The COBRA demonstrator at the LNGS underground laboratory Ebert, J.; Fritts, M.; Gehre, D. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
01/2016, Letnik:
807
Journal Article
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The COBRA demonstrator, a prototype for a large-scale experiment searching for neutrinoless double beta-decay, was built at the underground laboratory Laboratori Nazionali del Gran Sasso (LNGS) in ...Italy. It consists of an array of 64 monolithic, calorimetric CdZnTe semiconductor detectors with a coplanar-grid design and a total mass of 380g. It is used to investigate the experimental challenges faced when operating CdZnTe detectors in low-background mode, to identify potential background sources and to show the long-term stability of the detectors. The first data-taking period started in 2011 with a subset of the detectors, while the demonstrator was completed in November 2013. To date, more than 250kgd of data have been collected. This paper describes the technical details of the experimental setup and the hardware components.
The aim of the COBRA experiment is to prove the existence of neutrinoless double-beta-decay (0νββ-decay) and to measure its half-life. For this purpose a detector array made of cadmium-zinc-telluride ...(CdZnTe) semiconductor detectors is operated at the Gran Sasso Underground Laboratory (LNGS) in Italy. This setup is used to investigate the experimental issues of operating CdZnTe detectors in low-background mode and to identify potential background components, whilst additional studies are proceeding in surface laboratories. The experiment currently consists of monolithic, calorimetric detectors of coplanar grid design (CPG detectors). These detectors are 1 × 1 × 1 cm3 and are arranged in 4 × 4 detector layers. Ultimately four layers will be installed by the end of 2013, of which two are currently operating. To date 82.3 kg·days of data have been collected. In the region of interest for 116Cd around 2.8 MeV, the median energy resolution is 1.5% FWHM, and a background level near 1 counts/keV/kg/y has been reached. This paper gives an overview of the current status of the experiment and future perspectives.
Events near the cathode and anode surfaces of a coplanar grid CdZnTe detector are identifiable by means of the interaction depth information encoded in the signal amplitudes. However, the amplitudes ...cannot be used to identify events near the lateral surfaces. In this paper a method is described to identify lateral surface events by means of their pulse shapes. Such identification allows for discrimination of surface alpha particle interactions from more penetrating forms of radiation, which is particularly important for rare event searches. The effectiveness of the presented technique in suppressing backgrounds due to alpha contamination in the search for neutrinoless double beta decay with the COBRA experiment is demonstrated.
This study aimed to investigate the influence of different forms of tissue hypoxia on the expression of the endothelin genes in kidneys and livers. Tissue hypoxia in rats was induced by five ...different manoeuvres, namely hypoxia (8% O2), functional anaemia (0.1% CO), haemorrhage (haematocrit, hct = 0.12), cobalt treatment (60 mg/kg) for 6 h each and renal artery stenosis (0.2-mm clips) for 2 days. Endothelin-1 (ET-1) mRNA levels in the kidneys were increased by 200% with renal artery stenosis, 70% by hypoxia, 50% by anaemia, 30% by CO, but were not changed by cobalt. ET-3 mRNA in the kidneys decreased during renal artery clipping and cobalt treatment and were not significantly changed under the other conditions. ET-2 mRNA was not detected in the kidneys and livers. The abundance of ET-1 in the livers of normoxic animals was about 15% of that found in the kidney. Hypoxia increased ET-1 mRNA by 200%, haemorrhage by 400%, whilst CO and cobalt did not change hepatic ET-1 gene expression. The abundance of ET-3 mRNA in the livers of normoxic animals was about 6% of that found in the kidneys. The expression of the ET-3 gene in the livers was decreased by CO, but was not changed by any of the other experimental conditions used. These findings suggest that hyoxaemia and tissue hypoxia are moderate stimuli for the expression of the ET-1 gene but not for the ET-3 gene in the kidney and more potent stimuli in the liver, whilst cobalt does not activate ET-1 gene expression in the kidneys nor the livers.
T. Gopfert, K. U. Eckardt, B. Gess and A. Kurtz
Physiologisches Institut, Universitat Regensburg, Germany.
