Design consideratons and performance of a detector for contiguous-disk bubble devices

A destructive readout (DRO) detector structure for ion-implanted bubble devices employing a current activated expander is described. The design has been evaluated using 1-μm diameter bubbles, in devices with a storage cell area of 18 μm². Bias field margins of ∼10 percent are achieved and are compatible with other components on the chip. The detector has been operated at drive field frequencies between 100 and 400 kHz, and over a temperature range of 30°C to 80°C. Results show that the device can be operated over a reasonable temperature range without recourse to temperature tracking of the control currents. Signal sensitivities of 3 mV/mA are reported, and experimental data show that signal levels of 4 mV/mA (or 12 mV assuming nominal operating conditions) are quite feasible by reducing the spacing between the sensor element and the garnet film. Signal amplitude is independent of chip temperature during normal operation.