Arc Diameter Research Articles

Compact compressive arc and beam switchyard for energy recovery linac-driven ultraviolet free electron lasers

High gain free electron lasers (FELs) driven by high repetition rate recirculating accelerators have received considerable attention in the scientific and industrial communities in recent years. Cost-performance optimization of such facilities encourages limiting machine size and complexity, and a compact machine can be realized by combining bending and bunch length compression during the last stage of recirculation, just before lasing. The impact of coherent synchrotron radiation (CSR) on electron beam quality during compression can, however, limit FEL output power. When methods to counteract CSR are implemented, appropriate beam diagnostics become critical to ensure that the target beam parameters are met before lasing, as well as to guarantee reliable, predictable performance and rapid machine setup and recovery. This article describes a beam line for bunch compression and recirculation, and beam switchyard accessing a diagnostic line for EUV lasing at 1 GeV beam energy. The footprint is modest, with 12 m compressive arc diameter and $\ensuremath{\sim}20\text{ }\text{ }\mathrm{m}$ diagnostic line length. The design limits beam quality degradation due to CSR both in the compressor and in the switchyard. Advantages and drawbacks of two switchyard lines providing, respectively, off-line and on-line measurements are discussed. The entire design is scalable to different beam energies and charges.

Surface Temperature Analysis of Transversal Magnetic Field Contacts Using a Thermography Camera

Some vacuum interrupters (VIs) are equipped with transversal magnetic field contacts. A transversal directed Lorentz force makes the arc move circularly. The local surface temperature of the arc root is usually above the melting point at high current. The temperature of the heated and molten contact surface of a VI can be measured using a high-speed thermography camera. We present a methodology for determining the surface temperature. For this purpose, the emissivity of the contact material must be known. For Cu, we determined the emissivity at $\varepsilon _{\mathrm {liq}} = 0.053$ (liquid) and $\varepsilon _{\mathrm {sol}} = 0.035$ (solid) for a spectral wavelength range of 1.5–1.7 $\mu \text{m}$ . Switching tests were performed using spiral contacts (CuCr 75/25) with a diameter of 68 mm and a 50-Hz half-wave sinusoidal current of 19 kA (rms). We examined the temperature of cooling anode spots of two different switching tests with various arc burning times and arc diameter. During the cooling phase of the anode spots, we observed a plateau in temperature at both measurements with different slope and duration. The plateaus started at the liquidus temperature of 1903 K of CuCr 75/25.

Comparative study on extinction process of gas-blasted air and CO2 arc discharge using two-dimensional electron density imaging sensor

Shack–Hartmann type laser wavefront sensors were applied to gas-blasted arc discharges under current-zero phases, generated in a 50 mm-long interelectrode gap confined by a gas flow nozzle, in order to conduct a systematic comparison of electron density decaying processes for two kinds of arc-quenching gas media: air and . The experimental results for the air and arc plasmas showed that the electron densities and arc diameters became thinner toward the nozzle-throat inlet due to a stronger convection loss in the arc radial direction. In addition, had a shorter electron density decaying time constant than air, which could be caused by convection loss and turbulent flow of stronger than air.

Free or confined arc model relevant to the quench hazard of large superconducting coils

This arc model was motivated by the need to model arcs during the failure of a large superconducting magnet following an unmitigated quench. During a quench, resistive heating raises the conductor and insulator temperature. Electrical and mechanical properties change and inline and bypass arcs can form. The arcs are sustained by the massive (gigaJoule) stored magnetic energy. As windings are bypassed by shorts, the inline arc current and hence, arc diameter, increases. Cable-in-conduit conductors limit the maximum arc column diameter and when limited, the arc properties change rapidly as the arc changes from a free arc to a confined arc. For arc current 10–100kA we calculate the arc column electrical properties and temperature, by solving a set of equations describing the arc physics. The equations describe the arc column heating, gas ionisation, heat loss and electrical properties. By constraining the maximum arc column diameter in the solution, the transition between free and confined arc can be calculated.

