Abstract: An electromagnetic radiation transmitter/reflector device (1), an apparatus and a process implementing such as device. The device comprises a straight transparent quartz tube (2) with an end-to-end bore (3) for retaining a pressurised ionising gas extending therethrough around an axis (4) and defining the cross section of the radiation transmitter beam, and a surface (7) for reflecting the transmitted radiation, comprising two longitudinal side wings (14) symmetrical in relation to an axial plane (10) of the bore, said reflecting portion being at least partially secured to the tube.