Patent GB-959275-A (GB)
Title: Electrodeless discharge lamp apparatus
IPC: G01J3/42
Filed: 1960-02-16
Abstract: 959,275. Discharge lamps. VARIAN ASSOCIATES. Feb. 16, 1960 [March 3, 1959], No. 5506/60. Heading H1D. [Also in Divisions G1 and G3] Electrodeless discharge lamp apparatus comprises an alkali metal vapour discharge lamp, means adjacent to and outside of the discharge region of the lamp for exerting a discharge and means for maintaining the temperature of and the vapour pressure in the discharge region at values such that the radiation from the lamp is confined within a narrow frequency band of less than 10 kmc/s. In the construction shown in Fig. 1, the discharge lamp 11 has a portion 13 containing alkali metal 14 in a thermallycontrolled region 16 and a portion 12 surrounded by an energizing coil 26 in an independently thermally-controlled region 15. The regions 15 and 16 are defined by a cylindrical insulating wall 17 of glass wool and a partition 18 of lava. The temperatures of the regions 15, 16 are monitored by indicators 21, 22, such as thermometers or thermistors, and the temperature of region 16 is controlled by a heating element 23, e.g. of " Nichrome " (Registered Trade Mark) wire, coupled to a heater supply 24 which is variable by the inclusion of a variable transformer. The coil 26 is energized by radio frequency power from source 25 which can be a constant current oscillator the output of which is made variable by controlling the screen voltage or other parameter of the output tube. The excitation frequency from source 25 may extend from about 1 mc/s. upwards to frequencies in the microwave region and is preferably 30-100 mc/s. Instead of using the coil 26 the lamp 11 can be placed within a microwave cavity resonator or between the plates of a capacitor. The radiation produced by the discharge is emitted through a glass window 19. In the construction illustrated the coil 26 controls the temperature in region 15. The regions 15 and 16 are maintained at about 130‹ and 100‹ C. respectively, for a rubidium lamp filling and at about 250‹ and 200‹ C., respectively, for a sodium filling, corresponding to a vapour pressure of about 1 micron. Argon or the rare gas at a few mms. pressure can be added to aid starting. The temperatures of regions 15 and 16 can be adjusted by manual control of the sources 25 and 24 or automatically by obtaining electrical signals from the indicators 21 and 22 and feeding them to the sources 25 and 24. Fluctuations in spectral quality of the radiation due to power supply can be eliminated by the lucite rod 31, photocell 29, amplifier 33 and switch 27 connected to source 25. Instead of the rod 31 mirrors can be used. The source 24 and heater 23 can be eliminated, the temperature of region 16 being established by heat leak through partition 18 and lower part of wall 17. An auxiliary heater for the region 15 can be used. The lamp can be used in an optical monitoring system as shown in Fig. 2, the lamp 1 producing a beam of highly resolved, constant intensity optical radiation which is directed through an absorption cell 2 and selectively absorbed by the atomic or other quantum absorbing system contained therein. The cell 2 can contain an alkali vapour in an aligning magnetic field. High signal to noise indications of changes in the alignment of the quanturn system are obtained by the corresponding changes in the intensity of the optical radiation passing through cell 2 without absorption and intercepted by an intensity detector 3. Specification 881,424 is referred to.