organ‑specific functions associated with the maintenance of physiological homeostasis.

A Three-Dimensional Comprehensive Numerical Investigation of Different Operating Parameters on the Performance of a Photovoltaic Thermal System With Pancake Collector

Performance of photovoltaic (PV) module decreases significantly with increasing cell temperature due to its overheating. Photovoltaic thermal (PVT) is an optimized technology that facilitates effective removal and utilization of this excess heat leading to enhanced electrical performance. In this article, a 3D numerical model has been developed and analyzed to investigate the PVT performance with a new pancake-shaped flow channel design. This flow channel is attached directly to the backside of PV module by using thermal paste. The governing equations are solved numerically by using Galerkin's weighted residual finite-element method (FEM), which has been developed using COMSOL Multiphysics® software. The numerical results show that the cell temperature reduces on an average 42 °C, and the electrical efficiency and output power increase by 2% and 20 W, respectively, for both aluminum and copper channels with an increase in inlet velocity from 0.0009 to 0.05 m/s. On the other hand, overall efficiency of the PVT system drops about 13% in both cases as the inlet temperature increases from 20 °C to 40 °C. Cell temperature is found to increase approximately by 5.4 °C and 9.2 °C for every 100 W/m2 increase in irradiation level of the PV module with and without cooling system, respectively. Regarding flow channel material, it has been observed that use of either copper or aluminum produces almost similar performance of the PVT module.

Expanded Constellation Mapping for Enhanced Far-End-Cross-Talk Cancellation in G.fast

We propose the novel concept of expanded constellation mapping (ECM) for maximising the received signal power, while cancelling the far-end-cross-talk in copper-based wireline communications. The goal of ECM is to beneficially map the transmitted symbol vector to its expanded constellation set by carefully exploiting the copper channels’ specific characteristics. To elaborate, ECM is comprised of the control entity and of the match entity, where the former determines how the ECM would be applied, while the latter searches for the best mapping of the transmitted symbol vector to the expanded constellation set. Our numerical results demonstrate that with the aid of the ECM, more than 25-dB power efficiency gain may be achieved over linear vectoring. Similarly, about 20-dB gain may be achieved over non-linear vectoring. From an implementation point of view, the ECM imposes minimal structural changes on G.fast, whilst exhibiting beneficial reconfigurability and compatibility.

Effects of Octylphenol and Bisphenol A on the Metal Cation Transporter Channels of Mouse Placentas.

Octylphenol (OP) and bisphenol A (BPA) are known as endocrine-disrupting chemicals (EDCs). During pregnancy, the expression of steroid hormone receptors is controlled by maternal and fetal nutrition. To evaluate the impact of EDCs during pregnancy, ethinyl estradiol (EE, 0.2 mg/kg/day), OP (50 mg/kg/day), and BPA (50 mg/kg/day) were administered to pregnant mice. The mRNA levels of TRPV6 (transient receptor potential cation channels in subfamily V, member 6) decreased significantly by EE and OP. The PMCA1 (ATPase, Ca++ transporting, plasma membrane 1) mRNA and protein levels decreased significantly by EE, OP, and BPA. CTR1 (solute carrier family 31, member 1) and ATP7A (ATPase, Cu++ transporting, alpha polypeptide) expression decreased significantly by EE, OP, and BPA. The mRNA levels of IREG1 (iron-regulated transporter, member 1) decreased significantly by EE. Hephaestin (HEPH) mRNA levels decreased significantly by EE, OP, and BPA, and protein levels decreased significantly by BPA. As a result of immunohistochemistry analysis, all cation transporter proteins were found in labyrinth of placenta. To confirm the cytosolic level of cations, levels of cation level in fetal serum were measured. EE, OP, and BPA significantly reduced serum calcium and copper levels, and iron levels were reduced by BPA. Taken together, some EDCs, such as OP and BPA, could modulate the calcium, copper, and iron ion-transporting channels during pregnancy. The fetus relies on the mother for ionic transportation, and, therefore, pregnant women should avoid exposure to cation-channel-disrupting chemicals.

Failure Investigation of Cooling Plates of a Blast Furnace

Premature failure of cooling plates of a blast furnace in service has been investigated. The cooling plates are water-cooled copper channels shielded by refractory lining. Industrial cooling water (ICW) flows at 5 bar pressure through the cooling plates. The investigation consisted of visual inspection, chemical analysis, microstructural examination by optical microscopy, energy-dispersive spectroscopy (EDS), and hardness measurement. Visual inspection revealed that the refractory lining on the component was damaged, thereby exposing the cooling plates to elevated temperatures of the furnace atmosphere. This led to overheating of the cooling plates. Chemical analysis revealed that the component was essentially pure copper (~99.24% purity). Microstructural analysis showed grain size variation across the section of the component. Also, annealing twins were revealed on optical examination. A through-thickness pit was identified on the failed component during the optical examination. The examination also revealed branched cracks associated with scale in the component. Energy-dispersive spectroscopy (EDS) confirmed the scale to be oxides indicating high-temperature oxidation of the component resulting in pitting. Analysis suggested overheating due to damage of the refractory lining as the prime cause of failure of the component.

A 10.3-GS/s, 6-Bit Flash ADC for 10G Ethernet Applications

This paper presents the design of a 40-nm CMOS 10.3-GS/s 6-bit Flash ADC used as the analog frontend of a universal DSP-based receiver that meets the requirements for all the NRZ 10G Ethernet (10GE) standards, for both fiber and copper channels. The 4-way interleaved ADC consists of a pair of frontend variable gain amplifiers (VGAs) driving four sets of track-and-hold (T/H) switches, followed by fine VGAs that drive 6-bit comparator arrays. A Wallace-tree adder is utilized as the thermometer-to-binary encoder allowing comparator re-ordering and redundancy. Also integrated is an 8-bit calibration DAC that is used as a reference to nullify the accumulated offset of the entire signal path, as well as to compensate for the nominal nonlinearity of the fine VGA and the resistor ladder. After calibration, the peak SNDR of the ADC is about 34 dB with bandwidth ranging from 3.5 to 6 GHz over all VGA gain settings. The ADC, along with its entire clock path, occupies 0.27 mm <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$^{2}$</tex></formula> and consumes 242 mW from a 0.9-V supply.

Giga-bit CMOS equalizers for high-speed data links

Consumer electronics are experiencing an explosive growth in bandwidth requirements. This growth is driven by demand for fiber-to-the-home Internet connections, the increasing capabilities of in-home consumer devices as well as the demands of multimedia recording and playback in mobile devices. However, traditional copper channels and previous generations of optical fiber experience dispersive effects at data rates above 1 Gbps, leading to inter-symbol interference (ISI). This paper presents a finite impulse response filter-based feed forward equalizer (FFE) to reduce the effect of ISI on these channels. The efficacy is of the FFE is demonstrated by measuring the eye diagrams of a 10 Gbps signal transmitted through an optical fiber as well as a copper backplane with and without FFE compensation. The proposed FFEs successfully compensate ISI for both the optical and copper backplane links. All circuits are fabricated using a 0.18 μm CMOS process.