Numerical description of high frequency ignition of fluorescent tubes

The effect of the frequency on the breakdown time in a straight discharge tube is investigated by means of a fluid model. The discharge tube is similar to a compact fluorescent lamp tube, contg. argon at 3 Torr and mercury at a few Torr. The mechanism of breakdown at frequencies of the order of several 10 kHz is considered and related to breakdown at a dc voltage. During a neg. potential on the powered electrode, an ionization wave traverses the tube in a way similar to that in a dc operated tube. During a pos. potential on the powered electrode, the elec. field in the part of the tube already traversed by the ionization wave is enhanced by neg. charge on the inner wall of the tube. Although the ionized region does not extend during this phase, the ionization d. increases substantially. Furthermore, we investigated the dependence of the breakdown time on the applied frequency and found that the breakdown voltage is independent of the frequency. This is shown to be consistent with exptl. data. [on SciFinder (R)]