Preparation of Cathodes for Use in Demountable Hollow Cathode Lamps

Abstract

The hollow cathode lamp produces intense, stable, and narrow line spectra. Because of these properties, and the fact that it is inexpensive and easy to operate, it is the source of resonance radiation most commonly used in atomic absorption spectroscopy. Most often the lamps used are the sealed type commercially available from various sources. Demountable lamps have been shown, however, to have some advantages when compared to the sealed variety, and are now available commercially. Often water cooling is incorporated into the lamp allowing the lamp to be run at higher currents, thus producing nonreversed lines of greater intensity than can be obtained in sealed lamps. The sealed lamps are only useful for a finite period before they need replacement. In addition, an individual lamp is needed for each element to be analyzed, whereas only the cathode needs replacement in a demountable lamp to change from element to element. The interchangeable cathodes are easily prepared if the material to be excited can be obtained in a machinable form. This is true of many metals, but often cathodes of nonmachinable elements are needed or a machinable piece of the desired material is not readily available. The latter situations are the subject of this correspondence.