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Home | Rock & Minerals | Photos | De-MA | FIGMAS | Phd (N. Ticino) | MSc (Larecc) |
The glass sample holder is directly connected above the furnace entry. During sample heating in furnace, some gaz are extracted from sample and cleaned by the first getter on the bottom-left (see also previous page). A quantity of gas liberated at a certain temperature represent one "step". After a while, extracted gas is transfered into the purification line. To drive the gas, an active coal trap is used (cooled by liquid nitrogen at -196°C, see figure 2 and 3 below). The valve is then closed and the active coal heated. This liberate the gas in the "cube" and to clean it again with the second getters situated aside. After another gettering time, spectrometer valve is opened and gaz is analysed by spectrometer (see also scheme of extraction line). Gettering time is depending of gas purity. If too much impurities are present (generally at "low" temperature, i.e. 400-700°C), the measurement of argon peaks is perturbed by interferences with other peaks or by an increase of spectrometer background. Generally, the extracted gas of mineral is very dirty during first steps of analysis: impurities situated in cristal network (notably in hydrated phase = "open" structure), fluid or other mineral inclusions... Moreover, hydrated phases are often more dirty and need a longer gettering time up to one hour of gettering. |
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