Circular Conductor Research Articles

Exact Space-Charge Field Solutions for Cylindrically Symmetric Beam Currents in a Circular Conductor Pipe

We derive an exact formalism for calculating the space-charge fields of an electron beam inside of a perfectly conducting cylindrical pipe. The formalism utilizes a series expansion of the beam-charge and current densities in Bessel functions in conjunction with a time-dependent Green's function method to compute the exact space-charge fields due to the beam with the appropriate conductor boundary conditions. The formalism can be utilized for theoretical and numerical studies of high-space-charge beams, such as those found in high-power microwave sources. As a numerical example, we demonstrate how this formalism can be implemented numerically to compute the space-charge fields for a bunched beam which is undergoing radial oscillations.

Formation of a Double Circular Erosion Pattern on SiO2 Dielectric Target and Its Effect to Utilization Rate in RF Magnetron Sputtering

A circular erosion pattern is formed on the surface of a circular metal conductor target with permanent magnets on its back in rf magnetron sputtering. In this case, the theory behind the erosion pattern has been established. On the other hand, in the case of a dielectric target, a double circular erosion pattern is formed. This pattern is widely known qualitatively and experimentally; however, it has not yet been studied theoretically. In this study, we performed a magnetron sputtering experiment with a SiO2 dielectric target, and were able to confirm the formation of a double circular erosion pattern, which agrees with qualitative theory. Moreover, insulation resistance varied with the thickness of the SiO2 target; thus the dimensions of the double circular erosion pattern varied. Furthermore, we confirmed that a double circular erosion pattern changed by making a gap between the SiO2 target and guard ring. We discussed about utilization rate of the target.

Multiphase transport processes of droplet impact and ice accretion on surfaces

In this paper, transport phenomena are examined for multiphase heat transfer with incoming supercooled droplets and icing of heated curved surfaces. The processes of rime ice, transition and combined rime/glaze ice conditions are investigated. Heat conduction equations in the ice and unfrozen water layers are solved simultaneously with the mass balance. Energy input from the heated boundary (due to electrical heat generation) affects the growth of the glaze film thickness and associated liquid runback along the ice surface. Validation of the predictive model is carried out through comparisons with experimental data involving ice buildup on heated, non-rotating circular conductors. Close agreement is achieved between the predicted ice growth and the measured data. Physical effects of cable radius, surface heating rate and surface curvature are presented. The heat transfer model approaches the dry growth limit, based on mass conservation alone, under appropriate thermal conditions when the surface heating rate is diminished sufficiently. By examining all of the relevant physical processes leading to ice accretion on the surface, a single formulation is developed to cover the entire range of rime, transition and combined rime/glaze ice conditions, including the simultaneous growth of unfrozen water and ice layers.

Double circular erosion patterns on dielectric target in magnetron sputtering

In rf magnetron sputtering, a circular erosion pattern forms on the surface of a circular metal conductor target with permanent magnets on its back. In this case, the theory behind the erosion pattern has been established. However, in the case of a dielectric target, a double circular erosion pattern is formed. So far, this pattern has been phenomenologically recognized by experimenters; however, it has not yet been investigated. In this study, we performed a magnetron sputtering experiment with a SiO2 dielectric target, and confirmed the formation of a double circular erosion pattern. The dimensions of the double circular erosion pattern varied depending on the insulation resistance or the thickness of the SiO2 target. Furthermore, we found that the dimensions of a double circular erosion pattern changed by making a gap between the SiO2 target and guard ring. Based on the experimental results, we have proposed a qualitative model to explain the formation mechanism of double circular erosion patterns.

Flux linkage areas of coupling current loops for different shape cable-in-conduit conductor

For large scale application such as fusion magnets, the cable-in-conduit conductor (CICC) is the most promising conductor because of its high mechanical strength under large electromagnetic force. However, there are still remained issues about degradation of critical current of Nb 3Sn conductor and unpredictable AC loss. With regard to the second item, inter-strand coupling current loss is dominant among the AC losses and unpredictable before fabricating large scale conductor. The strand displacements which are caused by the compaction of the conductor in order to increase its current density would cause the loss. In order to do quantitative investigation of the relation between the loss and the strand displacements, we measured strand traces for circular conductor and rectangular conductor. The evaluation of the flux linkage areas which are driving forces of the coupling current indicated that the flux linkage areas have strong dependence on the changing magnetic field only for the rectangular one. It also indicated that the loss should be large when the field is applied from the direction which is perpendicular to the wide surface of the conduit.

Nonreciprocity in circular magnetoplasma-filled waveguides above the cyclotron frequency

The electromagnetic behavior of a circular perfect electric conductor waveguide with various magnetoplasma filling configurations has been investigated near the cyclotron resonance region at 77 K with longitudinal magnetic bias. Faraday rotation in the forward and reverse directions along with the waveguide geometry effect provided the nonreciprocal attenuation to design an isolator for frequencies up to the terahertz region. Based on the finite element method, two-dimensional eigenvalue as well as three-dimensional numerical simulations are provided to illustrate the phenomena. Unprecedented performance was attained for the coaxial configuration in terms of the bias-to-frequency ratio. Other configurations were found to have some nonreciprocity as well.

