Untersuchungen zur Zersträubung von Kupfer/Lithium-Legierungen
Untersuchungen zur Zersträubung von Kupfer/Lithium-Legierungen
The sputtering behavior of a copper based alloy containing 17 at-% of lithium has been studied under fusion relevant ion bombardment by D+, He', Ne+, and Ar+ with energies between 0.1 keV and 6 keV and flux densities of up to 10'6 particles/cm2s. The main question was, whether surface segr...
Saved in:
Personal Name(s): | Schorn, Ralph P. (Corresponding author) |
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Contributing Institute: |
Plasmaphysik; IEF-4 |
Imprint: |
Jülich
Forschungszentrum Jülich, Zentralbibliothek, Verlag
1990
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Document Type: |
Report |
Series Title: |
Berichte der Kernforschungsanlage Jülich
Juel-2367 |
Link: |
OpenAccess |
Publikationsportal JuSER |
The sputtering behavior of a copper based alloy containing 17 at-% of lithium has been studied under fusion relevant ion bombardment by D+, He', Ne+, and Ar+ with energies between 0.1 keV and 6 keV and flux densities of up to 10'6 particles/cm2s. The main question was, whether surface segregation of the lithium component can balance the losses due to sputtering and evaporation, and whether this way a protective lithium surface layer can be maintained under high particle flux irradiation. To investigate time-dependent sputtering phenomena, laser-induced fluorescence spectroscopy (LIF) has been employed to detect atoms emitted from the multicomponent material . With LIF, velocity distributions and absolute densities of Cu and Li have been measured, offering the possibility to calculate absolute partial sputtering yields.
At room temperature, the alloy target showed almost no reduction of the Cu sputtering yield under Argon bombardment, compared to pure copper. Under light ion irradiation by D+ and He" reduction factors of up to two have been observed. The surface composition was deduced from measured velocity distributions of the two constituents by assuming a Thompson-distribution and
fitting the resp. surface binding energies, as well as from the reduction factor of the Cu sputtering.
Under Ar+-irradiation, the surface showed the same composition as the bulk, while under bombardment by lighter ions the lithium concentration increased to a maximum of about
50 at-% (D+) in the outmost atomic layer.
A sufficient protective lithium surface layer could be achieved at elevated temperatures above 400°C by heating up the sample for about two hours without ion irradiation. After a subsequent deposition of roughly 10'9 Ar+/cm2 of 6 keV energy, the thickness of the built-up layer has decreased considerably. Losses of lithium atoms due to high-flux sputtering dominate segregation also at elevated temperatures, although the ion dose being necessary to decrease the lithium surface content to its original value has risen by about four orders of magnitude with
respect to room temperature.
The use of the present Cu/Li-material therefore seems useless in a continuously operating fusion reactor. The alloy can only maintain a protective lithium surface layer at elevated temperatures in a pulsed reactor concept, if the plasma is operated with a limited duty-cycle. Moreover, a relatively high rate of lithium evaporation was measured at temperatures above 400°C, which furthermore limits the application of Cu/Li-alloys in fusion devices. |