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

Production and characterization of a ²²²Rn-emanating stainless steel source

Precise radon measurements are a requirement for various applications,ranging from radiation protection over environmental studies to materialscreening campaigns for rare-event searches. All of them ultimately depend onthe availability of calibration sources with a known and stable radon emanationrate. A new approach to produce clean and dry radon sources by implantation of$^{226}$Ra ions into stainless steel has been investigated. In a proof ofprinciple study, two stainless steel plates have been implanted incollaboration with the ISOLDE facility located at CERN. We present results froma complete characterization of the sources. Each sample provides a radonemanation rate of about 2 Bq, which has been measured using electrostatic radonmonitors as well as miniaturized proportional counters. Additional measurementsusing HPGe and alpha spectrometry as well as measurements of the radonemanation rate at low temperatures were carried out.<br

Highly Sensitive Gamma-Spectrometers of GERDA for Material Screening: Part 2

The previous article about material screening for GERDA points out the importance of strict material screening and selection for radioimpurities as a key to meet the aspired background levels of the GERDA experiment. This is directly done using low-level gamma-spectroscopy. In order to provide sufficient selective power in the mBq/kg range and below, the employed gamma-spectrometers themselves have to meet strict material requirements, and make use of an elaborate shielding system. This article gives an account of the setup of two such spectrometers. Corrado is located in a depth of 15 m w.e. at the MPI-K in Heidelberg (Germany), GeMPI III is situated at the Gran-Sasso underground laboratory at 3500 m w.e. (Italy). The latter one aims at detecting sample activities of the order ~0.01 mBq/kg, which is the current state-of-the-art level. The applied techniques to meet the respective needs are discussed and demonstrated by experimental results.Comment: Featured in: Proceedings of the XIV International Baksan School "Particles and Cosmology" Baksan Valley, Kabardino-Balkaria, Russia, April 16-21,2007. INR RAS, Moscow 2008. ISBN 978-5-94274-055-9, pp. 233-238; (6 pages, 4 figures

Hochempfindlicher Nachweis radioaktiver Edelgasnuklide und natürlicher 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

Detection of 133^{133}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 $^{133}$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 litre-scale air samples (corresponding to about 100 mBq/m$^3$) is achievable. Our results provide 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 at high altitude over Germany occurred several days before the ground level plume.Comment: 8 pages, 5 figure

Characterization of a 220^{220}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 $^{220}$Rn can be used. After being introduced into the xenon, its progeny isotope $^{212}$Pb induces homogeneously distributed, low-energy ($<30$ 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 $^{228}$Th sources with an activity of 55 kBq. These sources provide a high $^{220}$Rn emanation rate of about 9 kBq. We find no indication for the release of the long-lived $^{228}$Th above 1.7 mBq. Though an unexpected $^{222}$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

Indikationen, Komplikationen und Wertigkeit subkutaner Redon-Drainagen bei dermatochirurgischen Eingriffen : Eine retrospektive Studie