Properties of Vacuum Arc Influenced by Electrode Diameter and Material in TMF Contact Based on Forced Current Zero

With the increase in electrical equipment in More/All Electric Aircraft, 270 V dc power supply systems will be needed. One method for DC interruption is forced current zero (FCZ). Based on FCZ technology with transverse-magnetic-field (TMF) contact, the spiral-type contacts are designed. Experiments with different currents are carried out with contact diameters being 30 mm, 40 mm, and 50 mm, and arcing surface materials Cu-W80 alloy and Cu-Cr50 alloy respectively. It is indicated by the experimental results that breaking capacity of vacuum interrupter and vacuum arc appearance are closely related to the electrode diameter and material. For the same size of electrode diameter, the breaking capacity in Cu-Cr50 is better than that in Cu-W80. With increasing electrode diameter, arc column expansion velocity and diameter increase gradually. Breaking capacity is increasing with larger contact diameter.

Effect of Laser Cladding Al Ni TiC Powder on Microstructure and Properties of Aluminum Alloy

In this paper, Al/Ni/TiC powders were mixed on the surface of A380 aluminum alloy, by selecting appropriate laser parameters; the cladding layer with good adhesion to the substrate was obtained. The microstructure and properties of the cladding layer under different laser parameters were analyzed. The results show that: the phase composition of the cladding layer is mainly composed of TiC, Al, Ni, C and Ti phases. The hardness of the cladding region is up to 173.3 HV, which is about 2.9 times the matrix (–59.1 HV). The corrosion voltage (–1.8 V) of the cladding layer shifted significantly from the corrosion potential (–1.18 V), the corrosion current density increased, the resistance value decreased and the diameter of the capacitor arc decreased; all these phenomena indicate that the corrosion resistance of the cladding layer is decreased.

Compressive failure modes and parameter optimization of the trabecular structure of biomimetic fully integrated honeycomb plates

To develop lightweight biomimetic composite structures, the compressive failure and mechanical properties of fully integrated honeycomb plates were investigated experimentally and through the finite element method. The results indicated that: fracturing of the fully integrated honeycomb plates primarily occurred in the core layer, including the sealing edge structure. The morphological failures can be classified into two types, namely dislocations and compactions, and were caused primarily by the stress concentrations at the interfaces between the core layer and the upper and lower laminations and secondarily by the disordered short-fiber distribution in the material; although the fully integrated honeycomb plates manufactured in this experiment were imperfect, their mass-specific compressive strength was superior to that of similar biomimetic samples. Therefore, the proposed bio-inspired structure possesses good overall mechanical properties, and a range of parameters, such as the diameter of the transition arc, was defined for enhancing the design of fully integrated honeycomb plates and improving their compressive mechanical properties.

An Improved Arc Model Based on the Arc Diameter

This paper introduces an improved electrical arc model based on the arc diameter variation. In the conventional arc models, the arc diameter is considered as an implicit parameter in arc model constants. In case of decreasing arc diameter along with the arc extinction, the arc voltage decreases as well. The arc diameter can be implemented as a function of current into the arc model. The results illustrate that by applying the arc diameter as a function of arc current in the arc model, the simulated arc voltage is much closer to the measured values. In particular, the arc voltage behavior at the zero crossing can be controlled more precisely. However, based on the model considered for the arc diameter, additional parameters of the arc model should be estimated using measured data. The results confirm that even applying a simple arc diameter model can improve the arc voltage simulation.

Characterization of carbonation behavior of fly ash blended cement materials by the electrochemical impedance spectroscopy method

The carbonation behavior of fly ash blended cement materials is studied by the electrochemical impedance spectroscopy (EIS) method, and a novel equivalent circuit model Rs(Q1(Rct1W1)) (Q2(Rct2W2)) is proposed to investigate the influence of fly ash on the carbonation process in the cementitious materials. The experimental results demonstrate that the diameter of the impedance arc in high frequency region increases as carbonation progresses. Increasing the amount of fly ash incorporated in the cement paste is also found to enlarge the high frequency arc. The carbonation process can be quantified by the parameter Rct2 extracted from the equivalent circuit model Rs(Q1(Rct1W1)) (Q2(Rct2W2)). It is found that the Rct2 value increases with increase in fly ash content. A linear relationship between the Rct2 value and the carbonation time is also observed. As a consequence, prediction of the carbonation depth of fly ash bended cement materials can be achieved through knowledge of the Rct2 value.

