plasma toroid

I saw a fascinating and delightful plasma globe on a Royal Institute lecture called High-voltage physics - with David Ricketts. The globe starts at after about 58 minutes. Below is a snip of the globe showing a plasma toroid.



With a web search, I found a technical description and construction of the globe and plasma toroid
Attachment: PTTheory.pdf (1MB)
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Below is a snip of a plasma toroid from the paper


It does not require anything very complicated. The main components are a one transistor oscillator (50W,15MHz) and a vacuum pump (probably two stages). Unfortunately it uses Xenon gas but only 2l at 15torr (about 30ml at one bar). Apparently SLS sell 10l (presumed 1bar) for £737, so it's probably more than £100 for say 1l if it's available in small qualities. Apparently, Argon is not suitable due to its higher ionisation energy and lower atomic mass.

edit:
Perhaps Bromine with a similar ionisation energy as Xenon and more than half Xenon's atomic mass would be suitable. Apparently, a high atomic mass reduces the mobility of the plasma. Perhaps adding a gas with a much lower ionisation energy can operate at a higher pressure and hence reduce mobility of the plasma. Unfortunately, only mercury may have sufficient vapour pressure, but its ionisation energy is only slightly less than Xenon. It may be more practical to operate at a high loop voltage and higher pressure for the lower atomic mass gasses, such as Bromine and Argon.

[Edited on 10/22/2023 by wg48temp9]

Quote: Originally posted by Morgan

In the video of High Voltage Physics he showed a Kelvin Water Dropper much like the one Walter Lewin uses to demonstrate a tiny spark. It really seems a feeble example for such elaborate settings. This one does much better and it seems they could spring for something like this as well. Philipp Wasserstrahlengenerator - Kelvin Generator - Wasserfadenversuch https://www.youtube.com/watch?v=698F700PM2Y