Investment of Antenna-excited microwave discharge lamps with intensity, long life time and high luminous efficacy

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Antenna-excited microwave discharge (hereafter abbreviated by AEMD) has been extended to high pressure xenon excimer lamps with antenna gap of 1.0-1.5mm. The lamps filled with xenon gas at the pressure of 1.0-20 atmospheres were used to measure the lamp properties. Discharge of the lamps was sustained by continuous or pulse-modulated microwave power and 172nm line intensity from xenon excimer has been measured by the accumulated VUV power meter. It is found that the maximum of 172nm line intensity could be obtained at the continuous microwave power of 8W and the xenon gas pressure of 10 atmosphere. The pulse-modulated microwave lamp ignition has been examined to increase the line intensity. By adjusting the pulse frequency and duty ratio to optimize the xenon excimer production, the line intensity has been improved to 2 times higher than that from commercially available deuterium lamps. These xenon lamps radiate the VUV light from a small discharge column with the height of 1.0-1.5mm and diameter of 1.0mm. Therefore, this xenon lamp can work as a spot VUV light sources.Next, the microwave power propagation into the center of the AEMD lamps has been taken into account from the view point of electric circuit theory. It is pointed that the specific impedance of all parts used in the microwave circuit should be the same values as the lamp impedance. Furthermore, the reactance of the lamp impedance should be close to zero for the operation of power factor～1.Finally, the compact portable light engine for the metal halide lamp has been constructed using elliptic mirror coated by aluminum thin film for good light reflection. For the cost reduction and compact structure of the light engine, the matching elements in the microwave circuit have been removed. As a results, the proto-type light engine produced here has a rectangular parallelepiped structure with 50cm thick, 150cm long and 10cm wide, where the metal halide lamp is set up on the focal point of the mirror.