Studies on the medium-frequency impedance arc for Lithium-ion batteries considering various alternating current amplitudes

An impedance measurement approach with various current amplitudes is proposed to investigate the impedance behavior of power Lithium-ion battery in the frequency domain. Notably, the impedance arc is divided into amplitude-independent response in the high-frequency range and amplitude-dependent response in medium-frequency range. A shrinking of semi-circle diameter of the impedance arc at medium-frequency part of measured spectrum is distinctly observed with rising current amplitude. Thus, a series of particular experiments are performed to facilitate the interpretation of the phenomenon. The possible influencing factors for the battery, including its state of charge, internal pressure, and temperature rise during the high-rate short-time charge/discharge, are illustrated and excluded for analysis, respectively. Based on the analysis of Butler-Volmer equation and Arrhenius empirical equation, a formula, which contains temperature and current known to influence the charge-transfer resistance, is derived logically. It indicates that the charge-transfer resistance reduces as the current amplitude increases at a fixed temperature, which fundamentally dominates the shrinking of the semi-circle at medium frequencies. Therefore, the medium-frequency impedance arc is able to represent the chemical reaction process, even under large current excitation (within a certain range).

Electrical Arc Model Based on Physical Parameters and Power Calculation

This paper presents an electrical arc model based on physical parameters of the arc including temperature, enthalpy, pressure, and also arc geometry. In this model, different mass flows and power losses are considered. The different powers including radiative and turbulent power as well as power gain and loss carried by axial and radial mass flows are calculated and simulated as a function of physical parameters. Moreover, the different arc diameter expressions and their influence on power losses are examined by arc experiments with high-speed imaging and arc dynamic behavior analysis. This model can provide the dynamic behavior of the arc easier in contrast to more complex physical models. The comparison with conventional arc models, such as Schwamaker, Habedank, Kema, and Schwarz, illustrates that the new arc model can better reproduce electrical measurements.

Process modeling of electrodes in proton exchange membrane fuel cells

The impedance characteristics of the activation and mass transport overpotentials in a proton exchange membrane fuel cell are determined analytically using a process model. The anode and cathode electrodes are studied separately. The governing equations are solved analytically and the resultant impedances and hence the equivalent circuits are extracted. The results show an excellent agreement between the analytical model and different measured impedances reported in the literature for various operating conditions and anode/cathode feedings. It is shown that the high frequency arc is the result of the anode impedance and is not a function of the current density. On the other hand, the mid-frequency arc consisting of two convoluted depressed semi-circles is the result of the cathode impedance. The solution clarifies the reason for an initial decrease followed by an increase in the diameter of the mid-frequency arc as the current density increases. The results also show that cathode starvation can be studied clearly from the mid frequency arc.

Numerical analysis on air entrapment during droplet impacting on a wetted surface

