Abstract

The stability of the dc arc can be increased by the use of a cathode that is cored with a material containing an element of an ionization potential lower than carbon. An effective core material developed for spectrochemical analysis is a 1:2 mixture of BaCO₃ or Li₂CO₃ and graphite powder. In the arc, the added element forms a stationary positive-ion cloud at the tip of the cathode and acts as a ballast to electron flow. Arc temperature is not lowered, as is frequently the case when a buffer is added to the anode. Current and voltage fluctuations and arc wandering are reduced, as indicated by recordings during sample consumption. Several hundred sample materials have been tested to determine the usefulness of the cored cathode.

Effect of Alkali and Alkaline Earth Chlorides on the Anode Temperature of the dc Arc*

Bert L. Vallee and Ralph E. Thiers
J. Opt. Soc. Am. 46(2) 83-86 (1956)

Anode Temperatures and Characteristics of the dc Arc in Noble Gases*†

Bert L. Vallee and Milton R. Baker
J. Opt. Soc. Am. 46(2) 77-82 (1956)

Spectroscopic Estimation of dc Arc Electrode Vapor-Jet Velocities*

Stanley C. Baker
J. Opt. Soc. Am. 54(10) 1204-1210 (1964)

Note on Bräuer’s Theory of the Function of the Cathode in Electric Arcs

A. Trowbridge and K. T. Compton
J. Opt. Soc. Am. 7(4) 321-325 (1923)

Continuous calibration of a vacuum ultraviolet system from 65 to 125 nm by a cascade arc and comparison with the calibrated line radiation of a hollow cathode

Robert Martin Frost and Peter Awakowicz
Appl. Opt. 36(9) 1994-2000 (1997)