Gallium additive lamp

Spectral outputs of some typical metal halide lamps compared to that of the standard mercury lamp mercury barrier discharge lamp (a) mercury barrier discharge lamp, (b) iron additive lamp, and (c) gallium additive lamp. (Courtesy of American Ultraviolet Company.)... 

Atomic absorption spectroscopy of VPD solutions (VPD-AAS) and instrumental neutron activation analysis (INAA) offer similar detection limits for metallic impurities with silicon substrates. The main advantage of TXRF, compared to VPD-AAS, is its multielement capability AAS is a sequential technique that requires a specific lamp to detect each element. Furthermore, the problem of blank values is of little importance with TXRF because no handling of the analytical solution is involved. On the other hand, adequately sensitive detection of sodium is possible only by using VPD-AAS. INAA is basically a bulk analysis technique, while TXRF is sensitive only to the surface. In addition, TXRF is fast, with an typical analysis time of 1000 s turn-around times for INAA are on the order of weeks. Gallium arsenide surfaces can be analyzed neither by AAS nor by INAA. 

In general, the electrodeless lamp contains a small amount of mercury and a neutral starter gas. The mercury pressures during its operation are in the 5-20 bar range, which is higher than for arc lamps, with pressures only in the 1-2 bar range. The characteristics of fhe lamp can be modified by fhe addition of mefal halides in confrolled quanfifies to the gas. The frequently used D or V lamps contain iron or gallium salts, respectively. Some characteristics of microwave-powered lamps are in Table 3.1. 

The ultraviolet resistance of poly( 1,3,4-oxadiazole) fibers can be improved, by the addition of 4,4 -azodibenzoic acid [50]. The tensile strength retention of the oxadiazole fibers containing 4,4 -azodibenzoic acid is much higher than that of the fibers without the azo groups after accelerated irradiation by an iodine-gallium lamp. Also the fibers with 4,4 -azodibenzoic acid in the molecular chain by copolymerization show a better UV stability than the fibers simply blended with the same amount of 4,4 -azodibenzoic acid. 

Fig. 10.7. High pressure mercury doped metal halide (lead-gallium-iodide additives) UV lamp, type HPM 17, Phillips [2346].

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