There is an old GE databook on Neon lamps online that discussed adding radioactive gas to certain (apparently not all) lamps and why. Once I downloaded it I lost track of where I found it.
I worked at a small electronic fluorescent ballast company in the mid-90's and my boss contracted a consultant physicist who shared a patent and lawsuit against a magnetic ballast company with two other people.
The consultant told me a plasma is formed in arc lamps, with a negative resistance (as defined by the slope of the v-i curve) being the reason a ballast (resistance or impedance) is required to stabilize the plasma current. He said the association of power being produced by a negative resistance wasn't applicable in that application, just the dynamic v-i curve.
The peculiar choice of the term ballast (I wondered) was an analogy to a nautical ship ballast, which stabilizes the vertical orientation of the ship.
Murray
--
Murray
murrayatuptown