Bubble propagation and state control in the access column of a current accessed bubble lattice chip

Abstract

The on-chip electrical conductor circuits and sequences of current pulses used to propagate bubbles from the nucleator, through the access column, to the MR detector on a 1 Kbit bubble lattice chip are described in detail. The bubble propagation error rate as a function of bias field for both the isolated bubble and the closed-packed bubble regions of the column is described. A bubble logic function was performed on the chip to recover from isolated bubble propagation errors. The writing procedures for reliably encoding the bubbles into S = 0 and S = 1 wall states are described, and the error rates at which unwanted state conversions of the S = 0 and S = 1 bubbles occur in the column are given as a function of a state-stabilizing dc in-plane field. The over-all results tend to indicate that a practical device could be based on the use of bubble wall state encoding for the storage of information, but the bubble propagation bias margins of the present device are not adequate for reliably accessing the stored information.