High-frequency trigger generators for CuBr-laser high voltage pumping source

In this paper the circuits of high frequency trigger generators of pulses of the nanosecond duration are presented. A detailed study of a generator based on the avalanche transistor with the use of a coaxial cable instead of a capacitor is described. This circuit showed advanced characteristics of the output pulses. A circuit of a generator built on high-speed digital components is also considered. The basic advantages and disadvantages of both generators are presented in this paper

Research of weldability of pipe steel X65 QS ordered for sour service

To evaluate the weldability of steel for sour service the effect of different thermal cycles of welding on toughness and resistance to sulfide stress cracking of the pipe steel X65QS was investigated. Researches were conducted by modeling the welding thermal cycles with heating to a temperature of 1300 °C followed by cooling at different rates. Also kinetics of the austenite decomposition of pipe steel X65 QS in conditions of welding thermal cycles was studied. Dilatometric studies showed bainite transformation in a wide range of cooling rates in GCHAZ. In this case, the main factor affecting both toughness and corrosion resistant is morphology of bainite transformed in GCHAZ. Found that the highest toughness and satisfactory sulfide stress cracking resistance is observed in welded joints with structure of the acicular bainite in the GCHAZ. Acicular bainite in GCHAZ forms at cooling rates 10-20 °C/sec.Для оценки свариваемости стали были проведены исследования влияния различных термических циклов сварки на вязкие свойства и стойкость к сульфидному растрескиванию под напряжением трубной коррозионностойкой стали группы прочности X65QS. Исследования проводили с помощью моделирования термических циклов сварки с нагревом до температуры 1300 °С с последующим охлаждением с различными скоростями. Так же была изучена кинетика распада аустенита стали группы прочности X65 QS в условиях термических циклов сварки. Дилатометрические исследования показали, что в области крупного зерна зоны термического влияния в широком диапазоне скоростей охлаждения присутствует бейнитное превращение. При этом основным фактором, влияющим как на вязкие, так и на коррозионные свойства, является морфология бейнита, сформированного в области крупного зерна зоны термического влияния. Установлено, что самыми высокими вязкими свойствами и удовлетворительной стойкостью к сульфидному растрескиванию под напряжением обладают сварные соединение со структурой игольчатого бейнита в области крупного зерна зоны термического влияния. Игольчатый бейнит в области крупного зерна зоны термического влияния образуется при реализации скоростей охлаждения 10-20 °С/с

Ultrafast manipulation of the NiO antiferromagnetic order via sub gap optical excitation

Wide band gap insulators such as NiO offer the exciting prospect of coherently manipulating electronic correlations with strong optical fields. Contrary to metals where rapid dephasing of optical excitation via electronic processes occurs, the sub gap excitation in charge transfer insulators has been shown to couple to low energy bosonic excitations. However, it is currently unknown if the bosonic dressing field is composed of phonons or magnons. Here we use the prototypical charge transfer insulator NiO to demonstrate that 1.5 eV sub gap optical excitation leads to a renormalised NiO band gap in combination with a significant reduction of the antiferromagnetic order. We employ element specific X ray reflectivity at the FLASH free electron laser to demonstrate the reduction of the upper band edge at the O 1s 2p core valence resonance K edge whereas the antiferromagnetic order is probed via X ray magnetic linear dichroism XMLD at the Ni 2p 3d resonance L2 edge . Comparing the transient XMLD spectral line shape to ground state measurements allows us to extract a spin temperature rise of 65 5 K for time delays longer than 400 fs while at earlier times a non equilibrium spin state is formed. We identify transient mid gap states being formed during the first 200 fs accompanied by a band gap reduction lasting at least up to the maximum measured time delay of 2.4 ps. Electronic structure calculations indicate that magnon excitations significantly contribute to the reduction of the NiO band ga

Megahertz-rate ultrafast X-ray scattering and holographic imaging at the European XFEL

