SPECTRAL ANALYSIS SYSTEM INCLUDING HOLLOW CATHODE ELEMENT FOR COMBINED EMISSION OF SPECTRAL RADIATION AND RESONANCE DETECTION

摘要

1,201,005. Glow discharge lamps. WESTINGHOUSE ELECTRIC CORP. 31 Dec., 1968 [10 Jan., 1968; 24 Oct., 1968], No.61906/68. Heading H1D. [Also in Division G1] A single hollow cathode tube is used to provide both radiation emission and resonant detection in atomic absorption spectroscopy. In the arrangement of Fig. 4, the cathode has a two-part bore, the narrow part providing light beam emission, by excitation of sputtered atoms from the cathode, (region 24) and the wider part providing a cloud of ground state atoms in region 25 to act as a resonant radiation detector region. The anode 28 is cylindrical. The support and insulation structure for the electrodes, involving insulating discs, is detailed in Fig. 1 (not shown). In two modifications of this structure, the cathode is made of two parts, one having the narrow bore and the other a wider bore, Fig. 5 (not shown) and the anode separates the two parts of a two-part cathode, Fig. 6 (not shown). In the arrangement of Fig. 7, the anode 130 is off the axis of the tube, the cathode has a uniform bore and an auxiliary annular electrode 150 is used to provide the resonant detection zone. It is of the same material as the cathode and is at a potential more negative than the cathode and thereby forms a cloud of ground state atoms at zone 182. Spacer/screen members 138, 140, 170 of silica, porcelain, alumina &c. are provided. A couple of modifications of this structure are described. In Fig. 8 (not shown), the auxiliary electrode is off-axis. In Fig. 9 (not shown), the auxiliary electrode is heated. Further modifications involve: the use of an insulating sleeve extending from round the cathode, Fig. 10 (not shown); an annular anode, Fig. 11 (not shown); a sequence of spacer discs between cathode and anode, Fig. 12 (not shown); a cathode in the form of a tube, open at both ends, and an anode on the opposite side of the cathode from the radiation emitting end, Fig. 13 (not shown). Cathode materials mentioned are nickel, brass, magnesium; and anode materials, tantalum, nickel, tungsten. The gas filling is neon, argon or helium.