Strip Plane Research Articles

Magnetic relaxation in an anisotropic superconducting strip

We theoretically study the magnetic relaxation in a thin anisotropic superconducting strip placed in an external magnetic field ${H}_{a}$ perpendicular to its plane. Both the critical current density ${j}_{c}$ and the effective depth of the pinning wells, ${U}_{0}$, are assumed to depend on the angle $\ensuremath{\theta}$ between the local direction of the magnetic induction in the strip and the normal to the strip plane. Exact expressions for the magnetic relaxation are found for a simple model describing the anisotropy of layered superconductors. It is shown that the ${H}_{a}$ dependence of the magnetic relaxation rate in the anisotropic case qualitatively differs from the appropriate dependence in the isotropic strip.

Superconducting strip in an oblique magnetic field

As an example for a seemingly simple but actually intricate problem, we study the Bean critical state in a superconducting strip of finite thickness $d$ and width $2w⪢d$ placed in an oblique magnetic field. The analytical solution is obtained to leading order in the small parameter $d∕w$. The critical state depends on how the applied magnetic field is switched on, e.g., at a constant tilt angle, or first the perpendicular and then the parallel field component. For these two basic scenarios we obtain the distributions of current density and magnetic field in the critical states. In particular, we find the shapes of the flux-free core and of the lines separating regions with opposite direction of the critical currents, the detailed magnetic field lines (along the vortex lines), and both components of the magnetic moment. The component of the magnetic moment parallel to the strip plane is a nonmonotonic function of the applied magnetic field.

Left handed coplanar waveguide band pass filters based on bi-layer split ring resonators

A new type of compact band pass filters based on planar structures with three metal levels is proposed. The central layer consists on a coplanar waveguide (CPW) with periodic wire connections between the central strip and ground planes. In the upper and lower metal levels, split ring resonators (SRRs) are etched and aligned with the slots. The wires make the structure to behave as a microwave plasma, with a negative effective permittivity covering a wide frequency range. SRRs, which are magnetically coupled to the CPW, provide a negative magnetic permeability in a narrow frequency range above their resonant frequency. The result is a band pass structure which supports wave propagation in a frequency interval where negative permittivity and permeability coexist. The bandwidth of the structure can be controlled by tuning the resonant frequency of the upper and lower SRRs and the distance between SRRs. Fabricated prototype devices exhibit very low insertion losses in the pass band (<1.5 dB) and high frequency selectivity.

Characterisation of an inhomogeneously irradiated microstrip detector using a fine spot infrared laser

A prototype silicon microstrip detector with p-strip read-out on oxygen enriched n-type substrate has been non-homogeneously irradiated using a 24 GeV/ c proton beam at the CERN-PS accelerator. The detector has a semicircular shape with radial strip geometry. The peak fluence received by the detector was 4.6×10 14 p/cm 2 though the non-uniform nature of the exposure left part of the detector unirradiated. The inhomogeneous irradiation introduced a damage profile in the detector approximating to that expected in the inner LHC region. High-irradiation gradients are important to study as they can modify the electric field within the silicon. Of special interest are changes in the component of the electric field parallel to the strip plane but perpendicular to the strips, which could lead to systematic shifts in the reconstructed cluster position. If these (flux and position dependent) shifts are sufficiently large they could contribute to degrading the spatial resolution of the detector. In order to quantify these effects, a precision narrow focus light spot from an infrared laser was used to investigate the charge collection properties of the sensor. Particular attention was devoted to the regions where a high gradient of the fluence will have introduced a large gradient in the effective local space charge. The results reported below place limits on the ‘distortions’ due to non-uniform irradiation.

