Showing papers on "Shields published in 2003"

Particulate reduction using temperature-controlled chamber shield

Abstract: Particle flaking is reduced in a semiconductor wafer processing apparatus by installing a chamber shield assembly in the chamber of the apparatus. The shield assembly includes a plurality of nested shields that are supported out of contact with each other and suspended such that, during thermal expansion and contraction, gaps are maintained that are sufficient to avoid arcing. Alignment structure on the shields and on the chamber walls force the shields to align concentrically and maintain the gaps. The shields are made of aluminum or another thermally conductive material and have cross-sectional areas large enough to provide high thermal conductivity throughout the shields. Mounting flanges and other mounting surfaces are provided on the shields that form intimate thermal contact with sufficient contacting area to insure high thermal conductivity from the shields to the temperature controlled walls of the chamber. Radiant lamps of an array are spaced around the chamber and extend vertically to expose multiple shields across large areas to heat for pre-heating bake-out of the shields and to eliminate thermal shock upon processing the first wafer of a run.

Fully shielded perpendicular recording writer

Abstract: Conventional perpendicular writers that utilize an extended return pole are subject to large flux leakage. This problem has been reduced in the prior art by adding a downstream shield. This still leaves significant upstream leakage. This has now been eliminated by adding an upstream shield and then connecting the up and downstream shields by means of side shields. The latter need not extend all the way from the downstream to the upstream shield in which case their thickness is increased relative to the full side shields.

Integral methods for analysis and design of low-frequency conductive shields

Abstract: This paper presents and compares two different approaches to the analysis and design of nonferrous shields for extremely low-frequency magnetic fields. The first method is based on a circuital approach where the shield is modeled by a set of conductors coupled with each other by a matrix of self and mutual inductances. The second technique is based on an algebraic formulation of electromagnetic fields and adapted by means of integral equations to the analysis of thin conductive sheets. The paper shows the accuracy of the two methods for calculating induced current density inside the shield and for evaluating magnetic flux density in the shielded region.

Optimum passive shields for mitigation of power lines magnetic field

Abstract: This paper presents a systematic semi-heuristic method to locate the most effective passive shield with the aim of mitigating the magnetic field generated from overhead power lines, at both sides from the line. As an example, the method is applied to two different phase arrangements used frequently in EHV: flat and double-circuit vertical, with shields of a single loop (two conductors), two loops with a common conductor (three conductors), or two separate loops (four conductors). Numerical results of mitigation, obtained with different solutions and further discussion, are also provided.

Evaluation of Shear Compliant Borders for Wrinkle Reduction in Thin Film Membrane Structures

Abstract: Many ultra-lightweight (Gossamer) space structure designs under consideration for future missions (e.g. solar sails, sun shields, reflectors) are comprised of thin film, flat membrane panels. Such structures must be maintained in a state of biaxial tension in order to suppress wrinkle formation. One such support method under consideration involves the incorporation of integrated, shear compliant borders along the top and bottom edges of the membrane. In this paper, finite element modeling is used to predict the effectiveness of various shear-compliant support geometries. The wrinkle configurations predicted (e.g. amplitude, angle) compare favorably with experimental surface measurements, made using photogrammetry, of membranes incorporating shear compliant borders.

Optimizing active and passive magnetic shields in induction heating by a genetic algorithm

Abstract: This paper presents a method for designing optimal passive and active shields for axisymmetric induction heaters. Such shields are needed to protect human operators and external electronic equipment from stray magnetic fields. The method uses a genetic algorithm (GA) to minimize an objective function. This function reduces the magnetic field in the target area, the power dissipation in the active and passive shields, and the influence of the shields on the heating process. The GA returns the position and height of the passive shield, the optimal current for the active shield, and the number of turns of all coils. The paper describes two optimization modes: 1) optimization of only the active shield with fixed passive shield and 2) global optimization of both active and passive shields. Several passive shields are studied: electrically conductive shields and both electrically and magnetically conductive shields. The field reduction depends on the optimization mode and the passive shield properties, but always exceeds 25 dB for combined active and passive shields. Finally, the paper compares the results of the simulations to experimental measurements.

Magnetic random access memory designs with patterned and stabilized magnetic shields

Abstract: A magnetic tunneling junction (MTJ) memory cell and an MRAM array of such cells, is shielded by magnetic shields of ferromagnetic material or by ferromagnetic shields that are stabilized by patterned layers of antiferromagnetic material or permanent magnetic material. The ferromagnetic portions of the shields surround the MTJ cells substantially conformally and thereby can compensate the poles of the free layers of MTJ cells of various geometric cross-sectional shapes and also protect the cells from the adverse effects of extraneous fields. The additional antiferromagnetic and permanent magnetic materials stabilize the shields by exchange or direct coupling.

