109 research outputs found
Krypton assay in xenon at the ppq level using a gas chromatographic system and mass spectrometer
We have developed a new method to measure krypton traces in xenon at
unprecedented low concentrations. This is a mandatory task for many near-future
low-background particle physics detectors. Our system separates krypton from
xenon using cryogenic gas chromatography. The amount of krypton is then
quantified using a mass spectrometer. We demonstrate that the system has
achieved a detection limit of 8 ppq (parts per quadrillion) and present results
of distilled xenon with krypton concentrations below 1 ppt.Comment: 7 pages, 4 figure
Hochempfindlicher Nachweis radioaktiver Edelgasnuklide und natĂĽrlicher Radionuklide aus der Uran-Zerfallsreihe
Sonnenneutrinoexperimente und andere Experimente, die den Nachweis seltener, niederenergetischer Prozesse zum Ziel haben, benötigen eine Umgebung, die frei von radioaktiver Strahlung ist. Neben primordialen Radionukliden müssen vor allem radioaktive Edelgase effektiv aus den Detektionsmedien entfernt werden. Die Durchführung solcher Experimente erfordert daher effiziente Reinigungsverfahren und hochsensitive Messtechniken. In dieser Arbeit wurden Messverfahren für in der Natur auftretende radioaktive Edelgasnuklide mit Proportionalzählrohren entwickelt. Ein wichtiger Schritt ist dabei die Abtrennung von Verunreinigungen von dem interessierenden Edelgas, die mit chromatographischen Methoden durchgeführt wurde. Die Trennung eines Gasgemisches in einer gepackten Säule beruht auf der unterschiedlich starken Adsorption der einzelnen Gaskomponenten. Um den Trennvorgang zu optimieren, wurde die Adsorption von Gasen an verschiedene Adsorbenzien theoretisch und experimentell untersucht. Die Ergebnisse dienen nicht nur der Entwicklung neuer Messverfahren, sondern sind auch für die Entwicklung von Reinigungsverfahren von Bedeutung. Für das BOREXINO-Experiment wird Stickstoff mit einer sehr niedrigen Kryptonkonzentration benötigt. Daher wurde das Rückhaltevermögen verschiedener Adsorbenzien für Krypton in Stickstoff untersucht. Radionuklide aus den natürlichen Zerfallsreihen primordialer Nuklide sind in praktisch allen Materialienvorhanden. In dieser Arbeit wurde 222Rn und 226Ra in hochreinem Wasser gemessen. Außerdem wurde eine Methode zur Aufkonzentrierung von Radium erarbeitet, die auf der Adsorption an Manganoxid basiert. Sie kann sowohl zum Nachweis wie auch zu Reinigungszwecken verwendet werden. Schließlich wurden erste Schritte zur Entwicklung eines sensitiven Nachweisverfahrens von Uran mittels Beschleunigermassenspektrometrie gemacht, das für das LENS-Projekt von Bedeutung ist
Characterization of a Rn source for low-energy electronic recoil calibration of the XENONnT detector
Low-background liquid xenon detectors are utilized in the investigation of
rare events, including dark matter and neutrinoless double beta decay. For
their calibration, gaseous Rn can be used. After being introduced into
the xenon, its progeny isotope Pb induces homogeneously distributed,
low-energy ( keV) electronic recoil interactions. We report on the
characterization of such a source for use in the XENONnT experiment. It
consists of four commercially available Th sources with an activity of
55 kBq. These sources provide a high Rn emanation rate of about 9 kBq.
We find no indication for the release of the long-lived Th above 1.7
mBq. Though an unexpected Rn emanation rate of about 3.6 mBq is
observed, this source is still in line with the requirements for the XENONnT
experiment.Comment: 8 pages, 5 figure
Detection of Xe from the Fukushima nuclear power plant in the upper troposphere above Germany
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 test global atmospheric circulation models. This work
presents unique measurements of the radionuclide 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 Xe atoms in
litre-scale air samples (corresponding to about 100 mBq/m) is achievable.
