fig1 and 2 the discharge device 10 comprises a vitreous glass envelope 12 which includes a generally cylindrical portion 14 a closed top portion 16 and a base portion 18 the generally cylindrical portion 14 includes a circumferentially thinned band portion 20 which is thinned to permit a high percentage of ultraviolet radiation to be transmitted therethrough a plurality of electrical lead ins 22 are sealed through the envelope base portion 18 and respectively operatively connected to the internal elements of the discharge device the discharge is generated by maintaining a potential between the plate like anode 24 and the coil cathode 26 which is heated to emit electrons by passing a heating current through the coil cathode 26 the coil cathode 26 is spaced from the anode 24 and a discharge confining baffle means 28 disposed between these electrodes and about these electrodes a cone shaped aperture 30 is provided in an arcuate portion of the baffle between the anode 24 and cathode 26 the discharge path is concentrated and directed through this cone shaped aperture 30 the anode 24 and the cone shaped aperture 30 are aligned with a generally rectangular aperture 32 provided in a wall of baffle means 28 while the coil cathode 26 is offset from this alignment this offsetting of the cathode 26 produces a discharge path which follows a 90 u00b0 bend in proceeding from the cathode through the cone shaped aperture 30 to the anode 24 the circumferentially thinned band portion 20 of the envelope 12 is disposed about this alignment of the anode and the respective baffle apertures 30 32 the output ultraviolet radiation is particularly directed through.