New CPW low‐pass filter based on a slow wave structure

AbstractA new periodic loaded coplanar waveguide (CPW) low‐pass filter with very sharp cutoff has been designed and fabricated. The device consists of a CPW structure with T‐shaped periodic patterns on both the central strip and ground planes. With such a design, capacitive coupling is added between the signal strip and ground planes at periodic positions, resulting in a filtering action and slow‐wave effect. In addition to a sharp cutoff, the device exhibits very low insertion loss in the pass band, wide rejection bandwidth, and simple design and fabrication. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 38: 190–193, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11011

Bimaterial curvature measurements for the CTE of adhesives: optimization, modeling, and stability

Quantification of the coefficient of thermal expansion (CTE), the stress-free temperature, and the residual stress state is of critical importance for many applications involving bonded systems such as coatings, adhesives, and other laminated systems. This paper revisits Timoshenko's solution for the curvature of a bimaterial strip (plane stress) by identifying optimal configurations which improve the sensitivity and minimize the effects of time-dependent changes in moduli. We find that when the material system is optimized, the curvature calculation is virtually insensitive to the modulus change. A similar solution is developed from classical lamination theory (CLT) for plate-like geometries in the case of cylindrical bending. These two solutions—Timoshenko's beam solution and the cylindrical bending solution based on CLT—turn out to be the two asymptotes in the predicted curvatures, using the principle of energy minimization as shown in the numerical analysis. For thin layer systems, the bimaterial system is much more sensitive than the bulk material system in curvature measurements. This technique can be easily implemented in modern thermal mechanical analysis equipment, which is readily available in most polymer laboratories.

New periodic-loaded electromagnetic bandgap coplanar waveguide with complete spurious passband suppression

In this work, coplanar waveguides (CPW) periodically loaded with shunt capacitances and periodically perturbed by varying the distance between the central strip (of constant width) and ground planes are studied. It is demonstrated that the multiple spurious passbands above the Bragg frequency, inherent to the presence of the reactive elements, can be completely and efficiently rejected by means of very simple geometry perturbation. This result is in contrast to previous works, where the rejection of multiple frequencies requires complex layout patterns and reveals that the elimination of spurious frequency bands in periodic loaded CPWs cannot be merely estimated from the Fourier transform of the perturbation geometry.

Magnetostrictive properties of cube-textured Si steel sheets by oxide-separator-induced decarburization

Magnetostrictive properties of cube textured 2.9%Si-0.7%Mn steel strips by oxide-separator-induced decarburization have been investigated. The strip consisting of cube-oriented grains of about 0.3 mm in diameter exhibited a small ac magnetostriction of the order of 10/sup -6/ virtually in any direction in the strip plane without external stresses. In the easy directions, the magnetostriction at 1.5 T of magnetic induction was about 1.5 /spl times/ 10/sup -6/, and it decreased to a smaller positive value by the application of external tensile stresses. In the directions of 25/spl deg/ and 45/spl deg/ to the easy directions, negative (about -2 /spl times/ 10/sup -6/) and positive (2 /spl times/ 10/sup -6/) magnetostrictions were observed, respectively. The amount of transverse domain structure in the demagnetized state when alternately magnetized in the easy directions was estimated to be about 18% in volume fraction.

Propagation characteristics of superconducting microstrip lines

The modified spectral-domain approach is applied to study the propagation characteristics of high temperature superconducting microstrip lines whose signal strip and ground plane are of arbitrary thickness. In this study, numerical results for effective dielectric constant, attenuation constant, and strip current distribution are presented to discuss the effects due to frequency, temperature, strip thickness, and substrate loss tangent. In particular, the conductor and dielectric attenuation constants of superconducting microstrip line are depicted separately to discuss the mechanism of the line losses. A comparison with published theoretical and experimental results is also included to check the accuracy of the new approach's results.

Effect of contact recombination on the transverse conductivity distribution in photoexcited semiconductor coplanar waveguides

A modified 1-D approximation for the 2-D diffusion-controlled distribution of photoconductivity in the cross-sectional region of illuminated semiconductor coplanar waveguides (CPW) is presented, taking into account contact recombination at the strip and ground plane metallisation.

