The design of large cryotron memories

While attractive for large random access stores, the cost of helium refrigerators limits the use of cryotron memories to sizes greater than about 10⁷bits. The batch fabrication of such large memories requires the use of an element having wide margins. Such an element is described and the design of a store using these elements is discussed. Both transit time delay and selection time constant are important in the design optimization, and transit time delay also limits the use of in-line cryotrons. Refrigerator power is shown to be a limit to speed and size. In the design of the storage cell, cell inductance is shown to be important and a cell design which gives a large loop inductance is described.