Cylindrical Film Memory Device Characteristics

This device is a single-bit storage element consisting of a 100-mil piece of 25-mil glass tubing with a 6000-A nickel-iron film coating. This paper describes those properties of the device which pertain to its operation in high-speed linear-word-selection memories. The device is used in the orthogonal mode, with an axial word field. The circumferential bit (digit) field coincides with the easy axis of magnetization, which is induced by a dc field during deposition of the film. The closed magnetic path avoids the limitation on thickness which exists in open-path elements. Thus, the cylindrical device can be designed to have large signals over a wide range of cycle times. Experimental data are included on the following characteristics: optimum device and drive-conductor geometry, effect on signals of one-zero duty cycle, sensitivity of stored information to disturbance by bit field and stray word fields, and drive-current requirements. The test specification developed from these data includes allowances for drive current tolerances, device temperature coefficient and information duty cycle. Sufficient quantities have been tested to this specification to show that this device is a workable, reproducible memory element.