The paper describes a high-temperature superconducting magnetic system (HTS SMS) to equip an experimental stand intended for neuron activity researches under constant and low-frequency magnetic fields up to 1 T. The design of the magnetic system together with its electromagnetic and cryogenic parameters is briefly discussed. The test results of the preliminary experiments conducted in liquid nitrogen at 77 K for two interchangeable magnets are given. The first magnet was manufactured in the form of a double pancake coil wound with 4 mm high HTS tape. The second magnet was made of pure copper wire with no frame and was impregnated with a thermally conducting epoxy resin. The advantages of the HTS pancake coil were demonstrated in comparison with the cryo-resistive solenoid. Low energy consumption of the HTS magnetic system will allow conducting continuous non-invasive monitoring of biological objects in a magnetic field.

In this paper, we present the results of the experimental study of the current-carrying capacity for two high-temperature superconducting samples made of either one 12-mm bare REBCO tape or a soldered stack of five such tapes on current growth rates of up to 350 kA/s. For samples in the form of rings with junctions, the transformer method of current injection was used. Experiments at 77 K showed that the currents of thermal equilibrium with the coolant achieved in the samples very weakly depend on the rate of change in the current and are close to critical ones. At 4.2 K, single mechanical defects of the superconducting layer appeared in the samples with a significant decrease in the local critical current. Current charging at different rates were accompanied by local transitions to the normal state caused by Joule heating of the silver coating when the current bypassed a defect with a resistance of ~1 μΩ at 4.2 K. Repeated measurements at 77 K showed that the resistance of these defects increased to 4 μΩ. This resistance determined the achievable currents at low induction voltages in the samples (low rates of current input). However, when passing through 200 kA/s, the currents reached during repeated measurements at 77 K practically equaled the currents of the first measurements at 77 K before the appearance of defects in the samples in liquid helium.

The current-carrying capacity of second-generation commercial high-temperature superconducting REBCO tapes with a width of 12 mm without a stabilizing copper coating (high-temperature superconductor (HTSC) tapes) in liquid helium has been experimentally investigated at current injection rates up to 350 kA/s. In the experiments, tape samples in the form of rings with junctions are placed in the working volume of a superconducting magnet at 4.2 K. The current in the samples is induced by the transformer method. With an increase in the rate of current injection in the ring-shaped samples, single mechanical defects of the superconducting layer appear in the region of junctions, which causes premature transitions of the samples to the normal state. As a result, the maximum attained currents in the ring samples turned out to be up to 50% lower than the critical currents of short HTSC tape samples at 4.2 K. In conclusion, the analysis of the experimental results is given. Possible explanations for the observed effect are given. In addition, the thermomagnetic stability of two single pancake coils comprised of five isolated turns wound from REBCO tapes supplied from different manufacturers is investigated. The jumps in the magnetic flux are not detected up to an external magnetic field variation rate of 1.7 T/s.

The paper describes a high-temperature superconducting magnetic system (HTS SMS) to equip an experimental stand intended for neuron activity researches under constant and low-frequency magnetic fields up to 1 T. The design of the magnetic system together with its electromagnetic and cryogenic parameters is briefly discussed. The test results of the preliminary experiments conducted in liquid nitrogen at 77 K for two interchangeable magnets are given. The first magnet was manufactured in the form of a double pancake coil wound with 4 mm high HTS tape. The second magnet was made of pure copper wire with no frame and was impregnated with a thermally conducting epoxy resin. The advantages of the HTS pancake coil were demonstrated in comparison with the cryo-resistive solenoid. Low energy consumption of the HTS magnetic system will allow conducting continuous non-invasive monitoring of biological objects in a magnetic field.

Экспериментально исследована токонесущая способность коммерческих высокотемпературных сверхпроводящих REBCO-лент второго поколения шириной 12 mm без стабилизирующего медного покрытия (ВТСП лент) в жидком гелии при скоростях ввода тока до 350 kA/s. В экспериментах образцы лент в виде колец со спаями размещались в рабочем объеме сверхпроводящего магнита при 4.2 K. Ток в образцах индуцировался трансформаторным способом. В процессе повышения скорости ввода тока в образцах-кольцах было обнаружено появление одиночных механических дефектов сверхпроводящего слоя в области спаев, вызывающее преждевременные переходы образцов в нормальное состояние. В результате максимально достигнутые токи в образцах-кольцах оказались до 50% ниже критических токов коротких образцов ВТСП лент при 4.2 K. В заключении приводится анализ результатов эксперимента. Даны возможные объяснения наблюдаемого эффекта. Кроме этого, исследована термомагнитная стабильность двух одинарных галет из пяти изолированных витков, намотанных из REBCO-лент разных производителей. Скачки магнитного потока не были обнаружены вплоть до скоростей изменения внешнего магнитного поля 1.7 T/s. Ключевые слова: сверхпроводимость, высокотемпературные сверхпроводники, ВТСП ленты второго поколения, REBCO-ленты, критический ток, термомагнитная стабильность, скачок магнитного потока.

