Abstract: A technique is disclosed herein for the enhancement of efficiency, and uniformity of light emission from a DC-operated fluorescent lamp. It involves the correlation of mercury vapor pressure within the lamp (which is dependent upon the temperature of liquid mercury within the lamp) with the magnitude and polarity orientation of the DC current applied to the lamp, and an optimization of these parameters along with lamp tube diameter.

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.