The GERmanium Detector Array (GERDA) experiment searched for the lepton-number-violating neutrinoless double-β (0νββ) decay of ^{76}Ge, whose discovery would have far-reaching implications in ...cosmology and particle physics. By operating bare germanium diodes, enriched in ^{76}Ge, in an active liquid argon shield, GERDA achieved an unprecedently low background index of 5.2×10^{-4} counts/(keV kg yr) in the signal region and met the design goal to collect an exposure of 100 kg yr in a background-free regime. When combined with the result of Phase I, no signal is observed after 127.2 kg yr of total exposure. A limit on the half-life of 0νββ decay in ^{76}Ge is set at T_{1/2}>1.8×10^{26} yr at 90% C.L., which coincides with the sensitivity assuming no signal.
By cyclic gas treatment in ammonia and in air, a composite surface layer with controlled structure may be formed on die steel. Thanks to the catalytic properties of the oxide film that appears, an ...extended multilayer region of chemical compounds is formed at its surface. That improves the erosion and crack resistance of the die steel, with corresponding increase in the life of hot-working dies by a factor of 2–2.5.
Abstract
We consider identical mechanical systems described by Lagrange’s equations of the second kind and subject to the action of positional forces. It is assumed that a separate system allows for ...single-frequency oscillation. The problem of aggregating the set of systems into a coupled system with an attractive cycle close to the oscillation of uncoupled systems is solved. For this purpose, weak universal coupling controls are found.
Neutrinoless double- Formula omitted decay of Formula omittedGe is searched for with germanium detectors where source and detector of the decay are identical. For the success of future experiments it ...is important to increase the mass of the detectors. We report here on the characterization and testing of five prototype detectors manufactured in inverted coaxial (IC) geometry from material enriched to 88% in Formula omittedGe. IC detectors combine the large mass of the traditional semi-coaxial Ge detectors with the superior resolution and pulse shape discrimination power of point contact detectors which exhibited so far much lower mass. Their performance has been found to be satisfactory both when operated in vacuum cryostat and bare in liquid argon within the Gerda setup. The measured resolutions at the Q-value for double- Formula omitted decay of Formula omittedGe ( Formula omitted = 2039 keV) are about 2.1 keV full width at half maximum in vacuum cryostat. After 18 months of operation within the ultra-low background environment of the GERmanium Detector Array (Gerda) experiment and an accumulated exposure of 8.5 kg Formula omittedyear, the background index after analysis cuts is measured to be Formula omitted around Formula omitted. This work confirms the feasibility of IC detectors for the next-generation experiment Legend.
The microstructure, the thickness of the nitrided layer, and the microhardness of a group of corrosion-resistant steels are studied after diffusion saturation in an ammonia-air atmosphere. It is ...shown that the use of such an atmosphere makes it possible to reduce the duration of the process of nitriding by a factor of 3.5 – 4 as compared to nitriding in dissociated ammonia.
The basic science of astronomy and, primarily, its branch responsible for studying the Solar System, face the most important practical task posed by nature and the development of human ...civilization—to study space hazards and to seek methods of counteracting them. In pursuance of the joint Resolution of the Federal Space Agency (Roscosmos) and the RAS (Russian Academy of Sciences) Space Council of June 23, 2010, the RAS Institute of Astronomy in collaboration with other scientific and industrial organizations prepared a draft concept of the federal-level program targeted at creating a system of space hazard detection and counteraction. The main ideas and astronomical content of the concept are considered in this article.
A methodology of experimental simulation of the state of spent nuclear fuel that is situated on the sea bottom as a result of some catastrophes or dumping is developed. Data on long-term (more than ...2000 days) experiments on the estimation of the
85
Kr and
137
Cs release rate from spent nuclear fuel (fragments of irradiated UO
2
pellets) were first obtained; these estimates prove the correctness of the hypothesis put forward by us in the early 1990s concerning an earlier
85
Kr release (by one order of magnitude higher than that of
137
Cs) as compared to other fission fragments in the case of the loss of integrity of a fuel containment as a result of corrosion on the sea bottom. The method and technique of the onboard
85
Kr and
137
Cs sampling and extraction (as well as the sampling of tritium, a product of triple
235
U fission) and their radiometric analysis at coastal laboratories are developed. Priority data on the
85
Kr background in the bottom layers of the Barents and Kara Seas and the
137
Cs and
3
H in these seas (state of 2003) are presented. Models necessary for the estimation of the dilution of the fission products of spent nuclear fuel and their transport on the bottom in accident and dumping regions are developed. An experimental method for the examination of the state of spent nuclear fuel on the sea bottom (1 expedition each 2–3 years) by the
85
Kr release into the environment (a leak tracer) is proposed; this release is an indicator of the destruction of a fuel containment and the release of products of spent nuclear fuel in the case of
235
UO
2
corrosion in sea water.
Consideration was given to an autonomous model with weakly coupled identical subsystems. Existence of a family of periodic solutions which is similar to the family in a subsystem was established. A ...scenario of bifurcations of the characteristic exponents was given, and the stabilization problem was solved. An example was given.
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