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Laser-based X-ray sources like laser-induced plasma (LIP) established as laboratory scale EUV- and soft X-radiation
sources in many scientific fields. Concerning the relative low conversion efficiencies of about 0.5% to 1% one has to
avoid scattered laser light reaching the X-ray optical setup. For this, thin metal filters with a thickness of a few hundred
nanometres are used. Another purpose of the filter is to block high-speed ions, clusters and particles (debris) originating
from the plasma, thus protecting the X-ray optics against damage. This is especially true when solid targets are used for
plasma generation.
Concerning the application of LIP sources, one needs to collect as much radiation as possible. Therefore X-ray optics
with a high numerical aperture are required and the shielding filter has to be large and far-off the source or vice versa.
Since large thin filters are very fragile, one has to find a compromise between these two parameters to achieve
appropriate filter lifetime.
In this work we describe the stage of experiments to learn more about the process of debris emission characteristics and
the risk of damage to sensitive filters and X-ray optics. The experiments were carried out at a LIP source using a liquid
nitrogen jet or an ethanol jet as target. Several types of metal foils are investigated at different distances to the source.
Each filter is imaged onto a CMOS-Camera to examine the leakage of scattered laser light by debris-generated pinholes.
The analysis of the experiments is carried out particularly with regard to the theoretical X-ray throughput versus lifetime
of the different filter types.
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