The generation of EUV light includes rotating a cylinder at least partially coated with a plasma-forming target material, directing pulsed illumination to a first set of helically-arranged spots traversing a material-coated portion of the rotating cylinder in a first direction and directing pulsed illumination to a second set of helically-arranged spots traversing the material-coated portion of the rotating cylinder in a second direction, the pulsed illumination being suitable for exciting the plasma-forming target material.