Below are photos of a replicated Tesla brush bulb at various RF power levels. The bulb is directly connected to the high tension winding of a high power RF source, ultimately connected to only the carbon button. This bulb shown, as it is Tesla’s design, proves to be very tentative and problematic, as the carbon and aluminum present within the bulb tends to outgas during operation, causing a decrement in the bulb’s vacuum.

Photos shown below indicate medium RF power level supplied to bulb, to lowest levels applied, (top to bottom).