Cooled ferromagnetic shield as a part hybrid system for isolation of a flux qubit from electromagnetic environment

Currently, circuits for quantum informatics, communications and measuring equipment containing superconducting flux qubits in a planar design are being created by quantum engineering techniques. To function, such structures must be cooled in a refrigerator down to about 10 mK. The flux qubits have linear size of superconducting circuit of some tens of micrometers and are very sensitive to external magnetic fields and their variations.  The qubit built in the gradiometer-like design has reduced sensitivity to external uniform magnetic fields, but remains quite sensitive to their variations. To protect the qubit from unwanted external magnetic fields, which include the Earth's field, man-made fields, and residual magnetic fields of the cryostat parts, it is necessary to create efficient magnetic shields. Earlier, we proposed a scheme for a single-photon microwave counter, in which a planar flux qubit in a gradiometer version serves as the receiving element. To let it function properly, a 3-layer hybrid magnetic shield composed of two superconducting and one ferromagnetic cylinders, has been designed for installation in a dilution refrigerator at 10 mK temperature. The effectiveness of such a shield depends on the correct design of all three shells. This paper presents the results of calculation and magnetic measurements of a cylindrical ferromagnetic screen made of low-temperature permalloy Cryoperm 10 in dc and low-frequency alternating magnetic fields. Cryoperm 10 keeps high magnetic permeability at liquid helium temperatures and below. It is shown that this shield is able of reducing the absolute value of the magnetic field and its variations by 55-70 dB. Together with superconducting lead magnetic shields, this design will reduce the absolute value of the field by 70 dB, and the field variation by 200 dB, which will provide the necessary conditions for the operation of a single-photon counter based on a flux qubit

Structure and optical properties of AlN films obtained using the cathodic arc plasma deposition technique

Aluminum nitride (AlN) film coatings have been obtained by a new technique of hybrid helikon-arc ion-plasma deposition. Possibility to combine the magnetic-filtered arc plasma deposition technique with a treatment in RF plasma of helicon discharge allowed us to deposit AlN coatings on thermolabile substrates, significantly increasing the deposition rate. A study of spectral properties of AlN films (reflection and transmission spectra within the range 2…25 µm) has been carried out by using the infrared Fourier spectrometer Spectrum BX-II. It has been shown that the obtained composite structures (AlN coatings on teflon and mylar substrates) could be used as passive filters in the infrared spectral range

Current status of turbulent dynamo theory: From large-scale to small-scale dynamos

Several recent advances in turbulent dynamo theory are reviewed. High resolution simulations of small-scale and large-scale dynamo action in periodic domains are compared with each other and contrasted with similar results at low magnetic Prandtl numbers. It is argued that all the different cases show similarities at intermediate length scales. On the other hand, in the presence of helicity of the turbulence, power develops on large scales, which is not present in non-helical small-scale turbulent dynamos. At small length scales, differences occur in connection with the dissipation cutoff scales associated with the respective value of the magnetic Prandtl number. These differences are found to be independent of whether or not there is large-scale dynamo action. However, large-scale dynamos in homogeneous systems are shown to suffer from resistive slow-down even at intermediate length scales. The results from simulations are connected to mean field theory and its applications. Recent work on helicity fluxes to alleviate large-scale dynamo quenching, shear dynamos, nonlocal effects and magnetic structures from strong density stratification are highlighted. Several insights which arise from analytic considerations of small-scale dynamos are discussed.Comment: 36 pages, 11 figures, Spa. Sci. Rev., submitted to the special issue "Magnetism in the Universe" (ed. A. Balogh

