International Business Machines Corporation

Seagate Technology Incorporated

Erich Sawatzky

Wen-Chuang Ko

Moris Musa Dovek

John S Foster

Luis P Franco

Roland Eugene Imboden

Donald K Lam

An improved media defect glide test head assembly which incorporates a wide thermo-resistive (TR) element suitable for detection of thermal asperities on the surfaces of magnetic recording discs. The TR element of the inventive glide test head assembly is very wide when compared to magneto-resistive (MR) elements in normal MR read/write heads. In the currently preferred embodiment, the TR element is envisioned to be as wide as is possible to fabricate on the trailing edge of an air bearing element of the glide test head assembly, to enable detection of thermal asperities across a relatively wide band of disc surface during each disc rotation, thus enabling rapid testing of the media surface. In a second aspect of the invention, the wide TR element is envisioned to be formed of nickel or other material having a large thermal resistance coefficient. In a third aspect of the invention, the wide TR element is envisioned to include intermediary taps which permit more precise mapping of the location of thermal asperities. Control logic for implementing mapping of TR-detected disc defects is also disclosed.

Thermo-resistive glide test head for disc drive recording media

A contact magnetic recording rigid disk file utilizes a magnetoresistive (MR) sensor for reading data recorded on the disk. The disk file may be of the liquid-bearing type of contact recording with the MR sensor supported on the trailing end of a carrier which rides on the liquid bearing. The performance of the disk file is enhanced by including means for minimizing the effect of a discovered baseline read signal modulation. The modulation has been determined to be caused by variable cooling of the temperature-sensitive and temperature-elevated MR sensor by the disk, with the temperature variation being directly related to the variation in head-disk spacing caused by the waviness of the surface of the disk. A filter may be incorporated into the read signal processing circuitry of the disk file to eliminate the modulation, the MR sensor may be designed to operate at selected parameters to minimize the effect of the baseline modulation, and the portion of the carrier in contact with the disk surface may be selected to have a length less than the period of the disk waviness so that it more closely follows the disk surface topography.

Contact magnetic recording disk file with a magnetoresistive read sensor

In the bombardment of targets with beams of charged particles, a method for varying and controlling the diameter of such beams by passing the beam through an envelope of conductive material; the envelope is spaced from and coaxial with the beam. A selected D.C. potential is applied to the envelope, and the beam diameter is controlled by changing this applied potential in a direction away from ground potential to increase the beam diameter or by changing the potential in a direction toward ground potential to decrease said beam diameter.

Method for varying the diameter of a beam of charged particles

In an ion implantation apparatus, a structure for measuring the beam current at the target wherein a Faraday Cage is formed by walls adjacent to and electrically insulated from the target in combination with the target, means for biasing the target at a negative potential, means for biasing the walls at ground potential and means for measuring the target current and the wall current and for combining the two to provide an accurate beam current measurement.

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San Jose, CA, United States of America

Erich Sawatzky