Effect of an electric field on superfluid helium scintillation produced by alpha-particle sources

We report a study of the intensity and time dependence of scintillation produced by weak alpha particle sources in superfluid helium in the presence of an electric field (0 - 45 kV/cm) in the temperature range of 0.2 K to 1.1 K at the saturated vapor pressure. Both the prompt and the delayed components of the scintillation exhibit a reduction in intensity with the application of an electric field. The reduction in the intensity of the prompt component is well approximated by a linear dependence on the electric field strength with a reduction of 15% at 45 kV/cm. When analyzed using the Kramers theory of columnar recombination, this electric field dependence leads to the conclusion that roughly 40% of the scintillation results from species formed from atoms originally promoted to excited states and 60% from excimers created by ionization and subsequent recombination with the charges initially having a cylindrical Gaussian distribution about the alpha track of 60 nm radius. The intensity of the delayed component of the scintillation has a stronger dependence on the electric field strength and on temperature. The implications of these data on the mechanisms affecting scintillation in liquid helium are discussed.Comment: 17 pages, 23 figure

Изменения и репрезентативность параметров горного оледенения

The study was aimed at analysis of changes in the area Fgl, the number Ngl and statistical parameters of distribution for different aggregates of glaciers over two periods: 1946–1975 and 1976–2005. The determined changes in the above parameters of glaciers located in river basins of the following mountain regions: the North Caucasus (Baksan, Chegem, Cherek, Malka, Teberda, Terek), Alay ridge (Akbura, Isfara, Isfayram, Shahimardan, Sokh), Altay (Aktru, Chuya, Katun) and Pamir (Gunt), are presented in the article. For better reliability of the height parameters of the glacier aggregates at the scale of the river basins, the maximum, minimum and average height values of individual glaciers were weighed by area. The trustworthiness of changes of the weighed height parameters confirms consistency with the linear relationship adopted at the scale of the river basin between the dimensions of the glaciers and the average weighed heights of beginning, end and average altitude of individual glaciers. Definition of the concept and the scale of representativeness of local measurements of glacier mass balance in the WGMS database is the actual glaciological problem. The proposed quantitative substantiation and the results of the selection of a group of representative glaciers are, in general, based on the use of parameters of dynamical state of individual glaciers distributed over several intervals from the minimum to maximum area values. The parameters of each glacier included: total area, volume, maximum and minimum height difference, index of morphological type, average thickness, orientation and slope of the surface. The sequence of determining the composition of a sample of representative glaciers on the example of glaciations in the basins of the Kyzylsu Western (Pamir) and Katun (Altai) rivers is described. Important part of the work was performed to reveal the possibilities to use local values (Ab – ablation/Bs – summer mass balance) measured on a priori reference/representative glaciers in the WGMS database as an additional argument for modeling and calculation of river runoff at the scale of river basins for June–September and other time intervals. Adding of local values of Ab/Bs as a complementary argument to the regression equations for regional calculations of runoff of the rivers of a snow-glacial feeding in the North Caucasus, Pamir-Alai and Altai was found to be efficient in only limited number of cases. The hydrological representation of the glacier is a new characteristic of practical importance for solving problems of hydrology and glaciology in river basins of snow-glacial type of the flow formation, which include almost all Alpine river basins. The method of revealing the hydrological representativeness of local Ab/Bs measurements described in the paper may be used for glaciers from the existing WGMS network.Описано изменение за 1946–2005 гг. статистических характеристик распределения высотных и площадных параметров для совокупностей ледников на Северном Кавказе, Алайском хребте, в бассейнах рек Катунь (Алтай) и Гунт (Памир). Установлены возможность и обоснованность использования локальных измерений абляции/летнего баланса массы на ледниках Джанкуат (Северный Кавказ), Малый Актру (Алтай) и Абрамова (Памиро-Алай) в качестве дополнительного источника информации при расчётах стока рек снегово-ледникового типа питания

