MacGregor and others (1998) described the power light source suitable for inactivation of microorganisms. The test assembly used for experiments consisted of a rectangular PVC housing, a pulsed generator and associated switching and controlled circuitry as illustrated in Fig. 1. Internally, the light source was mounted 4-5 cm above the 2 sample holders, which were set 45 degrees to the horizontal. This arrangement permitted 2 petri dish samples to be located at right angles and irradiated simultaneously, with each sample receiving the same average exposure. The light source employed was a Hearaeus Noble light XAP Series that was constructed from a clear fused quartz tube filled with Xenon to pressure of 450 torr. The dimension of the tube was 3 mm dia and 7.5 cm arc length. The tube had an enriched light trigger along the length of the envelope and was capable of being operated with an average power of about 100 W. The pulsed generator was a single stage, inverting PFN Marx generator, which was charged to 30 kV dc. The generator was fired using a trigatron via a high voltage auto transformer. The source capacitance of the generator was 6.4 nF and the source impedance, when fired, was 6.25 Ohms.