Tube Failure

The flashtube end-of-life can occur in either of two modes, and we can distinguish between catastrophic and nondestructive failures. The factors that contribute to catastrophic failure are explosion of the walls due to the shock wave in the gas when the lamp is fired or overheating of the lamp envelope or seal and subsequent breakage because of excessive thermal loading of the lamp. The first failure mode is a function of pulse energy and pulse duration, whereas the second catastrophicfailure mode is determined by the average power dissipated in the lamp. When the flashtube is operated well below the rated maximum pulse energy and average power, the lamp usually does not fail abruptly. Rather, the tube will continue to flash with a gradual decrease in light output, which will eventually fall below a level necessary for the particular application. In the latter mode of failure, the reduced light output is caused by the erosion of the flashtube electrodes and of the quartz walls and by the gradual buildup of light-absorbing deposits within the flashtube envelope.