Approaching microwave photon sensitivity with Al Josephson junctions

Here, we experimentally test the applicability of an aluminium Josephson junction of a few micrometers size as a single photon counter in the microwave frequency range. We have measured the switching from the superconducting to the resistive state through the absorption of 10 GHz photons. The dependence of the switching probability on the signal power suggests that the switching is initiated by the simultaneous absorption of three and more photons, with a dark count time above 0.01 s

Ultra-broadband Noise-Insulating Periodic Structures Made of Coupled Helmholtz Resonators

Acoustic metamaterials and phononic crystals represent a promising platform for the development of noise-insulating systems characterized by a low weight and small thickness. Nevertheless, the operational spectral range of these structures is usually quite narrow, limiting their application as substitutions of conventional noise-insulating systems. In this work, the problem is tackled by demonstration of several ways for the improvement of noise-insulating properties of the periodic structures based on coupled Helmholtz resonators. It is shown that tuning of local coupling between the resonators leads to the formation of ultra-broad stop-bands in the transmission spectra. This property is linked to band structures of the equivalent infinitely periodic systems and is discussed in terms of band-gap engineering. The local coupling strength is varied via several means, including introduction of the so-called chirped structures and lossy resonators with porous inserts. The stop-band engineering procedure is supported by genetic algorithm optimization and the numerical calculations are verified by experimental measurements

Investment capacity of the economy during the implementation of projects of public-private partnership

The article considers the peculiarities of the mechanism of public-private partnership. An important problem of the research is to find an optimal ratio in the investment distribution when the arising positive externalities are maximized. In the critical literature review, the assumption was made that the balance between the market and state methods of regulation allows reaching the sustainable growth from the point of view of the use of resources. This hypothesis is developed in the analysis of the multiplicative effect through the index of GDP investment capacity. The research approach is based upon the study of the regression dependencies: multidimensional optimization is solved by the method of configurations with performing the iteration procedure. The obtained results show that the state contribution into the total investment potential of the projects of public-private partnership is traditionally low. The maximal investment capacity of the economy can be reached when maintaining the structure of investment distribution at the ratio 0.09/0.91 for the public and private sectors, respectively. The practical use of the optimization model allows to introduce the flexible mechanism of coordination of the terms of project financing

Efficiency of electron cooling in cold-electron bolometers with traps

Electron on-chip cooling from the base temperature of 300 mK is very important for highly sensitive detectors operating in space due to problems of dilution fridges at low gravity. Electron cooling is also important for ground-based telescopes equipped with 3He cryostats being able to function at any operating angle. This work is aimed at the investigation of electron cooling in the low -temperature range. New samples of cold-electron bolometers with traps and hybrid superconducting/ferromagnetic absorbers have shown a temperature reduction of the electrons in the refrigerator junctions from 300 to 82 mK, from 200 to 33 mK, and from 100 to 25 mK in the idle regime without optical power load. The electron temperature was determined by solving heat balance equa-tions with account of the leakage current, sixth power of temperature in the whole temperature range, and the Andreev current using numerical methods and an automatic fit algorithm

The Mechanical Activation of Crystal and Wooden Sawdust Cellulose in Various Fine-Grinding Mills

Для выбора наиболее эффективного способа механической активации биомассы проведено предварительное исследование процесса измельчения и механической активации образцов кристаллической целлюлозы и лигноцеллюлозной биомассы (высушенные березовые опилки) в мельницах различных конструкций (вальцовая, планетарная, роторная, вихревая газодинамическая и вихревая с механическим разгоном материала) с изучением физико- химических характеристик продуктов помола. Методом рентгенофазового анализа (РФА) проведена идентификация фаз, определены индекс кристалличности (ИК) и средний размер областей когерентного рассеяния, определяющих эффективность активации биомассы. Методом оптической микроскопии исследована морфология и средний размер частиц (l). В качестве наиболее перспективного для последующего более детального изучения выбран метод активации лигноцеллюлозной биомассы в ударной вихревой мельнице с механическим разгоном материала, как обеспечивающий минимальные затраты энергии и времени при удовлетворительной степени измельчения и активации, продемонстрированных для высушенных берёзовых опилок (l ~ 22 мкм и ИК = 56 % при l ~ 3700 мкм и ИК =74 % для исходного сырья)The study is aimed to determine the most perspective and effective fine-grinding mills for lignocellulosic biomass mechanical activation. Physicochemical characteristics were studied for milled crystalline cellulose and milled dry birch sawdust after their treatment in various devices – ball, planetary, ring, vortex gas driven and vortex mechanically driven mills. XRD analysis method was used for phases identification, crystallinity index (CI) and mean size of coherent-scattering region (CSR) measuring. These values are suggested to be used for an assessment of the efficiency of mechanical activation process. Mean particle size (l) of milled materials was measured with help of optic microscopy as well. As the most perspective device for future detailed investigation to be done the vortex mechanically driven mill is selected. This type of mill provides both the least electrical power consumption and activation time at adequate particles destruction level and marked mechanical activation demonstrated for dry birch saw dust (it was detected the reduction of l and CI from l ~ 3700 μm/CI =74 % to l ~ 22 μm/CI = 56 %

