Those lamps used in spark plug wires...

Those high voltage indicator gadgets used in series to spark plugs to tell the presence of high voltage pulses; are they a plain neon bulb or something else ?

----> https://i.ebayimg.com/00/s/MTkzWDMwMA==/$(KGrHqR,!g4E6Zgcvp7-BOw9JkVUew~~60_35.JPG

What about a xenon bulb from photoflash, would it equally work, or work much better ?

About the current, what to expect from a spark plug wire ?
About the bulb; being a neon, would it have a detrimental resistive current limiting ?
If a xenon, will the current limiting be much less and the flash more intense than neon ?

I have all the parts to make one with any bulb inside a huge clear fuse holder, but do not want to risk the survivability of 1" xenon tubes from my parts bin. What do I need to learn ?

They use neon bulbs that can trigger with 60V from near field radiation levels. Current limiting is essential as the voltage collapse near zero.

Xenon has a much higher trigger threshold and holding current.

back to back LEDs will work with a coil will pickup the signal as well. ( Must be reverse protected)

Thanks.
..."near radiation fields"... Do you imply there is no connection with the conductor and neon bulb lights up only by proximity to it ?
I made maaany years ago a dash display with four neons with one side grounded and the others to pieces of aluminium foil wrapped in each of the four cylinder wires, no ohmic connection. Worked perfect, showing the 4 firings.
I wonder if a xenon bulb in series with the wire would stay alive and yield much brighter light to see in sunlight conditions. I will have to try...