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Free keywords:
Physics, Instrumentation and Detectors, physics.ins-det,Nuclear Experiment, nucl-ex, Physics, Atmospheric and Oceanic Physics, physics.ao-ph
Abstract:
After the accident in the Japanese Fukushima Dai-ichi nuclear power plant in
March 2011 large amounts of radioactivity were released and distributed in the
atmosphere. Among them were also radioactive noble gas isotopes which can be
used as tracers to probe global atmospheric circulation models. This work
presents unique measurements of the radionuclide $^{133}$Xe from Fukushima in
the upper troposphere above Germany. The measurements involve air sampling in a
research jet aircraft followed by chromatographic xenon extraction and
ultra-low background gas counting with miniaturized proportional counters. With
this technique a detection limit of the order of 100 $^{133}$Xe atoms in
liter-scale air samples (corresponding to about 100 mBq/m$^3$) is achievable.
Our results proof that the $^{133}$Xe-rich ground level air layer from
Fukushima was lifted up to the tropopause and distributed hemispherically.
Moreover, comparisons with ground level air measurements indicate that the
arrival of the radioactive plume in Germany in high altitude is several days
earlier than on ground.
