An LER LUWPL source luminaire having a magnetron heat conductingly mounted below a finned heat dissipater with a suspension eye. The magnetron is attached to a microwave transition and a lucent crucible. An imperforate cover extends down from the heat dissipater and is closed by a transparent screen, held by a molding. A generally square shaped molding supports a polished-sheet-metal reflector (having four triangular faces, pyramidally arranged, with a square base embodied by a rim supported on the top of the screen above the molding) extending back to the lucent crucible, with its reflective surfaces obliquely facing both the crucible and the screen for reflection of light from the crucible out of the luminaire via the screen. The faces converge to a virtual apex, on the central axis of the lucent crucible. This axis is coincident with the pyramid's normal axis from the apex to the center of the base.