Ziel der Arbeit: Neben der Deskription des mit einer Wunddrainage versorgten Patientenkollektivs sollen Indikationen, assoziierte Komplikationen und mögliche Risikofaktoren unter Einsatz von Redon-Drainagen definiert und durch den Vergleich mit einer Patientenkohorte ohne Wunddrainage weiter spezifiziert werden. Methode: Es wurden 495 Patienten, die im Rahmen eines dermatochirurgischen Eingriffs im Zeitraum 01/2010-12/2014 am Universitätsklinikum des Saarlandes mit einem Hoch- oder Niedervakuum-Drainagesystem therapiert wurden, anhand ihrer stationären Akten analysiert. Des Weiteren wurden 155 Patienten, die im gleichen Zeitraum mit vergleichbaren Operationstechniken ohne Drainage behandelt wurden („non-Drainage“-Gruppe), mit 161 Patienten aus der Kohorte der n = 495 Patienten („Drainage“-Gruppe) verglichen. Ergebnisse: Es stellte sich heraus, dass Redon-Drainagen nach einfachen und komplexen Exzisionen und Rekonstruktionen, subkutanen Schweißdrüsenkürettagen sowie nach phlebologischen Eingriffen verwendet wurden. Am häufigsten wurden sie jedoch nach Sentinel-Lymphknoten-Exstirpationen angewendet (321/495; 64,8%). Die Einsatzbereiche variierten dabei in Abhängigkeit von der Vakuumklassifikation des Drainagesystems. Insgesamt kam es in 11,5% der Fälle (57/495) unter Anwendung einer Redon-Drainage zu postoperativen Komplikationen. Hauptsächlich kam es zur oberflächlichen Rötung/Wärme des Wundareals (19/495; 3,8%), zu Schwellungen (15/495; 3,0%), Nachblutungen und Hämatomen (7/495; 1,4%). Seltener kam es zur Lymphfistelung (1/495; 0,2%), zu einem Nervus-interosseus-anterior-Syndrom (1/495; 0,2%), einem Hämoglobin-Abfall oder zur systemischen Manifestation eines Infekts i.S. eines Anstiegs von C-reaktivem-Protein (4/495; 0,8%). In 2,0% (10/495) der Fälle wurde das gleichzeitige Auftreten multipler Komplikationen beobachtet. In 1,6% der Fälle (8/495) kam es zu einer technischen Komplikation des Drainagesystems. Als mögliche Risikofaktoren für erhöhte Komplikationsraten unter Wunddrainage stellten sich das Alter des Patienten, die Antikoagulation und Thrombozytenaggregationshemmung, die Technik sowie die Lokalisation des operativen Eingriffs heraus. Der Vergleich der Patientenkollektive mit und ohne Wunddrainage ergab, dass Redon-Drainagen bei signifikant höherem BMI (p = 0,022), signifikant größerer Defektausdehnung (p < 0,001) und signifikant längerer Operationszeit (p < 0,001) angewendet werden. Die Komplikationsrate mit Drainage (25/161; 15,5%) war im Vergleich zu operativen Eingriffen ohne Drainage (15/155; 9,7%) erhöht (p = 0,118). Dabei traten vor allem Schwellungen unter Wunddrainage häufiger auf (3/155; 1,9% vs. 10/161; 6,2%; p = 0,056). Schlussfolgerungen: Vor dem Hintergrund der konstatierten Ergebnisse der vorliegenden Studie ist der Einsatz von Redon-Drainagen in der Dermatochirurgie tendenziell risikobehaftet. Unter Berücksichtigung der in dieser Studie hervorgebrachten Risikofaktoren bedarf es einer gezielten und individualisierten Indikationsstellung zur Anwendung von Redon-Drainagen in der Dermatochirurgie.Indications, complications and value of subcutaneous Redon drains in dermatological surgery A retrospective study Aim: In addition to the description of the wound drainage group of patients, indications, associated complications and possible risk factors using Redon drainage should be defined and further specified by comparison with a patient cohort without wound drainage. Methods: In this study, 495 patients treated with a high or low vacuum drainage system during a dermatosurgical intervention in the period 01/2010 - 12/2014 were analysed by their stationary files. In addition, 155 patients treated with similar surgical techniques without drainage during the same period (“non-drainage”-group) were compared with 161 patients ("drainage"-group) from the cohort of n = 495 patients. Results: It has been found that Redon drainage is used after simple and complex excisions and reconstructions, sweat gland curettages and after phlebological procedures. However, they are most commonly used after sentinel lymph node exstirpations. The areas of application vary depending on the vacuum classification of the drainage system. Overall, 11,5% of cases (57/495) experienced postoperative complications using Redon drainage. Mainly there was superficial redness/heat of the wound area (19/495; 3,8%), swelling (15/495; 3,0%), rebleeding and hematomas (7/495; 1,4%). In contrast, lymphatic fistulas (1/495; 0,2%), anterior-interosseous-nerve-syndrome (1/495; 0,2%), a decrease in haemoglobin, or a systemic manifestation of an infection within the meaning of an increase of C-reactive protein (4/495; 0,8%) were reported rarely. In 2,0% (10/495) of cases, co-occurrence of multiple complications was observed. In 1,6% of cases (8/495) there was a technical complication of the drainage system. Possible risk factors for increased complication rates under wound drainage were the patient's age, anticoagulation and platelet aggregation inhibition as well as the technique and the location of the surgical intervention. Comparison of patient collectives with and without wound drainage revealed that Redon drainage was applied at significantly higher body mass index (p = 0,022), significantly greater defect size (p < 0,001) and significantly longer operative time (p < 0,001). The complication rate with drainage (25/161; 15,5%) was increased compared to surgery without drainage (15/155; 9,7%) (p = 0,118). In particular, swelling under wound drainage occurred more frequently (3/155; 1,9% vs. 10/161; 6,2%, p = 0,056). Conclusion: Against the backdrop of the findings of the present study, the use of Redon drainage in dermatosurgery tends to be risky. Taking into account the risk factors presented in this study, a targeted and individualized indication for the application of Redon drainage in dermatosurgery is required

