POWERHOUSE COLLECTION

Notes

Hollway writes of the project: "Contributors to the Counter Tube Project "In May 1947 the proposal to develop a single vacuum tube which would count electrical pulses, or waves, in the scale of ten, was suggested to the Chief of the Division of Electrotechnology, Dr. D. M. Myers, by D. L. Hollway and A. M. Thompson. Myers was enthusiastic. (Later, when Myers left to become Professor of Electrical Engineering at Sydney University, Mr F. J. Lehany became Chief of the Division of Electrotechnology and continued support for the project.) "It was decided that the design to try first would use an electron beam which could be locked into a number of stable positions, denoting the digits 0-9. Each position would be held by dividing the beam current so as to produce the required voltages on deflecting electrodes. "Thompson prepared a drawing of the X-Y design (tube number 1) and Hollway one of the secondary emitting version (tube number 2). But before these were started, 3 or 4 simple tubes to test electron guns and secondary emitting electrodes were constructed. "These tubes were made in the CSIR Division of Radiophysics Valve Laboratory, situated in the Electrical Engineering Department of the University of Sydney, under the supervision of Professor R.E. Aitcheson. "The initial tests showed some promise, but it was clear that a great amount of work would be needed to design and develop a successful counter with the speed, stability and other characteristics essential to interest manufacturers. "In 1948, Aitcheson left to spend a year or so at Bristol University, so Myers arranged with Dr. Bowen, Chief of the CSIR Division of Radiophysics and Professor Madsen (Professor of Electrical Engineering at Sydney University) for Hollway (who had experience in vacuum tube development and manufacture) to move to the Electrical Engineering Department and take over supervision of the Valve Laboratory and develop the counter. As that laboratory consisted of only two or three very able and experienced people working on Radiophysics projects, little supervision was needed and he was able to work almost full time on the counter tube. "The chief problems were discovered almost immediately. For example: to achieve the necessary speed, a high perveance (high-current at a low voltage) electron beam was needed. But, unlike the high-voltage beams in cathode ray tubes, dense, low-voltage beams tend to blow themselves apart, and cannot be focussed into a small spot after travelling far from the focussing lens. This restricts the path length, and therefore the sensitivity of the deflector system and explains the complex shape of the deflector electrodes. Similar constraints govern the collector design and other electrodes. "In finding a balance between these conflicting requirements, Hollway originated designs and tested models in the electrolytic tank (an analog computer for tracing electron paths) and electrode systems in a demountable vacuum station. "The small and intricately shaped electrodes were made and assembled with great skill and accuracy by Mr. H. Flood, who worked on the project full-time. The expert glassblower (whose name, unfortunately, I do not have recorded) made the bulbs and the special, 12-pin, powdered-glass bases. Mr. A. James pumped and processed the tubes. "All these people contributed to the development of the successful counters made in 1949/1950. ... [T]his stage in the counter tube development coincided with the arrival of transistors. It became clear that transistors soon would take over low-power functions such as counting, and the project was terminated."