Shielding techniques of the low-frequency magnetic field from cable power lines

Abstract: The influence of the geometrical configuration of three single-core cable lines on the generated magnetic field is evaluated in the preliminary analysis. Numerical and experimental procedures are applied to estimate the performances of open or closed shields made of conductive or magnetic materials. A new high-voltage single-core "green cable" is proposed, in which the aluminum conductor is coiled by a double-layer shield realized with copper wires and a ferromagnetic sheath.

A method for depositing multilayer coatings

Abstract: The invention relates to a method and apparatus for the generation of multilayered coatings onto substrates. Typically the apparatus used is a closed field unbalanced magnetron configuration in conjunction with one or more cylindrical and rotatable shields and a substrate carrier on which the substrates to be coated are carried. The shields and substrate holder are provided for rotation about a common axis of rotation. The shields are provided with apertures to allow the selective positioning of the apertures to define a passage or passages along which material from the targets can pass onto the substrates. The targets can be cleaned prior to the coating stage by operation of the targets with the shields selectively positioned to prevent the deposited material from reaching the substrates.

Hypervelocity Impacts on Thin Metallic and Composite Space Debris Bumper Shields

Abstract: The mechanism of hypervelocity impact crater formation in metallic and composite space debris shields has been investigated. Both normal and oblique impact crater formations have been investigated using 2.2-mm-thick aluminum (At 2017), carbon fiber reinforced plastic (CFRP) and aramid fiber reinforced plastic (AFRP) space debris shields in a two-stage light gas gun. A cylindrical projectile made of high-density polyethylene (14 mm in diameter and length) at a muzzle speed of 5.0 +/- 0.2 km/s is used to create the craters in the debris bumper shields. The microscopic study reveals the formation of adiabatic shear bands near the crater zone, from where the secondary cracks emerge, ultimately resulting in the formation of the craters in thin aluminium plates at impact angles of 90, 51, and 64 deg. On the other hand, surface delamination zones caused by the peeling of surface piles surrounding the impact and exit craters are observed in the case of CFRP and AFRP debris shields at normal impact. To estimate the temperature near the craters, time-integrated spectrum of the light emission during the crater formation is recorded. The measurements are taken in the near-UV region of the spectrum. Based on the CN emission from the projectile material, the temperature of the debris cloud during normal and oblique impacts at 5 km/s are estimated to be between 7300 +/- 300 and 7600 +/- 300 K, respectively.

Cross-track shielding in a GMR head

Abstract: A magnetoresistive read/write head includes an integral top and side shields deposited on top of and substantially surrounding the multiple layers of the MR sensor stack. Such a design is particularly advantageous in CPP designs in which the only spacing necessary between the side shields and the bottom shield is due to a gap layer. The integral top and side shields design works both with CPP heads having pile bias stabilization as well as those having permanent magnet abutted junctions or patterned exchange bias stabilization. In addition, the design is also advantageous in CIP heads having permanent magnet abutted junctions or patterned exchange bias stabilization. In this latter embodiment, it may be possible to reduce the profile of the permanent magnet and any conductors to increase the efficacy of the side shields.

Shielding method and apparatus using flexible strip

Abstract: A shielding method and apparatus for an antenna disposed on an elongated support adapted for disposal within a borehole. The shield providing predetermined attenuation of one or more electromagnetic energy field components as the field components interact with the shield. The shield composed of a flexible strip or cylindrical body and respectively comprising a transverse conductive element or a transverse slot therein. The shields being adapted to cover an antenna mounted on the support. The shields being compatible for use in conjunction with saddle, tilted coils or multi-layered tri-axial coils to produce a pure transverse magnetic dipole electromagnetic field. The shields are also used in methods for shielding an antenna disposed on a support to provide predetermined attenuation of an electromagnetic field component as the field components interact with the shield.

