| | - R. Eichhorn, A. Araz, M. Brunken, J. Conrad, H. D. Graef, M. Hertling, F. Hug, M. Konrad, T. Kuerzeder, M. Platz, A. Richter, S. Sievers, T. Weilbach
TU-Darmstadt S-DALINAC
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| | Reaching the design quality factors and lowering the
residual losses of the cavities at the superconducting
electron linac in Darmstadt (S-DALINAC) is still an
ongoing activity. After installation of an UHV furnace in
Darmstadt two years ago, six cavities have now been heat
treated at 850 C to remove residual hydrogen from the
niobium cavity surface. A gas analysis during the heat
treatment procedure showed that the cavities were
strongly contaminated which might explain the low Q. We
will report about the furnace, the heat treatment procedure
and the results of subsequent surface resistance
measurements. Prior to the heat treatment the field
flatness of the 20 cell elliptical cavities was measured
leading to unexpected results: After almost 10 years of
operation, the field flatness of some cavities was heavily
distorted. This might be an indication that the frequency
tuning of the cavity, which is done by compressing the
cavity longitudinally, does not act uniformly on each cell
even though the cavity is only supported at the end cells. | |