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Breakdown characteristics of high pressure xenon lamps

An investigation of the breakdown of high intensity discharge (HID) lamps filled with xenon at pressures from 0.1 to 5 bar is presented. Three power supplies were used in order to provide voltage rates of increase covering about four orders of magnitude from 5 mV ns−1 to 100 V ns−1, the latter being typical for electronic ballasts driving commercial HID lamps. Customized lamps ensure a volume breakdown between the tungsten tip electrodes of the lamp. Voltage and current waveforms were measured by means of electrical probes and the transient optical radiation was captured by a fast camera system. The breakdown voltage increases with growing pressure and voltage rate up to several 10 kV. Additional UV illumination decreases the breakdown voltage and reduces its mean variation. The experimental results were reproduced with good agreement by a fluid model taking into account the electron energy balance. The model shows an ionization front propagating towards the cathode. The front moves due to continuous field compression and relies on electron avalanches initiated by secondary electrons at the cathode.