Abstract: A reheat burner (1) includes a channel (2) with a lance (3) protruding thereinto to inject a fuel over an injection plane (4) perpendicular to a channel longitudinal axis (15). The channel (2) and lance (3) define a vortex generation zone (6) upstream of the injection plane (4) and a mixing zone (9) downstream of the injection plane (4) in the hot gas (G) direction. The mixing zone (9) includes a high speed area (16) with a constant cross section, and a diffusion area (17) with a flared cross section downstream of the high speed area (16) in the hot gas (G) direction.