Transient propagation in lossy coplanar waveguides

Propagation of picosecond Gaussian and rectangular pulses along a lossy coplanar waveguide is investigated in detail. To this end, a new empirical formula for attenuation constant is proposed for discussing the conductor and leakage losses associated with the coplanar waveguide in which the thickness and conductivity of signal strip and ground planes are finite. This formula is obtained by comparing the results by the modified spectral-domain approach with those by the previous empirical formulas. Based on this new empirical formula, an efficient time-domain propagation model is established and applied to analyze the transient characteristics of Gaussian and rectangular pulses propagated along a lossy coplanar waveguide. In particular, the transient propagated pulses calculated by different empirical formulas are discussed and compared with those of the experimental data.

Dispersion and attenuation characteristics of coplanar waveguides with finite metallization thickness and conductivity

A new approach of modifying the conventional spectral-domain approach is proposed for an analysis of the coplanar waveguide whose signal strip and ground planes have finite thickness and conductivity. By introducing suitable equivalent sources in the slot and signal strip regions, the problem can be significantly simplified by reducing the two-dimensional numerical integration into the one-dimensional one, thus it can be treated as easily as the conventional spectral-domain approach. By this modified approach, both the phase constant and attenuation constant can be determined simultaneously without using the assumption that the metallization thickness is much larger or smaller than the skin depth. In this work, comparison with published theoretical and experimental results is presented to check the accuracy of the new approach's results. In particular, the effective dielectric constant /spl epsiv//sub eff/ and attenuation constant a of a coplanar waveguide with finite metallization thickness and finite conductivity are discussed in detail, together with the current distributions along the signal strip and ground planes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Modified spectral-domain approach for microstrip lines with finite metallisation thickness and conductivity

A modified spectral-domain approach is proposed for an analysis of the microstrip line whose signal strip and ground plane have finite thickness and conductivity. To improve the accuracy of the results, all three components of the strip current which have three-dimensional dependence are included in the analysis. With the basis functions properly chosen, this new approach can be treated as easily as the conventional spectral-domain approach. By this modified approach, both the phase constant and attenuation constant can be determined simultaneously without using the assumption that the skin depth is much larger or smaller than the signal strip thickness. In this work, comparison with published theoretical and experimental results is presented to check the accuracy of the new approach. In particular, the effective dielectric constant and attenuation constant of a microstrip line with finite metallisation thickness and finite conductivity are discussed in detail, together with the longitudinal current distributions along the signal strip.

Study of inclined particle tracks in micro strip gas counters

The response of micro strip gas counters (MSGC) has been studied for particle tracks with inclined incidence with respect to the strip plane. The setup consisted of four 10 × 10 cm 2 MSGC detectors arranged in a cosmic ray hodoscope with a trigger threshold of 300 MeV/ c for muons. Results are given for the collected charge, the spatial resolution and the detection efficiencies. A Monte Carlo simulation has been used to understand the effects of cross talk in the data and to extrapolate the data to other angles of incidence.

Influence of the chemical etching on magnetic and electric properties of Co-rich amorphous sheets

The anisotropy characteristics of amorphous strips cut out from a Metglas 2714A ribbon and uniformly thinned by chemical etching are considered. Magnetic and electric properties are measured in the direction of the original ribbon axis and perpendicular to it, in the strip plane. Thinned samples are analyzed also after annealing above the Curie temperature, where annealing in the absence of an applied magnetic field and external stress gives rise to an unusual change in the easy axis direction. The results show that the defects mostly responsible for the anisotropy are prevailingly concentrated near the wheel-side and the air-side of the ribbon with different distributions on the two surfaces.

