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DEUCE Mercury Delay Line Memory

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Original question:

The Deuce memory was mushroom shaped and stood vertical - why?

From: John Deane, November 28, 2010
Hi folks,

I passed on Ed's comments to three folks who worked on UNSW's DEUCE: Robin Vowels, Keith Titmus & John Webster. Here's a somewhat edited version of their responses, plus photo.

John Deane


English Electric DEUCE, eg University of NSW's "UTECOM" - Mushroom Memory

The memory consisted of 12 mercury filled delay lines. These were "folded" with quartz crystal transmitter and receiver at the top and a pair of acoustic mirrors at the bottom. See photo 1.

The delay lines were arranged inside the periphery of an upright cylinder.

The transmitter and receiver driver electronics were arranged in a ring around the top of the cylinder, so as to be close to the corresponding crystals in the mercury delay lines. That provided easy access to mercury delay lines, and to the receivers and transmitters, for maintenance. In the case of the delay lines, for adjustment of position of the crystal transmitters for length of column and direction. In the case of the transmitters/receivers, for ease of removal and testing, connection and disconnection of cables. See photo 2.

The temperature of the delay lines was maintained by heating the cylinder, under thermostat control, to about 48 degrees C, within less than +/- 0.25 degrees C. (those numbers should be checked). The mushroom shape was achieved only when the lid was put on. It was shaped like an inverted dish so as to prevent heat escaping. See photo 3.

So, the cylindrical shape provided the smallest volume to be heated and allowed a consistent, short distance from the delay lines to their driving electronics. This was not an unstable shape. The lid was light (made from aluminium?). The cylinder was the heavy part, and as its base directly beneath the mercury tanks, was inherently stable.