Tonite I was making the plasma ball effect in various incandescent and HID lamps with a BBQ ignitor. The noble gases in incandescent bulbs glow dimly, it is only seen in the dark. However I found that i could not make halogen GLS bulbs flash. A few did flash a bit in the capsules but none i could make flash in the atmosphere between the capsule and the outer bulb envelope. I doubt they are vacuum but what kind of gas is in these lamps? Certainly not argon. Can nitrogen be easily ionized with a bbq ignitor? I did make some decorative chandelier bulbs (these are mostly nitrogen filled) flash and they have a noticeably reddish hue added to the plasma filaments that formed from the leads to the outer envelopes.

If you means energy saver version of existing formats of halogen lamps, and not the energy saving retrofits for incandescent lamps in general, usually the said lamps have a IR coating that reflects IR back to the filament, so the filament can be underdriven and still operate at the same tempearture, reducing lamp wattage. However the lamp shape should be such, that the overall IR reflection from the coating back to the filament should be uniform (The reason why Philips until the recent time, used this design only in 12V halogen lamps). If the same IRC applyed to a plain design of a simple halogen lamp (Such as 230V double ended lamp), the IR reflection won't be uniform, causing significantly reduction of lamp life.

Other option of increase the efficiency of halogen lamp, so the wattage can be reduced without reducing the light output, is to use xenon or krypton instead of nithrogen.

Nithrogen should produces a red light. The halogen that used in halogen lamps, is mostly bromine but sometimes also chlorine, to prevent light absorption which is the characteristic of the iodine. Neon can't be used, since as an inret gas, it is the most inefficient gas. It cools the filament much faster than all other noble gases, so it usually used in signalling, where it cna cause the lamps to flash more sharply.

Many "halogen energy savers" use the outer just as a cover with no seal on the "filling" tube, so just the surrounding air.
Otherwise I would expect the Nitrogen, as the cheapest gas for oxygen and water free envelope.

I could imagine thecapsules to be made smaller than usually (to prevent internal gas circulation), thosewould then need better cooling than the air or nitrogen allows, so would be filled by something lightweight.
But I doubt this concept to be used on a cheap lamps - just for the cost reason...

In any case the fill has to be difficult to ionize, what makes the inert gasses rather problematic (requiring higher fill pressure,...)...

I would also assume just regular air inside the outer bulb.

UPDATE I just got a high frequency machine, intended as a skin spot remover but works kinda like a neon tester since it also contains a small tesla coil inside. I did tests on those halogen bulbs, they indeed do have a fill gas. The color in the outer atmosphere seems to be argon, likely with some nitrogen filled in. They don't ionize as easily as conventional incandescent bulbs however. The gases inside the capsule also ionized, seems like a dim deep blue, is this xenon?

Do these bulbs work normally after being plasma-ball-ized? Or do the filaments vaporize?

Do these bulbs work normally after being plasma-ball-ized? Or do the filaments vaporize?

The output power of the plasma balls or similar devices is just way too low to cause any damage, it would have to exceed the normal lamp power rating...