THE CONTRIBUTION OF THE SOCIAL ENVIRONMENT TO HOST RESISTANCE: THE FOURTH WADE HAMPTON FROST LECTURE

An improved structure for a microwave generated plasma light source for emitting radiation in the ultraviolet and visible portions of the spectrum. Microwave energy generated by a microwave source is coupled to a plasma forming medium which is confined in a longitudinally extending tube. The tube is surrounded along its length by a microwave chamber, a portion of which comprises a means for reflecting the emitted radiation and a portion of which comprises a mesh-like member which is substantially transparent to the emitted radiation, but which is relatively opaque to the microwave energy. The microwave energy may be fed to the microwave chamber either from the end thereof, or from the top or sides if the microwave sources is housed in a waveguide located on the top or sides of the chamber. The plasma forming medium is confined at a relatively high pressure and the microwave energy is coupled thereto at a high enough power density to create electron densities in the plasma in excess of the cutoff density. Electrons are excited by the transformation of waves and wave absorption and collide with the heavy particles of the plasma which emit ultraviolet and visible radiation upon de-excitation.