RLOD#21 (2020.05.27) 1986 Narva HgE/3

Because of their high brightness and consistent spectral output, mercury arc lamps have long been a useful light source for all sorts of scientific and technical applications. Narva of East Germany began developing special lamps to that end during the 1950s, first by modifying and adapting conventional low-pressure discharge tubes, and then by designing specific high-pressure mercury lamps whose designed varied depending on the intended usage. The HgE/3 shown here is a late compact high-pressure mercury lamp aimed at spectroscopy and instrument illumination. Its overall construction borrows heavily from radio tubes, while its 40 W arc tube has a special design that includes metal diaphragms placed in front of the electrodes, a feature first introduced by BTH of England in 1935. One of them is used as an auxilliary electrode for the discharge ignition. These diaphragms serve the triple purposes of stabilizing the arc, of limiting the rate of wall blackening over time, and of blocking off incandescent light emitted by the hot electrodes. These increase the benefits and useful service life of the lamp in its applications.