Conduction and Breakdown in Hexane

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Abstract
Conduction currents in hexane, studied as a function of spacing, metal, and heat treatment of the electrodes over the field-strength range from 0 to 250 kv/cm, obey neither a field-enhanced thermionic emission nor the customary field emission relation. The most important factor determining the currents appears to be a surface layer on the cathode. Exposing the liquid to gamma rays increases the current in a fashion that indicates a decrease of the effective work function rather than merely a collection of ionization products. Heat treatment of the cathode, by changing the nature of the surface layer, changes the emission. It appears that positive ions collect on the more or less insulating surface layer and build up intense local fields that cause electron emission. The size of the local field depends on the number of the ions arriving per second and on the thickness, homogeneity, and conductivity of the surface layer. For some electrodes the current increases with gap width for constant field; previous investigators have interpreted this fact as evidence of impact ionization in the liquid. However, change of current with gap width proves to be an electrode property; some electrodes do not show it. In one case the current was measured up to breakdown (1060 kv/cm). There is an indication that impact ionization may exist above 800 kv/cm; if so, the ionization factor is very small. A variety of purification systems was tried but no influence of the purification treatment on the conduction currents was found.