This ampoule was especially made for experiments with high voltage.
This tube does not contain any other “starter” gases, just pure SnI4. It needs a certain temperature to “ingnite”. Put the ampoule under boiling water to increase the pressure inside. Once illuminated the ampoule keeps the ideal temperature for continuous illumination.
On the picture you see the illuminated ampoule. Connected to a 5000V/35kHz transformer via two metal loops. The transformers can be found here.