Many x-ray tubes, used by crystallographers and others, operate with the aid of a tungsten filament in the region of 2500°K, The high operating temperature results in evaporation of the filament material with two serious consequences. The first is a finite but relatively short lifetime. The second is contamination of the target and windows with tungsten. In addition, if the tube is of the demountable type, connected to an oil-diffusion pump and a mechanical fore-pump, carbonaceous deposits can be a problem. In a typical tube, the filament is mounted within a centimeter or two of the target. The resulting radiant heating of the target presents additional cooling problems especially with low melting-point targets. Many if not all of the above objectional features are circumvented by a plasma controlled x-ray tube using a low pressure atmosphere of helium and a cage-like cathode fabricated from nickel wire-mesh. An experimental model has been operated for several hours at 15 kv and 10 ma on an aluminum target. Scaling up of the apparatus will permit power dissipations in the kilowatt range limited mainly by the available power source or vaporization of the target material.