Computer‐aided modeling of circular conductors

AbstractCircular conductors have manufacturing advantage compared with rectangular conductors in building microwave components such as filters and couplers which make it very popular for microwave designers. The accurate and efficient evaluation results of the capacitance, inductance, and characteristic impedance of circular conductors can help the designers to optimize the layout of the integrated circuits. In this article, we use the finite element method to compute the capacitance per unit length, inductance per unit length, and characteristic impedance of circular conductors. Mainly, we focus our computation and modeling on four types of systems as follows: a single circular wire above ground plane in a dielectric layer, a single circular conductor above a ground plane in a lossy dielectric layer, parallel coupled slab lines with homogenous dielectric layer, and three circular rod arrays in a rectangular trough with homogenous dielectric layer. Comparisons with published results demonstrate excellent agreement with the modeling. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1366–1372, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24307

Status of the ITER magnets

The first 2 years of the ITER IO has seen substantial progress towards the construction of the magnets, in three main areas. Firstly, the design has been developed under the conflicting constraints to minimise construction costs and to maximise plasma physics performance. Building construction momentum while updating the design to take account of new physics assessments of the coil requirements has been challenging. Secondly, with a stabilising design, it has been possible for the Domestic Agencies to launch the first industrial procurement contracts. And thirdly, critical R&D to confirm the performance of the Nb3Sn cable in conduit design is proceeding successfully. The design consolidation has been accompanied by design reviews involving the international community. The reviews conducted by magnet experts have enabled a consensus to be built on choosing between some of the design options in the original ITER basic design in 2001. The major design decisions were to maintain the circular Nb 3Sn conductor embedded in radial plates for the toroidal field (TF) coils and to maintain NbTi-based conductors for the PF coils. Cold testing, at low current, is also being introduced for quality control purposes for all coils.

RADIATION FROM AN ECCENTRIC COATED CYLINDER WITH SLOTS OF ARBITRARY SIZES AND POSITIONS

The transverse electric (TE) field patterns and characteris- tics are considered for a cylinder with N infinite axialslots of arbitrary opening size and position. The cylinder is a thin circular conductor and covered by an eccentric material. Radiations are determined by applying the boundary conditions to the cylindrical wave functions of the fields. The addition theorem of Bessel functions is employed to find an infinite-series solution in Fourier-Bessel series form. Results are achieved by reducing the produced infinite series to a finite num- ber of terms and judged against other published data. Numerical and graphical results for different values are also presented and discussed for small eccentricities.

Plasma Acceleration and Heating Using Hybrid Magnetic Fields

The repulsive force between two wires with large currents flowing in opposite directions through the wires can be used to propel a light circular conductor located above a massive ring. Then the axial velocity can reach 500 km/s and an auxiliary constant magnetic field controls the radial velocity. This allows to get a high concentration of energy at any distance from the laboratory equipment. A further application could be the investigation of the equation of state of matter at high densities and the triggering of fusion reactions.

A Design of ITER TF Coils With Rectangular Conductor

In the ITER TF Coils reference design the circular conductor is enclosed in the grooves of a stainless steel plate, the so called radial plate. In this paper, we present an alternative solution using a relatively thin walled rectangular conductor without an additional reinforcing structure. We describe the conductor and the layout of the winding pack and analyze the magnetic, thermo-hy-draulic and mechanical behavior of the proposed coil. Then a cost analysis is carried out to estimate the significant saving that can be achieved by the proposed solution.

On the stress-strain state of film structures in space at electrodynamic deployment

We discuss a possibility of using the Ampere force for deployment and stabilization of film structures in space. It is supposed that a conductor connected with a power supply is deposited on the surface of a thin film, or solar batteries are used as conductors with current. The stress and strain of the thin film, caused by the electric current flow over a circular conductor confining this film, are found. The method of calculating the radial component of the stress tensor in a film, connected with concentric circular conductors with current, is obtained. The distribution of stresses for a film with three conductors is calculated. A possibility of minimizing the magnetic moment of a system of currents is discussed.

Analysis of a shielded transmission line containing circular cylindrical conductors and coplanar lines on a grounded shield

For the first time, a method is proposed for numerical calculation of a monolithic multiconductor shielded transmission line integrated with planar coupling circuits. Formulas for the matrix of the per-unit-length capacitance of coupled conductors are derived. The electric parameters of fundamental modes are calculated in the quasi-static approximation. The computation results can be used for designing monoblock microwave filters.