The advent of X-ray free-electron lasers (XFELs) has revolutionized fundamental science, from atomic to condensed matter physics, from chemistry to biology, giving researchers access to X-rays with unprecedented brightness, coherence and pulse duration. All XFEL facilities built until recently provided X-ray pulses at a relatively low repetition rate, with limited data statistics. Here, results from the first megahertz-repetition-rate X-ray scattering experiments at the Spectroscopy and Coherent Scattering (SCS) instrument of the European XFEL are presented. The experimental capabilities that the SCS instrument offers, resulting from the operation at megahertz repetition rates and the availability of the novel DSSC 2D imaging detector, are illustrated. Time-resolved magnetic X-ray scattering and holographic imaging experiments in solid state samples were chosen as representative, providing an ideal test-bed for operation at megahertz rates. Our results are relevant and applicable to any other non-destructive XFEL experiments in the soft X-ray range

Observation of fluctuation-mediated picosecond nucleation of a topological phase

peer reviewedTopological states of matter exhibit fascinating physics combined with an intrinsic stability. A key challenge is the fast creation of topological phases, which requires massive reorientation of charge or spin degrees of freedom. Here we report the picosecond emergence of an extended topological phase that comprises many magnetic skyrmions. The nucleation of this phase, followed in real time via single-shot soft X-ray scattering after infrared laser excitation, is mediated by a transient topological fluctuation state. This state is enabled by the presence of a time-reversal symmetry-breaking perpendicular magnetic field and exists for less than 300 ps. Atomistic simulations indicate that the fluctuation state largely reduces the topological energy barrier and thereby enables the observed rapid and homogeneous nucleation of the skyrmion phase. These observations provide fundamental insights into the nature of topological phase transitions, and suggest a path towards ultrafast topological switching in a wide variety of materials through intermediate fluctuating states. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.Leibniz Association Grant no. K162/2018 (OptiSPIN

Lq-valued Burkholder-Rosenthal inequalities and sharp estimates for stochastic integrals

We prove sharp maximal inequalities for (Formula presented.) -valued stochastic integrals with respect to any Hilbert space-valued local martingale. Our proof relies on new Burkholder–Rosenthal type inequalities for martingales taking values in an (Formula presented.) -space

BIODIAGNOSTICS OF STABILITY OF SOUTHERN RUSSIA CHERNOZEMS STABILITY TO POLLUTION BY HEAVY METALS

By the degree of negative impact on the biological properties of chernozem heavy metals oxides the following series: CrO3 > CuO> PbO> = NiO. Exhibit greater stability ordinary chernozems, lower – typical, even less - the southern, and the smallest – leached fused. Such a sequence is determined by genetic properties of the studied chernozems – the reaction of soil and the organic matter content

IoT monitoring of urban tree ecosystem services: possibilities and challenges

Urban green infrastructure plays an increasingly significant role in sustainable urban development planning as it provides important regulating and cultural ecosystem services. Monitoring of such dynamic and complex systems requires technological solutions which provide easy data collection, processing, and utilization at affordable costs. To meet these challenges a pilot study was conducted using a network of wireless, low cost, and multiparameter monitoring devices, which operate using Internet of Things (IoT) technology, to provide real-time monitoring of regulatory ecosystem services in the form of meaningful indicators for both human health and environmental policies. The pilot study was set in a green area situated in the center of Moscow, which is exposed to the heat island effect as well as high levels of anthropogenic pressure. Sixteen IoT devices were installed on individual trees to monitor their ecophysiological parameters from 1 July to 31 November 2019 with a time resolution of 1.5 h. These parameters were used as input variables to quantify indicators of ecosystem services related to climate, air quality, and water regulation. Our results showed that the average tree in the study area during the investigated period reduced extreme heat by 2 °C via shading, cooled the surrounding area by transferring 2167 ± 181 KWh of incoming solar energy into latent heat, transpired 137 ± 49 mm of water, sequestered 8.61 ± 1.25 kg of atmospheric carbon, and removed 5.3 ± 0.8 kg of particulate matter (PM10). The values of the monitored processes varied spatially and temporally when considering different tree species (up to five to ten times), local environmental conditions, and seasonal weather. Thus, it is important to use real-time monitoring data to deepen understandings of the processes of urban forests. There is a new opportunity of applying IoT technology not only to measure trees functionality through fluxes of water and carbon, but also to establish a smart urban green infrastructure operational system for management