Stable glow discharge light source with close temperature control for sharp resonance lines

Claim 1

In a stable light source providing an output in a predetermined spectral range, the combination of: a lamp housing of low thermal conductivity comprising first and second blocks joined at inner faces thereof and including a passage along said inner faces with a larger central section and smaller sections on opposite sides of said central section; a glow discharge tube lamp charged with a solid metal or metallic halide having a vapor pressure at 20* C. substantially less than that of mercury and positioned in said central section of said passage; means clamping said blocks together on said lamp with said lamp supporting said blocks, one of said blocks including an output slot therethrough for radiation from said lamp; an electrical resistance heater having two heating elements mounted respectively on each side of and parallel with said lamp in said smaller sections of said passage; a first electric power source for said lamp providing a relatively high voltage and a relatively low current with respect to the voltage and current of an electric arc lamp; first circuit means for connecting said first power source to said lamp for producing a glow discharge in said lamp; a second electrical power source for said heater; and second circuit means for connecting said second power source to said heater to heat said lamp for increasing the vapor pressure of the charge material and producing a glow discharge in the metal vapor; with the lamp current being a function of the output of said first power source with the voltage drop across the lamp being substantially constant, and with the lamp temperature and therefore the vapor pressure in the lamp being a function of the output of said second power source.