A method is proposed for predicting the life of structural components by analysis of the faults within a short initial operating period.

Разработаны и изготовлены источники магнитного поля для экспериментов по активации каналов нейронов. Разработаны криогенные магнитные системы, входящие в состав экспериментального исследовательского стенда для дистанционного регулирования экспрессии нейронов постоянным и низкочастотным (до 100 Гц) магнитными полями. При температуре жидкого азота (77 К) системы способны выдавать поле с величиной индукции ~0.5 Тл; при работе с переохлажденным жидким азотом (70–65 К) – выше 1 Тл. Подчеркнута актуальность применения в криомагнитной системе новейших и наиболее перспективных материалов на сегодняшний день – высокотемпературных сверхпроводников второго поколения.

High-gradient magnetic separator made a good showing at enrichment of low-magnetic ores. However, existing industrial facilities have large dimensions, low specific productivity and high energy costs. Laboratory prototype of high-gradient magnetic separator equipped with superconductor magnet system was developed, manufactured and tested at NRC “Kurchatov Institute”. The device is designed for enrichment of low-magnetic mineral resources, mostly oxidized ferruginous quartzites. The goal of development was both creation of next-generation of separators operating with high-power magnetic fields as well as further progress in applied superconductivity for industrial applications. This paper gives a brief description of the problem, as well as of the process of development, manufacturing and testing the superconducting magnet system. Overall design of the prototype is described, as well as design of collector matrices designed specifically for high-power magnetic field. Next is description of testing process with mineral raw materials obtained from a real industrial enrichment facility. Data on total iron percentage before and after the separation process at the prototype presented, as well as its basic performance characteristics. The results obtained in the course of the project fulfilment can be used in mining industry and metallurgy for manufacturing superconducting magnetic separators of new generation. Such separators will have many advantages comparing with regular separators (with resistive windings) as following: lower energy consumption and less weight, higher induction of the magnetic field in the working gap, possibility to use matrices with coefficient of filling by ferromagnetic precipitating elements at the level of 6-8% with large gaps for pulp passing, higher specific indices due to increased current density in the winding up to 50-100 A/mm2.

Magnetic field sources are developed and manufactured for experiments in order to activate neuron channels. The designed cryogenic magnetic systems are part of an experimental research stand for remotely controlling neuron expression by static and low-frequency (up to 100 Hz) magnetic fields. The devices are capable of producing an induction field value of ~0.5 T at the liquid nitrogen temperature (77 K); and when working with subcooled liquid nitrogen (70–65 K), the induction field value is above 1 T. The relevance of using the most promising materials—second-generation high temperature superconductors—in the cryomagnetic system is underlined.

The paper gives the results of the experiments with a model two-section REBCO solenoid cooled by either gaseous helium (GHe) or sub-cooled/solid nitrogen (SN2) in (50-77) K temperature range. The major cooling source was a single-stage cryocooler Sumitomo CH-110 with the cooling power of 175 W and 130 W at 77 K and 50 K respectively. The coil itself was not directly conduction cooled. We compare the time taken by both coolants to obtain the temperature of the magnet of about 50 K and the homogeneity of the temperature distribution within the cryostat. Test results for the coil operation in solid nitrogen together with the comparison of its critical properties in SN2 and GHe are also presented.

We propose a new model for pricing quanto credit default swaps (CDS) and risky bonds. The model operates with four stochastic factors, namely: the hazard rate, the foreign exchange rate, the domestic interest rate, and the foreign interest rate, and allows for jumps-at-default in both the foreign exchange rate and the foreign interest rate. Corresponding systems of partial differential equations are derived similar to how this is done by Bielecki et al. [PDE approach to valuation and hedging of credit derivatives, Quantitative Finance 5 (3), 257–270]. A localized version of the Radial Basis Function partition of unity method is used to solve these four-dimensional equations. The results of our numerical experiments qualitatively explain the discrepancies observed in the marked values of CDS spreads traded in domestic and foreign economies.

High gradient magnetic separation is a promising method for ores enrichment and industrial wastes recycling. The potential of separators based on resistive and permanent magnets is limited by the value of magnetic field and operational costs. LTS magnetic systems require liquid helium and complicated cryogenics. HTS magnets operated in solid nitrogen at 50 K can be a possible solution. In this study, we discuss the conceptual design of an HTS rotary separator prototype with the horizontally oriented rotor axis. The scheme allows to organize a continuous ore processing. The split magnet system consists of two 2G HTS coils on a soft-magnetic yoke with 50 mm room temperature gap. The paper gives the overall design of the magnetic system and the related cryogenic, together with the magnetic fields and forces calculations. The preliminary test results of the ReBCO coil in liquid and sub-cooled nitrogen are also presented.

