Abstract: A discharge tube arrangement comprises a launcher and a discharge tube positioned in part within the launcher. When the launcher is energized with radio frequency (r.f.) power, surface waves are excited in the discharge tube which contains a fill. An electrically conductive structure extends along the discharge tube and is connected to an earth when in use. The structure is separated from the discharge tube by a radial distance such that, in use, the discharge tube produces an increase in total light output over the total light output of a discharge tube not having this structure. The structure comprises an insufficient quantity of material to obscure this increase in total light output.

Abstract: A discharge tube arrangement includes a discharge tube of a light-transmissive dielectric material and containing a fill. An excitation device for exciting surface waves in the discharge tube comprises an r.f. power generator and a launcher. The launcher is formed as an inner tube, an outer tube coaxial with the inner tube, and first and second end walls, at least one of the first and second end walls having an aperture for receiving the discharge tube. Means are provided inside the launcher for coupling r.f. power to the inner tube. A body of dielectric material extends from the inner tube to the outer tube, thereby to hold the tubes in fixed relative positions, the body encasing the coupling means.