When this energy is released and dissipated it forms a highly excited xenon plasma within the flashlamp. The voltage to which this capacitor is charged is usually lower than that which would cause the xenon to ionize. Figure 1 shows typical flashlamp triggering characteristics. It should be noted that the curves are somewhat dependent on the triggering method and other factors external to the flashlamp itself. For instance, the arrows on the curve limiting the reliable flash area indicate how the curve typically migrates back and forth over the life of the flashlamp.
Most triggering schemes use a trigger transformer to produce high voltage pulses of short duration.
Several different circuits have been developed which introduce this voltage to achieve ionization. As the level of ionization increases, the streamer increases in cross section and produces an intense flash. Overvoltage Triggering 1. External Triggering External triggering uses a high voltage trigger pulse to create a thin ionized streamer between the anode and cathode within the lamp. Ionization starts when gas adjacent to the tube wall is excited by the voltage gradient induced by this high voltage pulse from the trigger transformer.