Boosted hollow-cathode lamp

The boosted hollow-cathode lamp A very intense radiation source for AAS is the boosted hollow-cathode lamp. It has been developed from the regular hollow[Pg.438]

Collection optics Boosted hollow-cathode lamp (light source)... 

Atomic Fluorescence System - Millennium Excalibur PSA 10.055 -was used in our work. This system consists of the autosampler, the integrated continuous flow vapour generator and the atomic fluorescence spectrometer with the boosted dischar ge hollow cathode lamp and a control computer. 

By far the most common lamps used in AAS emit narrow-line spectra of the element of interest. They are the hollow-cathode lamp (HCL) and the electrodeless discharge lamp (EDL). The HCL is a bright and stable line emission source commercially available for most elements. However, for some volatile elements such as As, Hg and Se, where low emission intensity and short lamp lifetimes are commonplace, EDLs are used. Boosted HCLs aimed at increasing the output from the HCL are also commercially available. Emerging alternative sources, such as diode lasers [1] or the combination of a high-intensity source emitting a continuum (a xenon short-arc lamp) and a high-resolution spectrometer with a multichannel detector [2], are also of interest. 

Brief mention should also be made here of high intensity (also known as boosted output ) hollow cathode lamps.7 In these lamps an auxiliary current of around 200-400 mA is applied to the dilute cloud of atoms sputtered outside the central zone of the normal hollow cathode. The atoms are thus excited and emit intense radiation which may be used in AAS or AFS. Once again an auxiliary power supply is required, and the lamps themselves are more complex and correspondingly more expensive. Such lamps have had a rather chequered history, finding great favour in some environmental analytical laboratories but never being widely used on any routine basis. 

While conventional or high-intensity (boosted output)4 hollow cathode lamps are usually simply operated at room temperature, electrodeless discharge lamps are sometimes cooled with a regulated flow of air maintained at a constant temperature,5 and this flow too must be optimized with respect to signal-to-noise ratio. Sometimes these sources are operated in a vacuum jacket to enhance sensitivity and/or to improve stability.6... 

Technical modification of the Grimm lamp (a hollow-cathode lamp operating in the microwave-boosted mode) has given increased sensitivity compared to the conventional hollow-cathode lamp [1041. Argon line interferences have been removed by introducing a third electrode to modulate the intensities (lO. )). A low-pressure device can be introduced in order to decrease atmospheric contamination of the sample [106]. Fa.st Fourier transform analysis of emitted light has provided increased sensitivity (e.g.. Mo in steel down to 50 ppm [I07 ). 

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