RLOD#45 (2020.08.21) 1962 Philips LL103137E Zn

Electric discharge lamps filled with a single radiating element are useful in special applications such as spectroscopy, interferometry and refractomery, which require a well-defined line spectrum. Transition metals such as mercury, cadmium, and zinc are commonly used to that end and while the high volatility of mercury enables a high source brightness, the very low volatility of zinc limits the discharge operation to a low-pressure regime characterized by a low power dissipation. Philips used an unique burner design in order to ensure the highest vapor pressure possible of that element and to prevent its condensation on the wall between the electrodes: a quartz vessel stretched so as to maximize its wall thermal load, which is needed given than the LL103137E dissipates 13 W only. Typical of the company’s spectral lamps, the arc tube in this lamp is also provided with a pair of quartz diaphragms which keeps the cold-spot temperature high and limits the rate of burner blackening over time. The model shown here is a particularly early one, featuring an arc tube with vacuum-shrunk end seals and a frame supported at both ends of the bulb.