Features of rat skin structure in norm and at pyrogenalum action

On 48 rats-males of genesial age in mass 140-210, which have been parted on four groups: 1 group – control; 2, 3, 4 groups – experimental (entered Pyrogenalum in a dose of 3,0 mg/kg once a day throughout the days two and three accordingly) features of a structure of a skin in norm have been studied and at Pyrogenalum introduction. The microscopic sections of a skin received in two is mutual perpendicular planes, dyed by hematoxylin-eosin and Mallory-Slinchenko's method. The obtained quantitative data processed with use of methods of variation statistics. After intraperitoneal introduction of Pyrogenalum in a dose of 3,0 mg / kg of change of a structure of a skin occur in all регионально various sites. They consist in augmentation of a thickness of separate layers of a skin, augmentation of diameter of lead-out ducts потовых glands, edemas of tissues, reduction of density of collagen fibers. To the greatest changes at a hyperthermia a vascular bed of a skin which are most expressed at early o'clock after Pyrogenalum introduction. At secondary introductions of Pyrogenalum of rasping changes in a skin does not occur and for 7 8 days the skin structure is similar to a skin of control group of animals

Выбор оптимальных режимов тепловой обработки как подготовительного этапа перед огнезащитой древесины

Для якісного просочування деревини вогнезахисними засобами проводять попереднє її теплове оброблення. У цьому дослідженні використано такий вид оброблення, як пропарювання. Дуже важливо, щоб під час попереднього приготування дерев'яних заготовок до вогнезахисту, не втратити природних позитивних якостей деревини. Визначено вплив теплового оброблення на динаміку зміни фізико-механічних властивостей деревини. Внаслідок експериментальних досліджень вибрано оптимальні режими пропарювання, які зберігають якісні фізико-механічні показники, такі як: запобігання втратам деревини під час зберігання та транспортування, вирівнювання забарвлення або надання деревині потрібного кольору, покращення міцності і пластичності, пришвидшення подальшого сушіння.For high-quality impregnation of wood by flame retardant means it is pre-heat treated. In this case we use this type of finishing, like steaming. It is very important not to lose the positive qualities of natural wood during the preliminary preparation of the wood for the fire protection. The conducted research allowed to determine the influence of heat treatment on the dynamics of changes in physico-mechanical properties of wood. As a result of experimental studies of the selected optimal modes of curing that maintain high-quality physical and mechanical properties, such as the prevention of timber losses during storage and transportation, alignment, color, or giving the wood the desired color, the improvement of strength and plasticity, accelerate subsequent drying.Для качественного просачивания древесины огнезащитными средствами проведена предварительная ее тепловая обработка. В этом исследовании использован такой вид обработки, как пропаривание. Очень важно, чтобы во время предварительного приготовления деревянных заготовок для огнезащиты, не потерять естественных положительных качеств древесины. Определено влияние тепловой обработки на динамику изменения физико-механических качеств древесины. В результате экспериментальных исследований выбраны оптимальные режимы пропаривания, которые сохраняют качественные физико-механические показатели, такие как: предотвращение потерь древесины при сбережении и транспортировании, выравнивание окраски или предоставление древесине необходимого цвета, улучшение прочности и пластичности, ускорение последующей сушки

Метод вимірювання діелектричної проникності та тангенса діелектричних втрат мікропорошків в широкому діапазоні частот