Method of thermal vacuum tests and device for realization of this method

Abstract: FIELD: space engineering. SUBSTANCE: proposed method includes placing the spacecraft in vacuum chamber and irradiating its external surfaces with thermal flux simulating solar radiation at change of spacecraft orientation relative to this flux. In the course of tests definite densities of thermal flux are set and angles of turn of spacecraft relative to normal to datum planes of sensors are measured. Simulation of external thermal flux is ensured through simultaneous change of angle of turn of spacecraft relative to said normal and density of thermal flux; synchronization of turn and change of density of flux is performed in accordance with definite relationships. Device proposed for realization of this method includes vacuum chamber with swivel unit inside it for mounting the spacecraft and solar radiation simulator including illuminating part in form of shield with lights, projection part consisting of mirror and lens optical system and input unit including scatterer and flat- convex lens; it also includes control damper located between illuminating part and input unit; said damper is used for control of illumination intensity and is provided with drive. Damper is made in form of two convergent shields whose planes are normal relative to axis of optical system and are shifted relative to each other; shields are provided with cuts forming flow section for thermal flux; cuts are made in form of square with center lying in optical system axis and diagonally coinciding with direction of motion of shields; damper drive ensures motion of shields depending on change in density of thermal flux falling on spacecraft under test. EFFECT: enhanced informativeness of tests; reduced testing time. 3 cl, 4 dwg

Enhancement of the current in a superconductor strip by means of curved superconducting shields

Abstract: The distribution of the sheet current in a superconductor strip located between superconducting shields of various geometries is studied on the basis of exact analytic forms. Whereas the current becomes increasingly uniform when flat shields approach the strip, strong inhomogeneities are found to develop for curved shields, with concomitant enhancements by several times of the maximum total current predicted in the marginal Meissner state; a trait which could be favorably exploited regarding superconductor electronics applications.

A general method for estimation of boundary conditions over the surface of shields surrounded by radiating enclosures

Abstract: An optimization analysis is employed to estimate the unknown boundary conditions over the surface of enclosures and shields in radiation equilibrium from the knowledge of the boundary condition over the surface of an enclosure surrounding them. The discrete transfer method is employed to solve the radiative transfer equation. The conjugate gradient method is used for minimization of a convenient objective function, which is represented by the sum of square values of net heat flux through the shields. The performance of the present technique is evaluated by several numerical experiments on two- and three-dimensional enclosure shield systems.

Variable progressive beam headlamp

Abstract: A vehicular headlamp in which the radial beam of radiated light is continuously adjustable between a first position and a second position. Semi-cylindrical lamp shields surround a lamp. The lamp shields are attached to gears which operate to rotate the lamp shields radially about the lamp. An actuator is attached to the gears, such the actuator can turn the gears in order to rotate the lamp shields. The actuator is controlled by a circuit which prevents over-rotation. The actuator may move in very small increments, such that the lamp shields may be continuously adjustable between the first position and the second position. The lamp shields are thus continuously adjustable to vary the projected radial beam of the headlamp.

One or more shields for use in a sputter reactor

Abstract: A set of shields usable in a sputter reactor that is used to form a tantalum-containing layer on a substrate. The tantalum-containing layer is formed using a physical vapor deposition technique wherein a magnetic field in conjunction with an electric field function to confine material sputtered from a tantalum-containing target within a reaction zone of a deposition chamber. A lower shield includes plural perforations through it to allow processing gas to pass from gas inlets in back of the outer shield to the processing space. An inner shield fits within the outer shield and shields the perforations from the substrate. An upper shield is disposed between the inner shield and the target and may be electrically floating.

Universal resilient shields

Abstract: A number of eyeglass frames with resilient structures and shields that have wide applicability are described. In one embodiment, an auxiliary frame has a resilient structure at its bridge area, and non-uniform shields. The shields have openings at their sides and retaining mechanisms. Due to its resilient nature, the auxiliary frame is adaptable to after-market sales for primary frames. In yet another embodiment, a primary frame has a resilient structure at its bridge area and has shields. Such a primary frame again allows it to be comfortably fitted to people whose heads are of different sizes and shapes.

Material efficiency in magnetic field shielding at low and intermediate frequency

Abstract: The efficiency of conductive and magnetic screens is analyzed in the large scale shielding of environmental magnetic fields up to 20 kHz. Several geometrical configurations of the shields and the field sources are reproduced in laboratory in order to analyze in a systematic way the mitigation properties. The problem is also faced by a numerical model, based on a hybrid FEM-BEM approach.