A numerical model is developed using the coupled level set and volume of fluid method including heat transfer and contact resistance to simulate air entrapment during a droplet impacting on a wetted surface. The dynamic characteristics of the phase interface are analysed. The mechanisms of deformation of the phase interface and formation of entrapped air are explored. The effects of impacting velocity and thickness of liquid film on characteristics of entrapped air are studied. The mechanism of heat transfer is also obtained in this article. The obtained results are as follows. The pressure difference between liquid and gas before the droplet impacting is the main factor determining the deformation of phases interface and the formation of air entrapment. The larger the impacting velocity, the larger the pressure inside the compressed air film is. When the droplet contacts the liquid film, the velocities of the droplet and liquid film increase to their maximum values, and at the impacting axis, they are approximately the same, nearly half the impacting velocity. The velocity distributions of phase interface of the droplet and liquid film are nearly the same in the area of impacting center. The impacting velocity has important effects on the dimensionless arc from bottom to breaking point and the dimensionless diameter of the air. The dimensionless arc and dimensionless diameter decrease with increasing impacting velocity. The dimensionless deforming heights of the droplet and liquid film are closely related to Stokes number: the larger the Stokes number, the larger the dimensionless deforming heights are, and they can be expressed as a power function with Stokes number. The initial thickness of liquid film also affects dimensionless deforming heights of the droplet and liquid film and dimensionless diameter of the entrapped air: the larger the dimensionless thickness of the liquid film, the larger the dimensionless deforming heights are, and the dimensionless diameter decreases with increasing dimensionless thickness of the liquid film. At the very initial stage of the impact, the entrapped air is important for surface heat flux distribution. The entrapped air presents contraction, breakup and detachment. The surface heat flux distribution changes closely with evolution of the entrapped air and tends to be uniform. The effect of the entrapped air on the surface heat flux distribution decreases gradually.

Study on Dynamic Characteristic in Force Interrupted DC Vacuum Arc

In this paper, the characteristic of 270 V dc forcing interruption is studied. The experiments are performed on a synthetic test circuit, under 1400 and 2000 A current, with the CuCr electrode vacuum interrupter. With a fixed average current rate, di/dt, the arc column shrinks in different situations. In both experiments, the arc diameter changes with three phases. At the beginning of forcing, the arc column seems stable. Consider that the thermal hysteresis plays an important role in it. Then, the arc shrinks with the current decline. Finally, the arc sharply decreases until the arc is quenched. Images of the arc dynamic characteristic are presented.

Simultaneous imaging of two-dimensional electron density and air-flow distribution over air-blast decaying arc

Sensitive Shack–Hartmann type laser wavefront sensors were applied to simultaneous imaging of two-dimensional electron density and air-flow distributions over decaying arc channels under air blasting with several pressures. Our experimental results showed that higher blasting pressures facilitated the rapid reduction of arc diameters and an increase in the electron densities around the gap centre due not only to the thermal pinch effect but also to air-flow disturbances, although there were no significant effects of the air blasting on the arc conductance.

A novel micro-controlled dynamic intramedullary nail for tibial middle fracture in Tibet mini-pigs

Objective To explore the effect on the fracture union in Tibet mini-pigs of a novel micro-controlled dynamic intramedullary nail which was self-designed on the basis of anatomic parameters of the animal tibia.Methods We measured the length,arc and inner diameters of the starting,narrowest and ending points of the bilateral tibial medullary cavities on the X-ray films of 20 Tibet mini-pigs.We designed and manufactured a new micro-controlled intramedullary nail using UG software on the basis of the anatomic measurements and CT 3D reconstructions of the animal tibia.The new fixation nails were tested in the animal models of left tibial middle fracture in 10 Tibet mini-pigs which were randomized into 2 groups (n =5).The experiment group was treated with the novel micro-controlled dynamic intramedullary nail and the control group with the static interlocking intramedullary nail.The fracture union was evaluated and compared between the 2 groups by X-ray,gait analysis and micro CT.Results Of the medullary cavity,the triangle proximal end was expansive,the middle segment was narrow and the oval distal end was also expansive in the Tibet mini-pigs.The length of medullary cavity averaged 113.31 ± 9.56 mm and the cavity arc 25.66° ± 3.37°.The nail length was 90 to 130 mm,the nail diameter 6 to 9 mm,the arc 15° to 25°,and the diameter of both locked screw and bioresorbable material 4.0 mm.The micro CT showed that the experimental group had significantly higher volume bone density (555.47 ± 23.49 mg/mm3) and bone volume fraction (0.84 + 0.04) than the control group (494.45 ± 16.62 mg/mm3 and 0.78 ± 0.03 respectively) (P ＜ 0.05).Conclusion It may help fracture union to design a novel micro-controlled dynamic intramedullary nail based on the theory of micro-controlled motion in clinic research. Key words: Bone nails; Fracture fixation, intramedully; Fracture healing; Imaging,three-dimensional

