Ring-shaped Magnet Research Articles

Spinning rate decay of levitated high- Tc superconductors in rotational magnetic field

The rotation damping of a levitated superconductor was examined in the static field of a ring-shaped magnet and in the rotating field of coils. It was demonstrated that the pinning force mainly contributed to magnetic friction while the influence of a viscous component was negligible. The rotating magnetic field created a torque, reducing the angular deceleration under relaxation. Dependence of the rotational field-induced torque on the field-intensity was step-like. A relationship between the step-like behaviour of rotational field-induced torque and pinning center distribution is discussed. The origins of friction torque and rotational field-produced torque are discussed.

Compact ECR-source of ions and radicals for semiconductor surface treatment

A compact microwave ECR-source of ions and free radicals has been fabricated. It includes a stainless steel tube, ceramic microwave input and permanent SmCo 5 ring-shaped magnets. Its working pressure range is 10 −4−10 −2 torr using Ar, H 2, N 2 and some other gases. The maximum ion current density in a hydrogen discharge at 10 −3 torr reaches 3 mA cm −2 15 cm downstream with a microwave power and plasma stream diameter of 100 W and 8 cm, respectively.

Current Sensitivity of Plasma Voltage and Emission Line Intensities in a Planar Magnetron Glow Discharge Device

A coaxial arrangement of a ring-shaped ceramic magnet and a disk-shaped rare-earth magnet is used to trap plasma electrons in circular orbits near the surface of the planar cathode. This configuration results in the formation of a ring-shaped plasma which is stable at all pressures in the range 0.0007 Torr to over 10 Torr. A model is presented which describes the sensitivities of plasma emission intensities to the discharge current for atoms and ions of both the plasma gas and the sputtered flux of cathodic material. The model is based on the number of electron collisions needed to generate the radiating species. Experimental data for the species Ar, Ar+, Cu, and Cu+ are compared to the model.

Pressure Sensitivity of Emission Intensities and Plasma Voltage for a Planar Magnetron Glow Discharge

A glow discharge device is described which uses a curved magnetic field passing through the surface of a planar cathode in order to trap electrons near the cathode surface and thus obtain stable operation at unusually low pressures. The magnetic field is obtained from a ring-shaped ceramic magnet and a coaxial Co-Sm rare-earth magnet located directly behind the cathode. In Ar, the device operates over the pressure range 6 × 10−4 Torr to over 2.5 Torr with plasma voltage under 420 V. Plasma voltage vs. pressure data for Cu and Al cathodes suggest that several modes of operation occur over this pressure range. Emission intensity vs. pressure data are presented for Ar, Ar+, Cu, Al, continuum background, and some residual-gas band systems.

光ディスク装置用ムービングマグネット方式２軸アクチュエータの開発

This paper presents a lens actuator of optical head in an optical disc drive. A newly developed moving magnet method is applied to a two dimensional sliding and rotary lens actuator, and radically simplified. This method is to compose a magnetic suspension in focusing and tracking direction by means of yokes and a ring-shaped magnet magnetized in four pole at unequal intervarls, and the designing method of magnetic suspension is disclosed by a detailed magnetic field analysis. It has been further confirmed by analysis and experiment that the force in an undesired direction caused by movement of the magnet can be reduced by symmetrical magnetization. As a result, in driving force, control band and other characteristics, the same performance as in the moving coil type have been recognized.

Rotary Encoder Using Amorphous Star-Shaped Core Field Sensor

The authors describe a magnetic rotary encoder consisting of a ring-shaped multi-pole magnet and amorphous magnetic core multivibrator sensors positioned radially around the magnet. The frequency-modulated output is sinusoidal, with a distortion of less than 1% when operating at 50 kHz; the encoder is impervious to mechanical disturbances, and can be used at relatively high temperatures.

Shielding and generating uniform magnetic fields inside circular and noncircular cross-section dipoles

Using toroidal coordinates and Stokes streamline function, field and current distributions can be directly calculated for ring-shaped magnets with general cross section. In this paper, shield surface currents of circular, rectangular, and elliptic cross-section coils are obtained. We also discuss shielding against uniform external field and producing uniform internal fields inside the different cross sections.

Compact polarization-independent optical circulator

This paper introduces a compact polarization-independent optical circulator for communications using multimode optical fibers. This circulator consists of two pairs of rutile prisms used as polarization separators, a YIG Faraday rotator, a ring-shaped magnet, and a quartz halfwave plate. Insertion losses of 2.3 dB including fiber connection losses and isolations of 32 dB at a wavelength of 1.3 epsilonm were obtained using this circulator, and stabilization of the semiconductor laser was confirmed. Details on the design, fabrication, and characteristics of this circulator are presented.

Adjustable dual spider for a loudspeaker

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