Abstract: A method and apparatus for measuring the flying height of a slider supporting a magnetic transducer in-situ in a direct manner in an operational magnetic disk storage system. The method and apparatus produce relative motion between the magnetic transducer and a magnetic recording medium at a first velocity so that the resulting air bearing positions the magnetic transducer slider at a first flying height from the magnetic medium. A single signal of constant periodicity is written over a predetermined area of the recording medium by the magnetic transducer, and a readback signal is sensed from the predetermined area of the recording medium to produce a first signal. The flying height of the magnetic transducer slider is lowered to substantially zero, and a readback signal is sensed at the lowered flying height to produce a second signal. The first flying height is then calculated as the ratio, expressed in decibels, of the first and second signals times the wavelength divided by a constant.

Abstract: A close-packed magnetic bubble propagation device includes a pattern having a plurality of propagation elements positioned in at least four adjacent rows. These elements are spaced to provide a period or spacing of bubbles in these rows of less than three bubble diameters. Upon application of a rotating in-plane field to the elements, bubbles in adjacent rows move in opposite directions. A preferred embodiment of this propagation device has at least two storage loops which contain at least four adjacent horizontal rows of propagation elements. A preferred device utilizing this pattern has at least two storage loops and an access path which passes through each of the loops. An electrical conductor is associated with the propagation elements in the access path so that the passing of a current through the conductor together with the application of an in-plane rotating field to the elements causes bubbles associated with the elements in the access path to move along the access path.

Abstract: A bubble storage system includes a closed loop propagation pattern suitable for use with a bubble lattice. The closed loop propagation pattern is folded and contains, for example, segments of a hexagonal lattice connected by 60.degree. turns to obtain a close pack bubble storage configuration. The bubbles are propagated along the pattern consisting, preferably, of C-bar or chevron type permalloy elements by a rotating magnetic field in the plane of the pattern. In a preferred embodiment, the folded closed loop propagation pattern is surrounded by a region of non-propagating bubbles retained by permalloy dot confinement means. There are substantially the same number of elements in the propagation pattern as there are bubbles in the lattice that are affected by the propagation elements.