Positive column

(Cathode light and positive column) and voltage distribution in a low-pressure gas discharge with cold cathodes

The positive column is the self-neutralizing part of a gas discharge; Ionization by electron impact and particle losses by diffusion are in equilibrium.

The positive column provides the majority of light and ultraviolet emission for fluorescent tubes and fluorescent lamps.

Since the lighting of the positive column does not fill the entire discharge chamber during a constant-current charging (especially during long-term operation), fluorescent tubes and fluorescent lamps can only be operated with alternating current.

In the case of glow lamps, the positive column does not appear - only the cathode is covered by the cathode skin and the negative glow light (see glow discharge).

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