Діелектричні та магнітні мікропорошки знайшли своє призначення у широкому спектрі науковотехнічних задач. Наприклад, мікропорошки застосовують як основу поглинаючих мікрохвильових покриттів для зменшення відбиття хвилі в антирадарних системах. У надсучасних квантових обчислювальних схемах і детекторах з наднизьким рівнем шуму, мікропорошки використовуються як наповнювачі коаксіальних термоблокуючих фільтрів. Такі фільтри вкрай необхідні для забезпечення шумової ізоляції глибоко охолоджених пристроїв від вимірювальної апаратури, яка знаходиться при кімнатній температурі. Для розрахунків пристроїв на основі мікропорошків необхідно отримати їх діелектричні та магнітні характеристики. Для цього на низьких частотах використовують конденсаторні або індуктивні методи, а на мікрохвильових частотах – хвилеводні методи. В роботі запропоновано метод визначення діелектричних та магнітних характеристик мікропорошків для покриття проміжного діапазону метрових та сантиметрових довжин хвиль. Метод базується на вимірюванні частотних залежностей втрат та зміни фази сигналу, що проходить скрізь відрізок коаксіальної лінії передачі з мікропорошковим наповненням. З використанням запропонованого метода проведені дослідження мікропорошків з оксиду графену, графіту та карбонільного заліза та знайдені значення їх діелектричних/магнітних проникностей та тангенсів втрат в діапазоні частот 300 кГц – 26.5 ГГц. Приведено структурний аналіз форми та розмірів зерен мікропорошків. Зроблені розрахунки визначення достовірного частотного діапазону для вимірювання діелектричних/магнітних параметрів досліджених мікропорошків, та проведено оцінку чутливості запропонованої методики.Dielectric and magnetic powders find their use in a wide spectrum of scientific and technical tasks. For example, micropowders are used as a base of microwave absorbing coverage for the reflection reduction of the electromagnetic waves in the anti-radar systems. In the modern quantum computing and ultra-low noise detectors, they are used as a filling of the coaxial thermal blocking filters. Such filters are extremely necessary to ensure the noise shielding of deeply cooled devices from the measurement equipment under room temperature. For correct calculations of devices based on micropowders, it is essential to obtain their dielectric and magnetic properties. For this reason, parallel plates and induction techniques are used in the low-frequency range, and waveguide methods are used in the HF and SHF ranges. An experimental method for determining the dielectric and magnetic properties of micropowders that covers the meter to centimeter range is proposed. The main idea is to measure frequency dependences of losses and phase changes of the signal transmitted through a coaxial line segment with powder filling. Using the stated technique, we perform the measurements of graphene oxide, graphite and carbonyl iron micropowders, and the values of relative permittivity/permeability and loss tangent in the range 300 kHz – 26.5 GHz are obtained. The structural analysis of the shape and dimensions of micropowders grains is given. Determination of a reliable frequency range for measuring the dielectric/magnetic parameters of investigated micropowders is obtained, and the sensitivity of the offered technique is estimated

Dissipation effects in superconducting heterostructures with tungsten nanorods as weak links

Thin-film hybrid heterostructures formed by superconducting molybdenum-rhenium-alloy films with a critical temperature of about 9 K and nanoscale silicon-based semiconducting interlayers with metallic tungsten nanorods have been fabricated and studied. Current-voltage characteristics of the junctions were measured at 4.2 K and under influence of 11 GHz microwave irradiation. The evidence of a quasi-one-dimensional transport through the tungsten weak links disrupted by phase-slip centers was revealed in MoRe/doped Si/MoRe trilayers under irradiation by a high-frequency field. Also, measured current-voltage characteristics of five-layer MoRe/doped Si/MoRe/doped Si/MoRe devices exhibit a strong influence of a dissipation state in the MoRe interlayer. Namely, the switching from a superconducting state with low dissipation to a finite-conductance regime can be initiated by the emergence of an extra phase-slip center in the MoRe interlayer. Possible physical mechanisms of the two findings are discussed

3D-printed microfluidic system for the in situ diagnostics and screening of nanoparticles synthesis parameters

Fine tuning of the material properties requires many trials and errors during the synthesis. The metal nanoparticles undergo several stages of reduction, clustering, coalescence and growth upon their formation. Resulting properties of the colloidal solution thus depend on the concentrations of the reagents, external temperature, synthesis protocol and qualification of the researcher determines the reproducibility and quality. Automatized flow systems overcome the difficulties inherent for the conventional batch approaches. Microfluidic systems represent a good alternative for the high throughput data collection. The recent advances in 3D-printing made complex topologies in microfluidic devices cheaper and easily customizable. However, channels of the cured photopolymer resin attract metal ions upon synthesis and create crystallization centers. In our work we present 3D-printed system for the noble metal nanoparticle synthesis in slugs. Alternating flows of oil and aqueous reaction mixtures prevent metal deposition on the channel walls. Elongated droplets are convenient for optical and X-ray diagnostics using conventional methods. We demonstrate the work of the system using Ag nanoparticles synthesis for machine-learning assisted tuning of the plasmon resonance frequency