550 research outputs found
Evaluation of turbulent dissipation rate retrievals from Doppler Cloud Radar
Turbulent dissipation rate retrievals from cloud radar Doppler velocity measurements are evaluated using independent, in situ observations in Arctic stratocumulus clouds. In situ validation data sets of dissipation rate are derived using sonic anemometer measurements from a tethered balloon and high frequency pressure variation observations from a research aircraft, both flown in proximity to stationary, ground-based radars. Modest biases are found among the data sets in particularly low- or high-turbulence regimes, but in general the radar-retrieved values correspond well with the in situ measurements. Root mean square differences are typically a factor of 4-6 relative to any given magnitude of dissipation rate. These differences are no larger than those found when comparing dissipation rates computed from tetheredballoon and meteorological tower-mounted sonic anemometer measurements made at spatial distances of a few hundred meters. Temporal lag analyses suggest that approximately half of the observed differences are due to spatial sampling considerations, such that the anticipated radar-based retrieval uncertainty is on the order of a factor of 2-3. Moreover, radar retrievals are clearly able to capture the vertical dissipation rate structure observed by the in situ sensors, while offering substantially more information on the time variability of turbulence profiles. Together these evaluations indicate that radar-based retrievals can, at a minimum, be used to determine the vertical structure of turbulence in Arctic stratocumulus clouds
Radon and material radiopurity assessment for the NEXT double beta decay experiment
The Neutrino Experiment with a Xenon TPC (NEXT), intended to investigate the
neutrinoless double beta decay using a high-pressure xenon gas TPC filled with
Xe enriched in 136Xe at the Canfranc Underground Laboratory in Spain, requires
ultra-low background conditions demanding an exhaustive control of material
radiopurity and environmental radon levels. An extensive material screening
process is underway for several years based mainly on gamma-ray spectroscopy
using ultra-low background germanium detectors in Canfranc but also on mass
spectrometry techniques like GDMS and ICPMS. Components from shielding,
pressure vessel, electroluminescence and high voltage elements and energy and
tracking readout planes have been analyzed, helping in the final design of the
experiment and in the construction of the background model. The latest
measurements carried out will be presented and the implication on NEXT of their
results will be discussed. The commissioning of the NEW detector, as a first
step towards NEXT, has started in Canfranc; in-situ measurements of airborne
radon levels were taken there to optimize the system for radon mitigation and
will be shown too.Comment: Proceedings of the Low Radioactivity Techniques 2015 workshop
(LRT2015), Seattle, March 201
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