Galvanic Corrosion Behavior of Zinc/Steel Couple under Thin Electrolyte Layer

Galvanic corrosion exists widely in atmospheric environment. In this study, the most common used structure material - low carbon steel and its protective coating materials - zinc were chosen to form the galvanic couple, and coplanar zinc/steel galvanic corrosion behavior has been investigated by electrochemical methods and scanning electrochemical method under thin electrolyte layer (TEL), simulating the atmospheric corrosion environment. The results indicate that the corrosion resistance of steel and zinc is sensitive to the TEL thickness. The cathodic current density and the diameter of capacitive arc of steel increase and decrease respectively with the decreasing TEL thickness. When coupled together, galvanic current between zinc and steel is sensitive to the TEL thickness and cathode/anode area ratio. Steel can be well protected when coupled with zinc under present atmospheric corrosion environments.

A Study on Magnetism-Driven Gliding Arc Discharge

The diameter of non-thermal arc plasma is one of the main parameters that determine the current density of arc, so as to the temperature and the density of electrons. The imagines of gliding arc discharge driven by magnetism at atmosphere are captured observed and its dimension is measured by commercial CCD. The diameter projecting in the direction of motion of the arc (diameter in positive direction) is attained. And the relationship between diameter and current, magnetic field is analyzed, too.

Novel three-phase steam–air plasma torch for gasification of high-caloric waste

Research results are presented for an AC electric arc that burns a mixture of steam and air in a three-phase high-voltage plasma torch and can be implemented to produce plasma for plastic waste gasification. The dependences of electric parameters on the ratio of the steam to air mass flows (H2O/air ∼1–6) at an approximately constant total mass flow of the plasma-forming gas are obtained during several experiments. During the experiments, the arc parameters were as follows: voltage drop of 1.0–1.8kV, current of ∼28.5A and power of ∼52–86kW. The thermal efficiency of the plasma torch was ∼94–95%. CCD cameras operating at 4000fps were used to determine the average discharge length of ∼798mm. Photography with a high shutter speed (1/8000s) was used to determine the average arc diameter (∼4.47mm). Arc temperatures were calculated (10,000–11,500K) using the thermodynamic equilibrium approach. Experimental results indicate that increases in the steam content of the steam–air plasma lead to a reduction of the arc’s temperature and electrical conductivity. Using an equilibrium approach, the main parameters of plasma gasification were estimated: syngas yield (3.62–3.48m3/kg), composition (H2 – 55.5–62.5, CO – 32.8–34.1vol.%) and energy consumption (11.0–12.3MJ/kg).

Characterizing Local O2 Diffusive Losses in GDLs of PEFCs Using Simplified Flow Field Patterns (“2D”,“1D”,“0D”)

By means of advanced diagnostic tools – neutron imaging, pulsed gas method (helox or O2 pulses during air operation) and electrochemical impedance spectroscopy (EIS) – three different flow fields are characterized in a differential (small-size cell operated at high stoichiometry) Polymer Electrolyte Fuel Cell (PEFC) to emulate the local behavior of a full-size cell. The channel-rib structures are designed so as to obtain 2D, 1D and 0D gradients of O2 concentration across the gas diffusion layer (GDL). The important bulk-diffusion losses (evaluated with pulsed helox) of the “2D” cell compared to the “1D” cell indicate the effect of lateral oxygen diffusion in the GDL. Non-bulk diffusion losses (Knudsen and/or thin film diffusion, evaluated with pulsed O2) also play a non-negligible role on the overall diffusive losses. In particular, their increase in dry conditions for the “1D” and the “0D” cells might be a consequence of drying effects in the electrode.EIS spectra can be interpreted consistently with the results of the pulsed gas method: the increase of arc diameter can be correlated with the overall mass transport losses including both bulk and non-bulk diffusion losses.