Decorative xenon plasmas, 20-80 torr
Channel: Carl Willis
Date: 2013-01-15

Four 500-ml borosilicate Florence flasks are filled with xenon at various pressures between 20 and 80 torr (mmHg) and sealed off without any electrodes penetrating the glass.  In the video (after an intro featuring a large 1-liter flask at 50 torr) I show these low-pressure gas volumes being excited by high-frequency (5-50 kHz), high-voltage (~5-30 kV) current capacitively coupled into the flask via a cup of tapwater in which the flask rests.  At the lowest pressure (20 torr), xenon exhibits a diffuse, emerald-green glow that fills most of the volume but isn't particularly dynamic.  Even lower pressures result in similar discharges that are increasingly dim as the pressure is reduced.  At the highest pressure shown (80 torr), the electrodeless discharge becomes challenging to strike, but it has frenetic dynamics, sensitive touch response, and great contrast between diffuse green elements and brilliant-white filamentary arcs.  The other two flasks show intermediate pressures at 40 and 60 torr.  If I had to recommend a favorite, it would be the 40-torr effect. As always, questions and comments are appreciated!