Waste toner detection device and electrophotographic recording means

Abstract: PROBLEM TO BE SOLVED: To surely detect the existence/absence of a waste toner box and the state of waste toner in the waste toner box while simplifying a device configuration. SOLUTION: A waste toner detection device is provided with a single photosensor 102 which shields light with waste toner when a fixed amount of waste toner or more waste toner is accumulated in the waste toner box 101 for accumulating waste toner removed from the surface of a photoreceptor formed with a transparent or translucent container, and a light shielding mechanism 103 which retracts from a detection area of the photosensor 102 when the waste toner box 101 is mounted and meanwhile, advances to the detection area of the photosensor 102 when the waste toner box 101 is removed from the device to make the photosensor 102 a light shielding state. The waste toner detection device determines the existence/absence of the waste toner box 101 and the state of the waste toner accumulated in the waste toner box in accordance with an output from the photosensor 102. COPYRIGHT: (C)2004,JPO

An efficient approach for reducing inductive noise using shield insertion [IC layout]

Abstract: An efficient technique to reduce the inductive noise is to insert shields among signal wires. These shields are quiet wires that are either connected to the ground or to the power supply. An efficient approach to determine the locations and number of shields needed to satisfy certain noise constraints is provided. We use an already existing noise model, which is flexible and fast, to be included in the core of our algorithm. Experimental results and SPICE simulations show that our approach is fast compared to the best-known approach and needs few number of shields to satisfy the noise constraints.

Steel sheet for magnetic shields and manufacturing method thereof

Abstract: A steel sheet for a magnetic shield comprising less than 0.005 % by weight of C and 0.0003 to 0.01 % by weight of B, and having a thickness of 0.05 to 0.5 mm and an anhysteresis magnetic permeability of 7500 or more.

Development of an Active Cancel System for Cylindrical Magnetic Shields

Abstract: We have improved the low-frequency axial shielding factor (ASF) of the open-ended cylindrical magnetic shield by incorporating the active canceling system to it. The amplitude and the phase of the incoming magnetic field to the shield were measured along the axis of the cylinder, and along lines on the inner and the outer surface of the cylinder in the frequency range 2 50 Hz. A simple feed-forward active canceling system has been developed, which consists of three canceling ring coils and a single monitoring flux-gate magnetometer. The magnetometer was located at a position on the outer surface of the magnetic cylinder, where the canceling magnetic field does not interfere to the magnetometer. The ASF achieved with active cancel was as high as 3000 at 2 Hz, 855 at 10 Hz and 113 at 50 Hz. These high ASFs can only be obtained with a longer magnetic cylinder if the active cancel is not employed.

Effect of intense energy fluxes on vacuum-tight rubber

Abstract: Vacuum-tight rubber is widely used in various structures. Composite shields protecting space vehicles against micrometeorites include natural-rubber-like materials, which are similar to vacuum-tight rubber in properties. It is, therefore, of interest to study the behavior of vacuum-tight rubber subjected to an intense pulsed energy flux. From the response of this material to a high-energy action, one can construct a behavioral model for natural-rubber-like materials used in the protective shields. The behavior of vacuum-tight rubber exposed to a high-energy pulsed electron beam (with an energy density of up to 600 J/cm2 and a half-width of 10−7 s) is investigated. The rate of material expansion toward the beam, as well as the velocities of propagation of strong and weak perturbations over the material, is measured. Spalls on the front and back surfaces of the sample are detected. The Gruneisen constant (a fundamental thermodynamic parameter that characterizes the pressure in a medium upon isochoric heating) is found.

Vertical magnetic head and vertical magnetic disk device

Abstract: PROBLEM TO BE SOLVED: To provide a vertical magnetic disk device preventing erroneous erasure which is caused when magnetic flux is leaked from edge parts of shields of a reproducing head which are opposed to a magnetic disk by intrusion of an external magnetic field into a magnetic head. SOLUTION: A vertical magnetic disk device is equipped with: a vertical magnetic head having a recording head including a main magnetic pole, a return magnetic pole and a recording coil, a reproducing head including a magneto-resistance effect film and a pair of shields arranged so as to hold the magneto-resistance effect film in-between, and a soft magnetic film arranged so as to surround the side faces and the upper part of the reproducing head; and a magnetic disk having a soft magnetic substrate and a vertical recording layer on a substrate. COPYRIGHT: (C)2006,JPO&NCIPI

Magnetic shielding of power plants in large facilities

Abstract: Large metal plates are used to as shields against magnetic fields at power frequencies. These fields are found to emanate, as an example, from high power transformers and their associated low voltage cables. These plates are finite and their shielding is compromised due to their finite dimensions. This paper evaluates the shielding afforded by such a plate, as related to the geometry of the placement of the source and victim and the dimensions and structure of the shield plate.