Revisiting Claude Paillard’s triodes
One of the most enthusiastic responses we’ve ever gotten to a Make: Blog post was for the video of French radio ham Claude Paillard’s built from scratch vacuum tubes. If you haven’t seen the video yet, you’re in for a real treat. It still triggers passionate and effusive praise, such as this comment from a former Hughes Research Labs employee:
Dear Mr. Paillard,
I worked at Hughes Research Labs (now, HRL) for over 30 years and, vividly recall how skilled and talented the technical staff was. As a physicist, I relied immensely on our technical staff to fabricate the devices that we invented, without which, nothing would have become practical. It is magnificent to see and evaluate actual devices — made with such precision (as you so beautifully demonstrated) — evolve from our calculations and sketchy drawings. Your brilliant work brought back such fond and wonderful memories (you would have been hired on the spot!). In our laboratories, experimental and prototype lasers were made from scratch, just as you beautifully demonstrated with the triode. The gas discharge lasers required many of the skills that you posses, for this class of laser could be thought of as a “vacuum tube” with optical windows at both ends, and filled with a specified amount of spectroscopic purity, low pressure atomic or molecular gas(es), such as helium, neon, carbon dioxide, argon, xenon, etc. Moreover, such lasers require the vacuum-tube equivalent of a filament, cathode and anode to maintain a stable electric discharge, which is used to excite the active laser’s gaseous medium. In many cases, a “getter” was “flashed” in the tube (using external RF to heat it up as you so eloquently performed), and, the evaporated material such as cesium (the shiny coating one sees along the inner walls of the tube) is used to absorb contaminants (e.g., oxygen) that would otherwise render the device useless.
To those readers that have never worked in a research environment, it is easy to overlook all the fine skills that are necessary to actually fabricate a triode, each aspect of which is a specialty in itself: metal forming and machining, instrument design, vacuum technology, materials processing, high-power RF technology, glass blowing (including forming and annealing), understanding of the detailed device properties of a triode and how to characterize its electronic performance. Your work is excellent and, viewing your video is refreshing and inspiring, for you make an extremely difficult labor of love appear so effortless — true genius! Bravo to you!!
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