Abstract:
=========
Grain boundaries of different niobium samples, including cavities samples were
studied systematically by the mean of a nuclear microprobe in order to detect
eventual segregation of tantalum or titanium, but also of light impurities like
carbon and oxygen. This instrument allows to explore small areas (~ 1 µm2)
with a proton or a deuteron beam. Ion Induced X-Ray Emission allows to detect
heavy impurities like Ti or Ta with a good sensitivity, while Nuclear Reactions
can give the signature of oxygen or carbon. The presence at the surface of a
natural oxide layer and a contamination layer gives us access only to
qualitative analysis for these lighter elements. It was although possible to
evidence differences of behaviour between sample originated from different
suppliers, and to show some effects of annealings.
|