Effect of strain rate on the formation of the microstructure of a 1950/10% SiC metal matrix composite under high temperature

The paper studies the effect of strain rate on the formation of grains and low-angle boundaries in an aluminum matrix composite based on the 1950 alloy (analogous to the AA7075 alloy) with 10 vol% SiC. The deformation of the metal matrix composite, produced by a powder technique, is investigated at a temperature of 500 °C. The specimens are investigated by electron backscatter diffraction before and after deformation at strain rates ranging from 0.1 to 5.5 s-1. It has been established that continuous dynamic recrystallization occurs in the composite at 500 °C in the whole strain rate range considered. The recrystallization is followed by a decrease in the average grain diameter and an increase in the density of the low-angle boundaries with increasing strain rate. © 2017 Author(s).The work was partially financially supported rheological behavior of a metal matrix composite

The environment effect on operation of in-vessel mirrors for plasma diagnostics in fusion devices

First mirrors will be the plasma facing components of optical diagnostic systems in ITER. Mirror surfaces will undergo modification caused by erosion and re-deposition processes [1,2]. As a consequence, the mirror performance may be changed and may deteriorate [3,4]. In the divertor region it may also be obscured by deposition [5-7]. The limited access to in-vessel components of ITER calls for testing the mirror materials in present day devices in order to gather information on the material damage and degradation of the mirror performance, i.e. reflectivity. A dedicated experimental programme, First Mirror Test (FMT), has been initiated at the JET tokamak within the framework Tritium Retention Studies (TRS).Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France).Submitted by B. Schunke on behalf of V. Voytseny

Расчёт и прогноз ледникового питания в речных бассейнах

A two-stage method has been developed for calculating and forecasting the annual volumes of glacial runoff feeding mountainous rivers. At the first stage, the series of morphological characteristics of glaciers are reconstructed using limited data from regional glaciation monitoring. An example of a numerical description and analysis of the annual reconstructed dynamics of glaciation parameters in the upper Rhone River (Switzerland) is presented. Similar results of reconstruction of annual values of the morphological characteristics were obtained for the basins of tributaries of the Terek River (North Caucasus) and the Western Kyzylsu River (Pamir). At the second stage, the calculation and forecast of the time series of the average summer air temperature Ts(Zmean) at the height of Zmean is performed, which is used as an argument for determining the ablation layer by the formula Ab = f(Ts) on the glaciation area Fgl. The annual vertical profiles of mean air temperature of April T4 = T4(Z), summer ones Ts = Ts(Z), and formulas for calculating Ts as a function of T4 are constructed and used for the calculations. Thus, on a regional scale, it was established for the first time that the April air temperature T4 allows calculating a thickness of the annual ablation layer Ab = f(Ts) with a month earliness the forecast at the average height Zmean of the glacier. The reconstructed Fgl(t) series is used to obtain annual volumes of glacial alimentation. A regional study of variability of the index of glacial alimentation δ (Schultz, 1965) with time t was carried out using long-period measurements of runoff in the river basins of Eurasia, North America, Central Europe, and Central Asia. The index δ is equal to the ratio between the volumes W of flow or the average water discharges Q for the periods July-September (Q7–9) and March-June (Q3–6).As a result of the analysis of the expression δ = δ(t), it was found that the gradient of the linear trend equation for the δ index in all the above river basins is negative, which is indicative of a reduction in glacial-snow alimentation, or more precisely – in only its glacial component. Notwithstanding this, the annual runoff Qyear decreased only in three basins, and in the others Qyear, increased due to the growth of Q3–6, which overlapped decreasing of Q7–9. Index δ for the upper reaches of the Rhone River turned out to be not only a representative characteristic of changes in the vegetation period and annual runoff of the river, but also an efficient argument for the super-long-range prediction of these variables for 2025–2054 years.Впервые разработан и проверен метод регионального предсказания с месячной заблаговременностью годовой абляции Ab на высоте фирновой границы Zfg = Zmean как функции прогнозируемой средней летней температуры воздуха Ts. Для определения Ts в начале мая установлены региональные зависимости Ts от температуры воздуха апреля T4. Разработан метод прогноза годового и вегетационного стока р. Рона (Швейцария, Альпы) на 2025–2054 гг

