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Observations of arc behavior utilizing a high speed-video camera and measurements of the current flowing in a rail electrode using several pickup coils have been performed to gain information for designing a small bore electromagnetic accelerator. Arc behavior is divided into two modes classified by arc current and the space between insulators in a square bore. A single arc column is found when there is a small arc current and a wide space between insulators ('Single arc mode'). On the other hand, several arc columns appear simultaneously when the current is high and the space between insulators is narrow ('Distributed arc mode'). To effectively accelerate a projectile to a high velocity, it is necessary to maintain a 'Single arc mode' and avoid the 'Distributed arc mode' which results from restriking between the electrodes. The space between insulators proves to be an important factor in the design of hypervelocity and small bore electromagnetic accelerators.

Domain configuration of the nonoriented Si-Fe electrical sheets with different grain size was observed decreasing their sheet thickness by using the Kerr effect. It was found that the nonoriented sheet needs multiple grains in the sheet thickness direction to eliminate the normal magnetization component in the flux closing structure causing excessive eddy current loss. Index Terms--Anomaly factor, domain structure, grain size, nonoriented Si-Fe electrical sheets.

Lower flying height provides higher recording density in hard disk drives. The gas lubricating film thickness (flying height) between the magnetic head and the disk has been reduced to under 50 nm and various designs for the air bearing surface of the head slider have been discussed. To obtain high flying stability in very Low flying conditions, it is important to achieve a high air bearing stiffness and to reduce the flying height fluctuation during head motion over the disk surface. We simulated the flying characteristics of the slider with shallow step air bearing pads and compared the simulated results with the experimental results. We also analyzed the air bearing stiffness, the flying characteristics during seek motion, the altitude sensitivity and the flying fluctuation due to the major manufacturing tolerances. The newly designed sliders have good characteristics for achieving a flying height around 25 nm. Index Terms--head disk interface, air bearing surface, flying head, slider design