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![[Figure 3]](ok5025fig3mag.jpg)
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Figure 3
Example of a typical heating process of a niobium metal foil with a well controlled N2 gas exposure in the process chamber, comparable with heat treatments of Nb cavities for accelerating structures. (a) Evolution of the time–temperature program. At t = 1200 s, a heating ramp to T = 900°C was initiated, the temperature was then held for ∼3000 s, until the heater was switched off at t = 4150 s. In the inset, the fit of the temperature increase yields a heating rate of ∼350°C min−1 (dashed black line). (b) Evolution of the vacuum conditions during the heat treatment in (a). After initiating the heating process, the base pressure of ∼2.2 × 10−6 mbar slightly increases during the heat treatment. At t = 2600 s, an N2 exposure at 1.5 × 10−3 mbar was initiated for ∼1200 s. At t = 3800 s, the N2 exposure was terminated, and the base pressure of the cell (p ≃ 1.2 × 10−6 mbar) quickly recovered after switching off the heater at t = 4150 s. |
![[Figure 3]](ok5025fig3.jpg)
 | JOURNAL OF SYNCHROTRON RADIATION |
ISSN: 1600-5775
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