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Weiche Materie Vortrag: Fr., 09:40–10:00 F-V46
Degradation of polyimide (Kapton) induced by irradiation with swift heavy
ions
D. Severin 1 , W. Ensinger 1,2 , C. Trautmann 3 , G. Walter 3 , R. Neumann 3
1 Philipps-University Marburg – 2 Darmstadt University of Technology – 3 Gesellschaft
für Schwerionenforschung, Darmstadt
Polyimide (Kapton) is a highly radiation and thermally resistant polymer. For this
reason, it is one of the preferred insulating materials in technical devices exposed to
high-dose radiation. This not only the case for high-energy photons, but also for swift
heavy ions. The latter might be a problem in the heavy ion synchrotron in the future
ion-beam facility FAIR at GSI, with its very high ion fluxes (10E12 ions/pulse) at high
energies (10 GeV/u). In order to simulate long-term use of Kapton in such devices, foils
were exposed to beams of various ions at ∼10 MeV/u [1]. Ion beam induced material
degradation was investigated by means of UV/Vis-spectroscopy for light transmission,
by IR-spectroscopy for structural degradation, by dielectric spectroscopy for changes
in electrical properties, and by mechanical strength measurements.
It turns out that the data obtained by the different techniques can be scaled by the
total absorbed dose. Up to a dose of about 1 MGy, the material modifications are less
pronounced. However, above this threshold the properties decay significantly. Surprisingly,
the dielectric spectroscopy data do not follow this trend. This method seems
to be sensitive for a different degradation process. The figure shows degradation of
Kapton exposed to beams of various ionic species. The change of the different material
properties is normalized to pristine Kapton. The threshold behaviour, shown by the
different characterization techniques, can well be seen. The underlying physical and
chemical processes, such as bond scission and carbonization, are discussed.
[1] D. Severin, W. Ensinger, R. Neumann, C. Trautmann, G. Walter, I. Alig, S. Dudkin,
Nucl. Instr. and Meth. B 236 (2005) 456-460
Fig. 1: Results of dielectric relaxation, IR,
UV/Vis and tensile strength measuremsnts, of
Kapton foil, as a function of radiation dose