LOW WATTAGE HIGH PRESSURE SODIUM VAPOR LAMPS

摘要

A high pressure sodium vapor lamp arc tube comprising a tubular envelope of alumina ceramic having end closures supporting thermionic electrodes and containing a filling of sodium-mercury amalgam in excess of the quantity vaporized. In the smaller sizes of lamps from about 300 watts down to 50 watts, the arc tube bore has an important effect on efficacy, and a correlation exists between lamp voltage drop and optimum bore for a given power input. A bore of 5.5 millimeters is near optimum for a 150 watt lamp operating at a lamp voltage drop of 58 volts, and is also suitable for a 250 watt lamp operating at a lamp voltage drop of 98 volts.