I would like to modulate the plasma within an ordinary 10W fluorescent tube at an audio frequency. The planned input is a stereo Hi-Fi amplifier fed into a step-up transformer. Ideally a stock standard PA or 240V mains type.

How do I provide a de-ionization path so the tube does not just remain continuously lit once struck? In other words, what type of signal and applied to which parts of the tube?

I am thinking to apply the HV from the transformer secondary across both ends and wrap a grounded wire around the length of the tube. Or alternatively, a positive-going signal to one end and negative to the other.

Would either of these work, or any suggestion that would?

 

The plasma will self-extinquish when the voltage falls below a certain point, that point depending upon the gas mixture and the electrode spacing among other things.

I would more concerned about getting the gas into conduction. Remember you might need to drive the filament get it to "go".

 

I have done similar things with very low frequencies applied so the tube can be seen to flash. With audio frequencies, there is no way to visually determine if the gas is fully extinguishing between cycles. I suspect it does not, but would like to understand more before proceeding.