Abstract

A microwave generated electrodeless lamp using a single magnetron, and an improved lamp envelope therefor. An elongated lamp envelope containing a plasma forming medium is disposed in a microwave chamber comprised of a reflector and mesh. The reflector includes a pair of coupling slots, each of which is disposed equidistant from the ends of the lamp envelope. A waveguide means is provided which has a wall which is comprised of a portion of the reflector which includes the slots, and has means for introducing microwave energy thereto at an area equidistant from the two slots so that the energy couples equally to the slots. When the frequency of the microwave energy and chamber dimensions are arranged so that a symmetrical standing wave exists in the chamber, a balanced system results wherein after a short start-up period, approximately equal light output is obtained from the respective ends of the lamp envelop. In order to prevent re-condensation of the envelope fill during operation at areas of low temperature, an improved envelope is provided in which such areas are severly tapered to cause hotter operation thereat.