The Model 634 Deuterium lamp features a Magnesium Fluoride window, 1mm diameter emitting plasma and ~f/6 output. The source system includes cables, lamp housing and a power supply for lamp operation. This source is useful for vacuum ultraviolet (UV) and deep UV operation. Output between 380 and 165nm is continuous; below 165nm, molecular lines predominate. Because the sealing window is polished Magnesium Fluoride, cut with its optical axis perpendicular to its face, the source works to wavelengths as short as 115 nanometers. The Model 634 Deuterium lamp is available as a calibrated standard of spectral radiance.