Why we use thoriated tungsten cathodes? COST 529 Eindhoven, 2006.March.31. I.Gaal, L.Bartha

Electron emission micrographs of thoriated tungsten wire Fig.1: As drawn, fibrous state. All others: Recrystallised state All pictures are made at the same surface location. Time sequence: 6-8 sec between each part

Transport of W in halogen lamp 220V/650W halogen studio lamp labelled with W 185 isotope Autoradiogram of filament sections after 10 hours of burning

.. 220V/1000W halogen lamp labelled with Ta 182 annealed 1.) 180V, 2 hours Deposition on surface 2.) 220V, 8 hours Diffusion into the coil 3.)Co 60 annealed 220V Co deposition at the central part, onto the inner side of the coil