Bbc Brown, Boveri & Company, Limited

Walter Stoidl

Gerold Brandli

Robert Bachmann

Pieter Bearda

Rudolf Rieder

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.Hg of the mercury to such a value that the yield .eta. of the line of wavelength 2537 A, i.e. the ratio of the spectral radiation power for the wavelength .lambda.= 2537 A to the electrical power stored in the discharge, is at least 80% of the maximum yield .eta..sub.max for the chosen current density j.sub.O.

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Gebenstorf, Switzerland

Walter Stoidl