| Abstract: | The life time of de-arcs in vacuum was found to be determined by thin film effects on the cathode surface. By removal of surface contaminations in UHV the average arc duration was greatly enhanced. A further enhancement occurs by deposition of clean metal films. This is demonstrated for Mo on Cu-cathodes, and for Cu on Mo-cathodes. Hence compound materials like MoCu show an extreme high arc duration. The vapour pressure of the cathode material, however, has a minor influence. Therefore an arc between MoCu-electrodes emits more Mo- than Cu-vapour, as it is shown by mass analysis. Measurements of dc-field emission from arc cathodes (after the arc) show that the arc life time is correlated to the stability of field electron emission. The most intense field emitting sites are produced during the ignition of the arcs. |
