Abstract: The invention relates to an apparatus for sterilizing liquids by means of ultraviolet rays, using as the radiation source a low pressure, high current, mercury vapor lamp (UV lamp) which is provided with an appendix-shaped piece of tube (appendix) located on the discharge tube. In order to be able to regulate the temperature of the appendix in a defined manner even while the lamp is in operation and in order to achieve longer life of the UV lamp, an airstream circulating through the apparatus is used to cool the UV lamp. This airstream follows a path such that the air warmed on the discharge tube travels past the electrode bulbs of the UV lamp to the outer wall of the pipeline, through which pipeline the liquid to be sterilized flows. The air which has cooled on the outer wall of the pipeline is then returned to the UV lamp and must be at a temperature which is lower than the operating temperature of the appendix, so that the temperature of the latter can be regulated in a defined manner by means of a heater.

Abstract: Apparatus for generating ultraviolet radiation of high spectral radiance whereby the radiation is produced in a discharge tube having a thermoemissive cathode and a discharge space and filled with mercury/argon by means of a wall-stabilized direct-current gas discharge at a mercury pressure p.sub.Hg of between 5 .times. 10.sup.-.sup.3 and 5 .times. 10.sup.-.sup.1 Torr and a current density j of the discharge current I of between 1 and 25 A/cm.sup.2. The discharge tube incorporates a pressure-equalizing space connecting the cathode space to the anode space whereby the sum of the volumes of the cathode space, anode space and pressure-equalizing space is greater than the volume of the discharge space. The pressure of the argon is maintained between 0.01 and 10 Torr. A first control element is provided which regulates the current density j of the discharge current I to a constant value j.sub.O between 1 and 25 A/cm.sup.2. A second control element is provided which regulates the pressure p.sub.