This video shows how to make a plasma tube out of a glass bottle and a high voltage supply that takes advantage of Paschen's law (https://en.wikipedia.org/wiki/Paschen...) to generate a long electrical arc from the reduced breakdown voltage of air in a lowpressure environment.

The bottle runs at about 0.1 atmospheres, so this would be considered a very low vacuum, but it's more than sufficient to demonstrate the relationship between breakdown voltage and pressure. A dedicated vacuum pump could evacuate this bottle down to a few thousandths of an atmosphere, and the same size arc could be generated with a few hundred volts instead of 30,000 volts.

Diamond hole bits used in the video:
https://www.amazon.com/gp/product/B01...

Music:
Serge Pavkin Technology For Life
   • Free Music / Documentary Background M...  
Serge Pavkin Intergalactic
   • Free Music / Ambient Background Music...