In this paper we present the results of an experimental investigation of single 12 mm REBCO tapes as well as soft-soldered 5-folded REBCO stacks at current ramp rates up to 320 kA/s. Experimental ring-samples made of one or five HTS tapes with joints were manufactured and charged in external magnetic field. The experiments performed at 77 K showed that the current caring capacity of the samples is very weakly affected by transport current ramp rate. No transitions to the normal state were observed in liquid nitrogen at external magnetic field ramp rates up to 8 T/s. The maximum transport currents achieved by the samples were limited by the thermal equilibrium with the coolant. In contrast, at 4.2 K both single and stacked samples demonstrated preliminary quenches caused by the origination of local defects in the superconducting layers of the HTS tapes with resistances of about 1 mu Ohm at 4.2 K. Reexamination of the damaged samples at 77 K showed that at ramp rates higher than 200 kA/s the currents of the thermal equilibrium with the coolant appeared to be the same before and after the defects appearance.

КРИОГЕННЫЕ МЕХАНИЧЕСКИЕ ИСПЫТАНИЯ АУСТЕНИТНЫХ НЕРЖАВЕЮЩИХ СТАЛЕЙ 316L-IG И ЭП302-ША.В.Кривых, А

The international project "NICA" (Nuclotron-based Ion Collider fAcility) is an accelerator complex which is under construction at the Joint Institute for Nuclear Research (Dubna, Russia). Basing on the NICA project demands NRC "Kurchatov Institute" (Moscow, Russia) designed and manufactured two trial 12 kA 1G current leads (CLs) intended for powering of the JINR superconducting magnets test bench. The main requirements for the CLs were: a reliable and robust design, usage of liquid nitrogen from the NICA cooling circuits as a resistive section coolant, low resistance joints, current ramp rates up to 10 kA/s and the total heat load to the 5 K end not exceeding 0.4 W/kA per one CL. An in-situ cold test of the trial 12 kA CLs held at JINR in 2015 demonstrated the operational reliability of our technological approaches. Following the successful test results the serial production of 20 pairs of 10.5 kA HTS CLs with very few design updates for the accelerator powering started. The first 10 pairs were fabricated, tested and shipped to JINR as a part of the NICA commissioning framework in June 2017. All the CLs fulfilled the acceptance test requirements. The production of the remaining 10 pairs is to be finished in 2018. The paper gives an overview of the 12 kA and 10.5 kA HTS CLs' design, discusses their thermal, magnetic and electrical characteristics and presents the acceptance tests results. We also compare our CLs with earlier works by other groups in the context of HTS stack-and-soldering technique, joints' resistances, relative heat loads into the cryogenic environment etc.

High gradient magnetic separation is an effective method for ores enrichment and industrial wastes recycling (including radioactive wastes). The possibilities of separators based on resistive and permanent magnets are limited due to relatively low value of magnetic induction and rather high energy consumption. LTS magnetic systems require liquid helium and complicated cryogenics which can be costly and not always optimal for use at industrial facilities. High-temperature superconductors operated in liquid, sub-cooled and solid nitrogen and equipped with cryocoolers are promising materials that can help expanding industrial application of superconducting devices. In this study, we discuss the design of an HTS rotary separator prototype with the horizontally oriented rotor axis together with the magnetic fields and forces calculations that define prototype working parameters; overall design of HTS-2G coils and preliminary test results of the said coils at different operating temperatures.

In this paper we develop and implement anisotropic radial basis function methods for simulating the dynamics of ice sheets and glaciers. We test the methods on two problems: the well-known benchmark ISMIP-HOM B that corresponds to a glacier size ice and a synthetic ice sheet whose geometry is inspired by the EISMINT benchmark that corresponds to a continental size ice sheet. We illustrate the advantages of the radial basis function methods over a standard finite element method. We also show how the use of anisotropic radial basis functions allows for accurate simulation of the velocities on a large ice sheet, which was not possible with standard isotropic radial basis function methods due to a large aspect ratio between the ice length and the ice thickness. Additionally, we implement a partition of unity method in order to improve the computational efficiency of the radial basis function methods.

A high gradient magnetic (HGM) separator prototype with the 2nd generation high temperature superconducting (2G HTS) magnetic system operated in sub-cooled nitrogen is presently under development at NRC "Kurchatov Institute" (Moscow, Russia). The main goal of the project is an attempt to shift away from the complicated liquid helium cryostats towards simple cryocooler-based nitrogen cryogenics as much more convenient for HGM separators industrial applications. Using of commercial HTS tapes allows to get a sufficient level of magnetic fields and extraction forces with low energy consumption. The expected operational parameters of the device are 1.2-1.5 T in the empty operational gap and up to 3 T on the ferromagnetic filters. In this paper we briefly describe the design of the HTS rotary separator prototype with the horizontally oriented rotor axis and propose different types of ferromagnetic filters intended for weakly magnetic ores enrichment.