Changes of the anisotropy direction in amorphous strips due to annealing in absence of magnetic field and external stresses

An unusual change of the anisotropy direction is observed on square strips of Co-based amorphous alloy of Metglas 2714A. This change is obtained by annealing without any applied magnetic field or external stress. The anisotropy direction moves from its original direction along the ribbon axis to the transverse direction in the strip plane. This occurs when annealing is performed above the Curie temperature. The effect is analysed through the characteristics of hysteresis loops together with measurements of complex permeability and magnetoresistivity and is discussed on the basis of the magnetoelastic behavior of the material and the different structural morphologies of the surface layers of the ribbons.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

A prototype kinetic inductance thermometer for X-ray calorimetry

We have measured the parameters of a prototype kinetic inductance thermometer for X-ray calorimetry which was fabricated at GSFC. This device consists of an aluminum meander strip and ground plane and operates at about 1.2 K. For thermal isolation, the device was suspended on Kevlar threads along with a heater and a germanium resistance thermometer. The meander strip was included in the tank circuit of a 10 MHz tunnel diode oscillator operating at about 1 K. The kinetic inductance was measured by monitoring the oscillator frequency. The temperature dependence of the kinetic inductance was found to be in reasonable agreement with the behavior predicted from the device parameters. Having characterized this proof-of-concept device, we intend to investigate the suitability of kinetic inductors operating at lower temperatures for X-ray calorimetry.

A beam intensity profile monitor based on secondary electron emission

Two dual function intensity profile monitors have been designed for a measurement of parity violation in p -p scattering at about 230 MeV using longitudinally polarized protons. Each device contains a set of split secondary electron emission (SEM) foils to determine the median of the beam current distribution (in x and y). The split foils, coupled through servoamplifiers and operational amplifiers to upstream aircore steering magnets, have demonstrated the ability to hold the beam position stable to ±5 μm for beam position fluctuations up to 1000 Hz. These monitors also contain a set of foil strip planes giving information on the intensity distribution projected onto the two orthogonal axes, x and y. Data were acquired using 0.008 mm thick, 0.90 mm wide aluminum foil strips at 1.00 mm centers. The foil strip planes were able to determine the beam centroid to within ±3 μm after one hour of data taking with a 100 nA, 15 mm FWHM Gaussian beam.

Incremental diffraction coefficients for planar surfaces

Exact expressions for incremental diffraction coefficients at arbitrary angles of incidence and scattering are derived directly in terms of the corresponding two-dimensional, cylindrical diffraction coefficients. The derivation is limited to perfectly conducting scatterers that consist of planar surfaces, such as the wedge, the slit in an infinite plane, the strip, parallel or skewed planes, polygonal cylinders, or any combination thereof; and requires a known expression (whether exact or approximate) for the two-dimensional diffraction coefficients produced by the current on each different plane. Specifically, if one can supply an expression for the conventional diffraction coefficients of a two-dimensional planar scatterer, one can immediately find the incremental diffraction coefficients through direct substitution. No integration, differentiation, or specific knowledge of the current is required. Special attention is given to defining ambiguously all real angles and their analytic continuation into imaginary values required by the incremental diffraction coefficients. >

Compartmentalization of water in human atherosclerotic lesions. Changes in distribution and exclusion volumes for plasma macromolecules.

High concentrations of LDL and other plasma macromolecules are present in normal aortic intima and early proliferative atherosclerotic lesions that have not yet accumulated lipid. Their compartmentalization within the tissue water was estimated from the concentrations of low density lipoprotein (LDL), alpha 2-macroglobulin (alpha 2-M), and albumin in interstitial fluid and adjacent intimal tissue. Interstitial fluid was collected on filter paper inserted into natural strip planes in the intima; macromolecules in interstitial fluid and tissue were assayed by rocket immunoelectrophoresis directly from the papers or tissue. From their concentrations in interstitial fluid and total tissue water, the fractional and absolute volumes in which they were distributed (distribution volume) or from which they were excluded (exclusion volume) were calculated for each macromolecule. Compared with normal intima, the distribution volume increased by 60% and the exclusion volume by 95% in early gelatinous lesions; exclusion volume fraction was linearly related to molecular mass. In more advanced lesions, there was disproportionate exclusion of LDL and alpha 2-M. Their distribution volumes decreased and their concentrations in interstitial fluid increased; the concentration showed a significant inverse relation with distribution volume (regression coefficient, b = -0.53, p less than 0.01). Redistribution of tissue water may concentrate LDL in interstitial fluid, and contribute to its extracellular deposition.