Faraday Shield (actively cooled)
To create plasma, the Max Planck Institute for Plasma Physics in Garching uses HF-ion sources. Those are three-walled containers which have an integrated quartz coat and are wrapped with a coil that creates high frequency.
Since the quartz coat is mechanically not stable enough to withstand the inner vacuum, the negative pressure gets adjusted step by step inside the inner walls to normal pressure.
Between plasma and quartz mustn’t be visual contact because the plasma would sputter SiO2 off the coat. This would cast down on other components and disturb the source’s operation. To prevent this a faraday shield is assembled between quartz and plasma.
All in all, this is a complicated design, which makes access to the HF coil (which operates in vacuum) difficult. Therefore, a different design that didn’t have these problems was embraced.
One possible approach turned up during experiments at Galvano-T when Al2O3 ceramics were bonded gas-tight with copper. This allowed for a better design that combined quartz coat (which now became Al2O3 ceramics strips) and faraday shield at a lower wall thickness of 10 mm.
By offsetting bridges and ceramic strips, the Al2O3 is not “visible” to the plasma, protecting it from sputtering. Also, the corpus that gets heated by plasma and HF eddy currents can be cooled completely now with only few additional expenditures.
A prototype, a scaled down model of the ion source, already successfully generated plasma.
The current goal is testing the prototype at real-life conditions until the construction of a 1:1 ion source can be started.
Advantages of galvano-t
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