Breath air measurement using wide-band frequency tuning IR laser photo-acoustic spectroscopy

The results of measuring of biomarkers in breath air of patients with broncho-pulmonary diseases using wide-band frequency tuning IR laser photo-acoustic spectroscopy and the methods of data mining are presented. We will discuss experimental equipment and various methods of intellectual analysis of the experimental spectra in context of above task

Chaotic Instantons and Ground Quasienergy Splitting in Kicked Double-well System with Time-reversal Symmetry

Chaotic instanton approach was used to describe tunneling properties of the particle in the kicked double well system. Effective Hamiltonian for the kicked system was constructed using matrix expansion for- mula for one period evolution operator exponent. Chaotic instanton approximation was constructed in the framework of the effective model. This approximation was used for estimation of the particle energy range on the chaotic instanton trajectory. Formula for ground quasienergy splitting was obtained aver- aging nonperturbed trajectory action in the obtained energy range in the framework of chaotic instanton approach. Results of numerical calculations for the ground quasienergy splitting dependence on both the perturbation strength and frequency are in good agreement with the derived analytical formula.Для описания характеристик туннелирования частицы в двуямной системе с дельтообразным возмущением был использован метод хаотических инстантонов. Эффективный гамильтониан для данной системы был построен с использованием формулы матричного разложения для оператора эволюции на одном периоде. В рамках эффективной модели была построена аппроксимация хаотического инстантона. Данная аппроксимация была использована для оценки диапазона энергии частицы на траектории хаотического инстантона. В рамках метода хаотических инстантонов выведена формула для расщепления нижних квазиэнергетических уровней путем усреднения действия невозмущенного инстантона в полученном диапазоне. Результаты численных вычислений зависимости расщепления нижних уровней от величины и частоты возмущения находятся в хорошем согласии с полученной аналитической формулой

Numerical modeling of a multi-frequency receiving system based on an array of dipole antennas for LSPE-SWIPE

Here we present the results of a numerical modeling of mode composition in the constriction of the Large Scale Polarization Explorer-Short-Wavelength Instrument for the Polarization Explorer (LSPE-SWIPE) back-to-back horn. These results are used for calculating the frequency response of arrays of planar dipole antennas with cold-electron bolometers for 145, 210, and 240 GHz frequencies. For the main frequency channel (i.e., 145 GHz) we have a 45 GHz bandwidth. For the auxiliary frequency channels (i.e., 210 and 240 GHz) placed on the same substrate, we have bandwidths of 26 and 38 GHz, respectively. We performed some op-timizations for cold-electron bolometers to achieve a photon noise-equivalent power of 1.1 x 10-16 W/Hz1/2. This was achieved by replacing one of two superconductor-insulator-normal tunnel junctions with a superconductor-normal metal contact

Record electron self-cooling in cold-electron bolometers with a hybrid superconductor-ferromagnetic nanoabsorber and traps

The Cosmic Microwave Background (CMB) radiation is the only observable that allows studying the earliest stage of the Universe. Radioastronomy instruments for CMB investigation require low working temperatures around 100 mK to get the necessary sensitivity. On-chip electron cooling of receivers is a pathway for future space missions due to problems of dilution fridges at low gravity. Here, we demonstrate experimentally that in a Cold-Electron Bolometer (CEB) a theoretical limit of electron cooling down to 65 mK from phonon temperature of 300 mK can be reached. It is possible due to effective withdrawing of hot electrons from the tunnel barrier by double stock, special traps and suppression of Andreev Joule heating in hybrid Al/Fe normal nanoabsorber