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Question

Can a gas discharge tube with a perfectly sealed glass tube operate indefinitely? Or do the ions get "used up"?

Further detail

My (limited) understanding of gas discharge tubes is that a voltage is applied between the cathode and anode at opposite ends of the tube. Electrons escape from the cathode due to the strong electric field and may bounce into gas particles with enough energy to dislodge more electrons. With high voltage and low pressure, this collision-electron-generation process can cascade to form a "non-thermal" plasma of free electrons, cations, and neutral gas particles. From what I've read, the glow comes from photons released during de-excitation of gas particles (and maybe ions).

Any corrections to this summary would be greatly appreciated.

Eventually, wouldn't all of the gas particles get converted to cations and collect at the cathode, while all the free electrons would flow to the anode? And then the gas discharge and current across the tube would stop?

nitrogen gas discharge tube example

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Once the positive gas ion hits the cathode (= roughly an infinite bucket of electrons) it neutralizes and flows back into the tube as neutral gas. You're right that otherwise the discharge would be quite short-lived.

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