This study investigates the effects of hypoxia and of cobalt on
erythropoietin (EPO) gene ...expression in hepatocytes in vivo and in vitro in
neonatal, juvenile, and adult rats. With the use of the ribonuclease
protection assay to quantify RNA, both hypoxia (0.1% CO or 9% O2) and
cobalt (60 mg/kg) elicit production of increased amounts of EPO mRNA in
neonatal and juvenile rat liver in vivo. In vitro hepatocyte EPO gene
expression could be reproducibly stimulated by hypoxia (3% O2) but not by
cobaltous chloride (50-150 microM) within 2-20 h. Conversely, cobalt
substantially attenuated the rise of EPO mRNA levels in response to
hypoxia. This inhibitory effect of cobalt was mimicked by zinc but not by
other metals. CO attenuated the rise of EPO mRNA levels in vitro in
response to hypoxia; this inhibitory effect coincided with an inhibition of
total RNA synthesis as determined by 3Huridine incorporation. The lack of
specific inhibitory effects of CO and of specific stimulatory effects of
cobalt on hepatocyte EPO gene expression in vitro suggests that a specific
heme oxygen sensor may be less important than in hepatoma cells.
Laminin expression was studied in endothelial cells derived from different mouse tissues and primary cultures of bovine aortic endothelium (BAEC). Immunoprecipitation with polyclonal antilaminin‐1 ...revealed two 200‐kDa chains, a novel 400‐kDa chain and nidogen in all cells studied. Two‐dimensional electrophoresis of laminin complexes immunoprecipitated from endothelial‐cell‐conditioned medium demonstrated that the 400‐kDa chain was disulphide‐linked to the laminin β1 and γ1 chains. In addition, rotary shadowing illustrated the secretion of molecules from the endothelial cells which were morphologically similar to laminin‐1. Immunoblotting and Northern blot analysis confirmed the presence of β1 and γ1 polypeptides and the corresponding LamB1 and LamC1 mRNAs in all cells investigated. However, both polyclonal anti‐laminin‐1 and α1‐specific monoclonal antibodies failed to react with the 400‐kDa polypeptide in immunoblots and immunoprecipitations. Similarly, the expression of the gene coding for α1, LamA1, was not detected in the majority of cells by Northern blot analysis using three different cDNAs. Only in two cases, BAEC and a Simian‐virus‐40‐transformed mouse endothelial cell line (SVEC), a 10‐kb mRNA was detected by Northern analysis using a cDNA specific for the 3′ coding region (LAC) of LamA1 mRNA. However, cDNAs specific for the central and 5′ coding region of LamA1 mRNA did not show any reaction. Hybridization of LAC to BAEC and SVEC mRNA is consistant with the laminin‐like nature of the 400‐kDa chain expressed by these cells. The results demonstrate the existence of at least one and possibly two novel 400‐kDa laminin chains which complex with β1 and γ1 and occur in mouse and bovine endothelial cell basement membranes.
Oxygen-Dependent regulation of erythropoietin gene expression in rat hepatocytes. The essential role of the glycoprotein hormone erythropoietin (Epo) in the control of red blood cell production is ...well established. Synthesis of Epo is induced in response to low oxygen (hypoxia). In response to stimulation, increases in serum Epo levels are paralleled by changes in the abundance of Epo mRNA. These changes indicate that the level of Epo mRNA is the major determinant of hormone production rate 1–3. Studies of the organ distribution of Epo mRNA 4, 5 have confirmed the results of organ ablation studies, which demonstrated that in adults the kidney is the major organ responsible for the Epo production, but the liver is capable of Epo production as well 6, 7. More sensitive detection methods of Epo mRNA have demonstrated small quantities in testis, brain, lung, and spleen of rodents 3, 8.
Im Tunnelbau mit Spritzbetonbauweise wird zunehmend das Naßspritzbetonverfahren verwendet. Erhöhte Anforderungen an den Umweltschutz führten zu einer Reduzierung des Alkaligehaltes des Spritzbetons. ...Es wird ein Verfahren zur Herstellung von umweltfreundlichem Spritzbeton vorgestellt, in dem durch gezielte Auswahl des Zements nach seiner chemisch‐mineralogischen Zusammensetzung und durch Zugabe von Aluminat, also nicht alkalifreiem Beschleuniger, das Na2O‐Äquivalent von Zement plus Zusatzmittel auf 1,5 %, bezogen auf das Bindemittel begrenzt ist.
The COBRA demonstrator, a prototype for a large-scale experiment searching for neutrinoless double beta-decay, was built at the underground laboratory Laboratori Nazionali del Gran Sasso (LNGS) in ...Italy. It consists of an array of 64 monolithic, calorimetric CdZnTe semiconductor detectors with a coplanar-grid design and a total mass of 380g. It is used to investigate the experimental challenges faced when operating CdZnTe detectors in low-background mode, to identify potential background sources and to show the long-term stability of the detectors. The first data-taking period started in 2011 with a subset of the detectors, while the demonstrator was completed in November 2013. To date, more than 250kg d of data have been collected. This paper describes technical details of the experimental setup and the hardware components.
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