Characterization of magnetic bubble generators

Two types of magnetic bubble generators suitable for a field-access bubble memory have been tested at 1.00 kHz bit rate at in-plane rotating fields above 15 Oe. The bias field margins of the generators at 30 Oe rotating field are equal to or greater than those of loop propagation. Both designs are based on the principle of stretching and cutting seed bubbles circulating around a Permalloy disk. Functions of stretching, cutting and transferring in the generator sequence are accomplished either with Permalloy elements or pulsed current conductors. The operating conditions of the generators in terms of current pulse amplitudes, widths and phase angles are presented. Among the two designs, namely Permalloy-stretch and conductor-stretch generators, the latter has a wider phase-angle margin.