Accurate closed-form formulas for the electromagnetic parameters of squared coaxial lines

This article presents a set of accurate closed-form formulas for the electromagnetic parameters (inductance ( L ), capacitance ( C ) and characteristic impedance ( Z c )) for squared coaxial lines with circular and square inner conductor. The analytical expressions, deduced from rigorous analysis by the finite element method (FEM), method of moments (MoM) and curves fitting techniques, can be easily implemented in CAD simulation tools, to design components for wireless communication. This study presents accurate and suitable general expressions for all squared coaxial lines with a wide range of outer to inner conductors ratio between 1.2 and 10. As an application, we present the design of 60 GHz branch line couplers.

A new shielding effectiveness measurement method based on a skin-effect transmission line coupler

Abstract. We propose a new convenient material shielding effectiveness measurement method based on a skin-effect transmission line coupler. The method is somewhat similar to the arrangement with two coupled TEM cells known from literature. The transmission line coupler consists of a pair of identical transmission line 2-port devices. Each device contains a coaxial waveguide, with a circular inner conductor and an outer conductor having a square cross section. One side of the outer conductor is left completely open as a slot. The slot is surrounded by a large metal housing to contact the two halves. As a measure for the shielding effectiveness the coupling between the two devices is measured in terms of scattering parameters after the test material is brought between the two halves. The devices can be used in a range from low frequencies to a few GHz.

Dangerous Voltages due to Direct Lightning Strike into the Communication Tower

This paper presents a novel technique for computing dangerous voltages due to direct lightning strike into the communication tower and associated earthing system, which is based on the use of the well-known ATP-EMTP software package. The earthing grid and the communication tower structure are approximated by the circular cross section conductors. In numerical model, conductors are subdivided into segments (1D finite elements) and Clark's model with distributed constant parameters is then applied. Because of the limitations of ATP-EMTP software package, the leakage resistance of buried segments is modelled as additional lumped parameter. Analytical expressions for distributed and lumped segment parameters are derived using the average potential method. Mutual electromagnetic coupling between segments is neglected due to the limitations imposed by the ATP-EMTP software package, which is based on transmission line approach. Separate computer program is developed for obtaining the earth surface transient potential distribution, from which step and touch voltages are then computed.

A novel method for the collimation of ions at atmospheric pressure

Measured gains in source-to-target ion transmission of well over two orders of magnitude are reported from the application of a robust and versatile electrostatic lens that requires no voltage supply and consumes negligible power. When exposed to an ion flux across a potential gradient, a series of electrically-floating circular conductors automatically attain a profile of convergent potentials. This passive ion lens is used to collimate atmospheric ion source currents that range from 30 pA to 7 nA, increasing the ion signal strength at the target by factors of 20–130 times that of the unaided signal.

Line Segment Pole Functions in the MMP Method Applied to Shielded Cables

The multiple multipole method (MMP) of computation for electromagnetic field problems that has been proposed as an alternative to existing finite-element and related methods is being extended in this work by the use of segment functions. In this method linear combinations of defining functions that satisfy themselves the pertaining partial differential equations (e.g., Laplace's equation) are employed to synthesize a solution of a potential in a certain region with given boundary conditions. The solution, as given by these defining functions, will be matched at selected points on the boundary (e.g., conductor surface). This will generate a redundant set of equations from which the coefficients of the various functions in the series solutions are deduced by the method of least squares. To reduce the number of functions in the series expansion, a novel class of harmonic functions obtained by integration of monopole or dipole point functions is investigated. These functions are obtained by integrating a point source function along a line segment. The efficiency of the procedure using these functions has been demonstrated in the calculation of the electrostatic potential and the capacitance of practical two-core cables with elliptical and circular conductors and three-core cables with sector shaped conductors

Calculation of transverse waves in a shielded transmission line containing circular cylindrical conductors

A method is proposed for calculating a shielded homogeneous multiconductor transmission line containing conductors of circular cross section. Formulas are obtained for the matrix of the conductor capacitance per unit length and the electric parameters of transverse electromagnetic waves.

Design and Qualification of ITER CS and TF Cooling Inlets

In the ITER superconducting magnets, the CIC conductors cooling is insured by supercritical helium forced flow in the central and annular parallel channels. In the Central Solenoid, with a thick square jacket conductor, the helium inlet is in the highest field region at the inner bore pancake joggle, and it has to support the high hoop force stress level with a very low stress concentration factor. In the TF magnets, a thin jacket circular conductor is wound in double pancakes, inserted into radial plates, stacked and embedded into a steel case. The helium inlets are located at the inner bore, in the limited space between the radial plates and the coil casing. The PF coils helium inlets, not studied here, are similar to the CS ones, but with a lower stress level. A complete qualification work on the CS and TF helium inlets is presented. A design optimization was performed, by FEM analysis, resulting in acceptable stress level for both helium inlets. The welding procedure was qualified and specific fatigue life mock-ups were designed, analyzed and manufactured using representative jacket materials. Fatigue life qualification at 4 K was performed in the FZK test facility applying the relevant loading and number of cycles. Hydraulic mock-ups were manufactured and qualified in the CEA test facility using GN2 at relevant Reynolds number. Pressure drop as well as flow repartition inside the conductors' petals were measured. The mechanical and hydraulic results are presented