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The use of a regular array. or lattice, of magnetic bubbles for the storage of information requires two kinds of functions: the read-write functions involving the generation and discrimination of bubbles with different wall structures, and the access functions involving the insertion and removal of bubbles at selected locations in the lattice. In a column-accessed bubble lattice device, accessing is accomplished by first translating the lattice to position the desired column of bubbles in an input-output access channel and then translating this column along the channel to a detector area outside of the lattice while simultaneously introducing new bubbles from a generator area at the other end of the channel. An analysis of the influence of device design parameters on access rate indicates that the most important parameters are the column translation rate and lattice capacity. A device is described that was designed to study the translation of a lattice of bubbles and of a single column of bubbles within the lattice. Quasistatic operating margins and dynamic measurements of this test device indicate that the column-access configuration provides feasible means for the rapid access of bubbles from a lattice. Table 1 Bubble diameter and feature size required for a storage density of 105bits!mm 2 •

The usual concept of a thin film or other open flux path magnetic element consists of the material itself closely encircled by drive and sense conductors. Strips of conductor of width approximately that of the element are attractive for several reasons, i.e., low resistance, low skin effect, and low line impedance. However,these strips, being closely coupled to the element, can severely influence its dynamic properties by means of induced eddy currents. These conductors manifest themselves in three ways: 1. A slowing of the switching due to the air return flux path of the element passing through a conductorand being damped. 2. A dynamic distortion of the air return flux due to shielding effects. 3. A dynamic distortion of an applied field due to shielding effects. All of these effects can be detrimental to the operation of the element. In this paper, approximate calculations are presented to show the extent of these effects. The geometry considered is that of a “conventional”flat thin film element, driven and sensed by strip transmission lines. Several drive and sense configurations are considered, and experimental evidence is presented in support of these calculations. Although the cases considered are somewhat arbitrary, the methods and many of the results are applicable to other cases of utilization of open flux path elements.

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