Our results provide proof that the 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 at high altitude over Germany occurred several
days before the ground level plume.Comment: 8 pages, 5 figure
Underground gamma-ray measurements of radium isotopes from hydrothermal plumes in the deep Pacific Ocean
© The Author(s), 2019. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Hult, M., Charette, M., Lutter, G., Marissens, G., Henderson, P., Sobiech-Matura, K., & Simgen, H. Underground gamma-ray measurements of radium isotopes from hydrothermal plumes in the deep Pacific Ocean. Applied Radiation and Isotopes, 153, (2019): 108831, doi:10.1016/j.apradiso.2019.108831.The radium isotopes 226Ra and 228Ra can provide important data on the dynamics of deep-sea hydrothermal plumes that travel the oceans for decades and have great impact on the ocean chemistry. This study focuses on parameters important for obtaining low detection limits for 228Ra using gamma-ray spectrometry. It is present at mBq-levels in samples collected during the US GEOTRACES 2013 cruise to the Southeast Pacific Ocean.The work of the HADES-staff of Euridice at SCK•CEN is gratefully acknowledged. We are most grateful to Dr. Faidra Tzika for her work in the precursor to this project. Many thanks to Heiko Stroh for quality control and measurements in HADES. This research was supported in part by grants from the U.S. National Science Foundation, Ocean Sciences division (OCE-1232669 and OCE-1736277)
Muon and Cosmogenic Neutron Detection in Borexino
Borexino, a liquid scintillator detector at LNGS, is designed for the
detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear
reactors, and the Earth. The feeble nature of these signals requires a strong
suppression of backgrounds below a few MeV. Very low intrinsic radiogenic
contamination of all detector components needs to be accompanied by the
efficient identification of muons and of muon-induced backgrounds. Muons
produce unstable nuclei by spallation processes along their trajectory through
the detector whose decays can mimic the expected signals; for isotopes with
half-lives longer than a few seconds, the dead time induced by a muon-related
veto becomes unacceptably long, unless its application can be restricted to a
sub-volume along the muon track. Consequently, not only the identification of
muons with very high efficiency but also a precise reconstruction of their
tracks is of primary importance for the physics program of the experiment. The
Borexino inner detector is surrounded by an outer water-Cherenkov detector that
plays a fundamental role in accomplishing this task. The detector design
principles and their implementation are described. The strategies adopted to
identify muons are reviewed and their efficiency is evaluated. The overall muon
veto efficiency is found to be 99.992% or better. Ad-hoc track reconstruction
algorithms developed are presented. Their performance is tested against muon
events of known direction such as those from the CNGS neutrino beam, test
tracks available from a dedicated External Muon Tracker and cosmic muons whose
angular distribution reflects the local overburden profile. The achieved
angular resolution is 3-5 deg and the lateral resolution is 35-50 cm, depending
on the impact parameter of the crossing muon. The methods implemented to
efficiently tag cosmogenic neutrons are also presented.Comment: 42 pages. 32 figures on 37 files. Uses JINST.cls. 1 auxiliary file
(defines.tex) with TEX macros. submitted to Journal of Instrumentatio
Muon and Cosmogenic Neutron Detection in Borexino
Borexino, a liquid scintillator detector at LNGS, is designed for the
detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear
reactors, and the Earth. The feeble nature of these signals requires a strong
suppression of backgrounds below a few MeV. Very low intrinsic radiogenic
contamination of all detector components needs to be accompanied by the
efficient identification of muons and of muon-induced backgrounds. Muons
produce unstable nuclei by spallation processes along their trajectory through
the detector whose decays can mimic the expected signals; for isotopes with
half-lives longer than a few seconds, the dead time induced by a muon-related
veto becomes unacceptably long, unless its application can be restricted to a
sub-volume along the muon track. Consequently, not only the identification of
muons with very high efficiency but also a precise reconstruction of their
tracks is of primary importance for the physics program of the experiment. The
Borexino inner detector is surrounded by an outer water-Cherenkov detector that
plays a fundamental role in accomplishing this task. The detector design
principles and their implementation are described. The strategies adopted to
identify muons are reviewed and their efficiency is evaluated. The overall muon
veto efficiency is found to be 99.992% or better. Ad-hoc track reconstruction
algorithms developed are presented. Their performance is tested against muon
events of known direction such as those from the CNGS neutrino beam, test
tracks available from a dedicated External Muon Tracker and cosmic muons whose
angular distribution reflects the local overburden profile. The achieved
angular resolution is 3-5 deg and the lateral resolution is 35-50 cm, depending
on the impact parameter of the crossing muon. The methods implemented to
efficiently tag cosmogenic neutrons are also presented.Comment: 42 pages. 32 figures on 37 files. Uses JINST.cls. 1 auxiliary file
(defines.tex) with TEX macros. submitted to Journal of Instrumentatio
Muon and Cosmogenic Neutron Detection in Borexino
Borexino, a liquid scintillator detector at LNGS, is designed for the
detection of neutrinos and antineutrinos from the Sun, supernovae, nuclear
reactors, and the Earth. The feeble nature of these signals requires a strong
suppression of backgrounds below a few MeV. Very low intrinsic radiogenic
contamination of all detector components needs to be accompanied by the
efficient identification of muons and of muon-induced backgrounds. Muons
produce unstable nuclei by spallation processes along their trajectory through
the detector whose decays can mimic the expected signals; for isotopes with
half-lives longer than a few seconds, the dead time induced by a muon-related
veto becomes unacceptably long, unless its application can be restricted to a
sub-volume along the muon track. Consequently, not only the identification of
muons with very high efficiency but also a precise reconstruction of their
tracks is of primary importance for the physics program of the experiment. The
Borexino inner detector is surrounded by an outer water-Cherenkov detector that
plays a fundamental role in accomplishing this task. The detector design
principles and their implementation are described. The strategies adopted to
identify muons are reviewed and their efficiency is evaluated. The overall muon
veto efficiency is found to be 99.992% or better. Ad-hoc track reconstruction
algorithms developed are presented. Their performance is tested against muon
events of known direction such as those from the CNGS neutrino beam, test
tracks available from a dedicated External Muon Tracker and cosmic muons whose
angular distribution reflects the local overburden profile. The achieved
angular resolution is 3-5 deg and the lateral resolution is 35-50 cm, depending
on the impact parameter of the crossing muon. The methods implemented to
efficiently tag cosmogenic neutrons are also presented.Comment: 42 pages. 32 figures on 37 files. Uses JINST.cls. 1 auxiliary file
(defines.tex) with TEX macros. submitted to Journal of Instrumentatio
Borexino calibrations: Hardware, Methods, and Results
Borexino was the first experiment to detect solar neutrinos in real-time in
the sub-MeV region. In order to achieve high precision in the determination of
neutrino rates, the detector design includes an internal and an external
calibration system. This paper describes both calibration systems and the
calibration campaigns that were carried out in the period between 2008 and
2011. We discuss some of the results and show that the calibration procedures
preserved the radiopurity of the scintillator. The calibrations provided a
detailed understanding of the detector response and led to a significant
reduction of the systematic uncertainties in the Borexino measurements
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