Cathode Discharge Source Research Articles

An investigation of the power of detection of the hollow cathode source in emission spectroscopy

In order to experimentally ascertain the detection power afforded by the hollow cathode discharge (HCD) source in emission spectroscopy, various types of samples (solution dry residues, pelletted powders, electrically conducting materials) are analysed adopting in each case those working conditions which permit the signal-to-background ratio to be optimized. In all instances argon at a pressure of a few hundred Pa and current intensities not exceeding 400 mA are used. Spectra are recorded on films and evaluated microdensitometrically. The effects of the specimen's physical state as well as of the simultaneous presence of the other analytes are also elucidated. Detection limits are reported for Ag, Al, As, Bi, Cd, Cr, Cu, Fe, Ga, Mn, Ni, Pb, Se, Sn, Te, Ti and Zn. Experimental data support the view that the said effects are almost negligible. Only in the case of pelletted powders detection limits tend to worsen, this being probably due to the smaller surface subjected to discharge. The possibility of further improving the detection limits of HCD is finally outlined.

Cesiated porous molybdenum converter for intense negative ion sources

Maintaining the proper low work function surface in steady-state high-current-density negative ion sources is difficult, due to intense ion bombardment of the surface. Experiments were performed in which liquid cesium was forced through a porous molybdenum converter in order to obtain a low work function, while at the same time allowing the surface to be cooled. In a small steady-state hollow cathode discharge source, the H− yield from a porous molybdenum converter was five fold higher than from a solid molybdenum converter which relied on the conventional method of cesium coverage by vapor deposition.

SO (B 3σ −,A 3Π—X 3σ −) Emission from low temperature rare gas—sulfur dioxide afterglows

The emission systems produced in He(2 3S)/SO 2, Ne( 3P 0,2)/SO 2 and Ar( 3P 0,2)/SO 2, afterglows have been investigated in the ultraviolet and visible spectral ranges. In all three afterglows we have identified previously unknown long—wavelenght progressions in the SO(A 3Π → X 3 σ −) system and have assigned several new bands in the SO(B 3σ − → X 3σ −)system. Reducing the temperature of the helium gas flowing through a hollow cathode discharge source to 118K effectively removes helium ions from the stream, thus facilitating spectral studies in uncontaminated metastable afterglows. A further effect of cooling the rare gases He, Ne, and Ar is an improvement in the resolution of the emission spectra and an enhanced signal-to-noise ratio. bl