Why we use thoriated tungsten cathodes?

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Why we use thoriated tungsten cathodes?

• COST 529
• Eindhoven, 2006.March.31.
• I.Gaal, L.Bartha

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• 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

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Transport of W in halogen lamp

• 220V/650W halogen studio lamp labelled with W185
  isotope
• Autoradiogram of filament sections after 10 hours
  of burning

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• 220V/1000W halogen lamp labelled with Ta182
  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

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