Моделирование и реконструкция параметров речного стока и баланса массы ледников на Северном Кавказе

The work was aimed at numerical modeling of spatial-temporal variability of the river Terek seasonal (April to September) streamflow characteristics and long-term fluctuations of components of annual glacier mass balances in this basin and on the adjacent territories. Mass balance of glaciers Djankuat and Garabashi was calculated. Simulation was performed by means of stochastic modeling and discrete data presenting fields of main meteorological parameters (precipitation, air temperature and humidity) having effect on the streamflow. Realization of this approach is complicated by the fact that spatial representativeness of hydrological and meteorological sites are not corresponding one to another. Data on the runoff is clearly related to the total drainage area closed by a gauging station. And for this data we study a relationship with meteorological parameters which are measured at a non-regular observational network whose spatial representativeness is unknown. These stations are generally located beyond the area under investigation (Fig. 2). Similar problem exists when we analyze a relationship between components of the mass balance of individual glaciers (Djankuat and Garabashi) and the above climate characteristics measured at some stations located on the whole Caucasus territory. The same takes place when long-term indices of width and density of tree annual rings obtained in upper reaches of the river Kuban’ are used for analysis of variations of the runoff and the glacier mass balance in the river Terek basin located at a distance of 100-150 km from the Kuban’ dendrologic sites.To solve the problem we used a wide number of factors which directly (various information about the climate) or indirectly (indices of the climate dryness, wood ring characteristics) characterize conditions of formation of annual and seasonal river runoff and components of glacier mass balance in the North Caucasus. Use of all obtained information made possible the following results: a) new formulas for the calculation of seasonal runoff of the Terek river at the seven gauging stations for 1901–2010 years were derived and verified with independent data; b) significance of various arguments in these formulas was assessed to describe variability of function; c) for the first time relationships between the equilibrium line altitude (ELA), the index of area of accumulation (AAR), and components of the mass balance of the glaciers Djankuat and Garabashi were obtained; d) a technique for regional calculation of average accumulation on these glaciers was developed by using data on ablation and ELA.Для исследования и решения поставленной проблемы использована обширная база факторов прямо (разнообразные сведения о климате) или косвенно (индексы ширины и максимальной плотности древесных колец) характеризующих условия формирования годового и сезонного стока рек и составляющих баланса массы ледников на Северном Кавказе. На основе этой информации получен и проверен на независимых данных ряд новых формул для расчёта сезонного стока р. Терек на семи гидропостах в 1901–2010 гг.; оценена также значимость различных аргументов в этих формулах для описания изменчивости функции. Впервые получены уравнения связи между высотой линии равновесия ELA в конце периода абляции, индексом площади аккумуляции AAR и составляющими годового баланса массы Bn, Bw и Bs на ледниках Джанкуат и Гарабаши. Разработана методика региональных расчётов средних величин аккумуляции на ледниках по данным об абляции и ELA

First test of an enriched 116^{116}CdWO4_4 scintillating bolometer for neutrinoless double-beta-decay searches

For the first time, a cadmium tungstate crystal scintillator enriched in $^{116}$Cd has been succesfully tested as a scintillating bolometer. The measurement was performed above ground at a temperature of 18 mK. The crystal mass was 34.5 g and the enrichment level ~82 %. Despite a substantial pile-up effect due to above-ground operation, the detector demonstrated a high energy resolution (2-7 keV FWHM in 0.2-2.6 MeV $\gamma$ energy range), a powerful particle identification capability and a high level of internal radiopurity. These results prove that cadmium tungstate is an extremely promising detector material for a next-generation neutrinoless double-beta decay bolometric experiment, like that proposed in the CUPID project (CUORE Upgrade with Particle IDentification)