Utility of Hounsfield unit in the diagnosis of tandem occlusion in acute ischemic stroke

Background Tandem occlusions can complicate medical and endovascular stroke treatment. To identify these occlusions, computed tomography angiography (CTA) represents the best imaging modality. However, CTA is still not initially performed in some patients not admitted directly to stroke centers. Early identification of an additional occlusion of the proximal extracranial internal carotid artery may improve the best suitable treatment strategy. The purpose of this study was to find a valuable threshold of thrombus attenuation in a non-contrast head CT (NCCT) scan to facilitate a safe diagnosis of tandem occlusions. Materials and methods Consecutive patients with acute middle cerebral artery (MCA) occlusions who underwent endovascular treatment were identified from our registry of neuroendovascular interventions. Thrombus attenuations of the affected MCA and contralateral vessel were measured by NCCT. To compare individual baseline blood attenuations, the difference between the thrombus attenuation and the contralateral MCA attenuation (referred to as ΔTM) was calculated. Results Three hundred and twenty-five patients were included. There was a highly significant difference between mean thrombus attenuation with isolated MCA occlusion and additional extracranial internal carotid artery (ICA) occlusion (49.9 ± 8 vs. 56.2 ± 10 Hounsfield units (HU); P < 0.001). The area under the receiver operating characteristic curve of ΔTM was 0.72. The optimal threshold value was 13.5 HU, with a sensitivity of 67.5% and a specificity of 68.6%. Conclusion Despite a significant difference in thrombus attenuation in MCA occlusions with an additional extracranial ICA occlusion compared with isolated MCA occlusions, a relevant threshold of thrombus attenuation was not found

Highly sensitive gamma-spectrometers of GERDA for material screening: Part I

The GERDA experiment aims to search for the neutrinoless double beta-decay of 76Ge and possibly for other rare processes. The sensitivity of the first phase is envisioned to be more than one order of magnitude better than in previous neutrinoless double beta-decay experiments. This implies that materials with ultra-low radioactive contamination need to be used for the construction of the detector and its shielding. Therefore the requirements on material screening include high-sensitivity low-background detection techniques and long measurement times. In this article, an overview of material-screening laboratories available to the GERDA collaboration is given, with emphasis on the gamma-spectrometry. Additionally, results of an intercomparison of the evaluation accuracy in these laboratories are presented.Comment: Featured in: Proceedings of the XIV International Baksan School "Particles and Cosmology" Baksan Valley, Kabardino-Balkaria, Russia, April 16-21,2007. INR RAS, Moscow 2008. ISBN 978-5-94274-055-9, pp. 228-232; (5 pages, 0 figures