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High-Pressure Mercury Lamps¹
Recently, both in the USSR and abroad, mercury arc-discharge lamps operating at high mercury-vapor pressure have been developed and studied. Since in these lamps large powers are expended in very small volumes, they are distinguished by very high brightness with small dimensions of the luminous region. This also makes such lamps very convenient for various projection devices. Since, owing to the high density of the mercury vapor, a redistribution of energy in the discharge spectrum takes place,² the spectrum of such a source proves to have, alongside a rich ultraviolet part, a considerably enriched visible and infrared part; therefore these lamps are of great interest also as light sources when working with monochromators.
The newest lamps of this type, placed on the market by several American firms, have the following data. Total luminous flux 65,000 lm, power 1000 W, operating voltage 840 V, current 1.25 A; service life under a specified regime: 25 min of operation, 5 min of rest—50 h. These lamps have the form of quartz tubes (external diameter ~6 mm, internal ~2 mm) made of quartz, fitted at the ends with metal caps. The total length of the whole lamp (with caps) is ~80 mm. The length of the luminous region is about 25 mm. The lamps are filled with mercury vapor mixed with argon.
These lamps can operate on both direct and alternating current. In the first case they must be provided with a ballast resistance; in the second, with a ballast inductance, or be supplied from a special transformer. In addition, they must be cooled with running water.
N. Khlebnikov, Moscow
Literature
- Journ. Appl. Phys., Oct., 1938.
- E. Lax, M. Pirani, and R. Rompe, Uspekhi Fizich. Nauk, 16, 39, 1936.