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.

The mechanism of formation of zirconium nitride-based ceramics in the single-stage high-temperature nitridation of Zr–Nb alloys with different niobium contents (0.1–10 at%) in a wide temperature range was determined using an oxidative constructing approach. In the process of nitridation, the segregation of a metallic niobium phase occurred with the subsequent formation of NbN. This should be taken into account when producing new high-temperature materials with unique functional properties

In this work, we experimentally investigate the current carrying capacity of single REBCO tapes and stacks made 5 12 mm REBCO tapes with a 25 μm copper stabilizer in liquid helium in comparison with those made of bare tapes with no stabilizer at current ramp rates up to 55 kA/s. The motivation for the research was checking the usability of REBCO stacks as basic sub-elements for high current superconducting cables operating in fast cycling modes at 4.2 K. An original experimental technique was employed to induce the extremely high ramp rates. During the tests, one or 5-folded stacks curled into rings 95 mm dia with different types of joints were charged in the external magnetic field generated by an outer solenoid at ramp rates up to 1.6 T/s. The curled REBCO stacks were either soft-soldered over their entire length or contained local joints only. The maximum screening current induced in the samples during the outer solenoid charging I max was registered. Our experiments showed that the current carrying capacity of the REBCO tapes and stacks was strongly affected by the absence or presence of the copper stabilizer as well as the type of the joint. The reasons for the I max limitation for the copper stabilized and bare samples are also briefly discussed.

The article describes the development, fabrication, and test results of a double pancake сoil made using second-generation high-temperature superconductors (HTSC-2G). The HTSC-2G coil is the key element of the cryomagnetic system intended for use as part of an experimental research setup for remotely controlling the expression of neurons by means of constant and low-frequency (up to 100 Hz) magnetic field. This project is a continuation of works [1] carried out on the integrated topic “Electronic Components and Neuromorphic Ccontrol Systems”, which includes, as a constituent part, the development and fabrication of an HTSC-2G cryomagnetic system for studying neuron activity under the effect of external magnetic field. A distinctive feature of the project is the use of a cryomagnetic system with a low energy consumption achieved owing to the use of modern HTSC materials. This will open the possibility to continuously observe the object under study from the start of its exposure to magnetic field to the occurrence of reaction signs. The technology for winding a double pancake HTSC-2G coil is developed and described. For making the coil, an HTSC-2G wire in polyamide varnish insulation was used. The technology of making inner junctions in double pancake HTSC-2G coils with a transition resistance of less than 120 nΩ at 77 K has been developed and successfully tried out. The results from preliminary tests of the HTSC-2G coil in liquid nitrogen are presented.

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.

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.

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.

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.

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.

A new preparation method of bulk hierarchic titania structures for photocatalysis is proposed. A highly porous metallic Ti preform was converted into TiO2 for the first time using a combination of an oxidative construction of thin-wall ceramics (OCTWC) method, intermediate transformation into sodium titanate by hydrothermal treatment in alkaline aqueous solutions and shape preserving removal of sodium by a secondary hydrothermal treatment in acidic aqueous solution yielding a material of rutile/anatase titania with highly developed surface and high photocatalytic activity.

New fusion devices are being discussed in Russia. One item is a superconducting magnet development for the demonstration hybrid facility-fusion neutron source based on a tokamak concept with the conventional aspect ratio ~3. The magnetic parameters of this device are planned to be: 5 Ton the plasma axis and about 12 Ton the high field side of the toroidal field coils. Because of a high neutron flow and a thick shielding, the space remained for the inner legs of the toroidal field coil is very tight. Therefore, a very high current density is needed for the windings. Several magnet designs have been addressed up to now with required engineering critical current density sim 1000 A/mm 2 at least. In this review, we present conceptual design of the magnet system, necessary strand parameters, and their irradiation properties. Few possible designs of the toroidal field, conductors are discussed. The R&D of efficient HTS current leads to be used for fusion machines are discussed as well.

A pair of hybrid current leads (brass + stacked & soldered ReBCO tapes) rated for 12 kA in steady state and for up to 18 kik at pulsed over current conditions was designed, developed and tested at NRC "Kurchatov Institute" (NRC "KI"). During the experiment at LN2 temperature, the current leads (CLs) were successfully charged with 18 kA at 100 A/s ramp rate. To date, as far as we know, this is the highest current capacity achieved for 2G HTS current leads. The feasibility of "stack-and-soldering technique" for 10 kA+ class coated conductor CLs for accelerators and fusion was demonstrated. This paper gives an overview of the leads design and presents the preliminary test results. Detailed studies of magnetic properties and current sharing process for the stacked and staggered HTS joints are also reported. (C) 2017 Elsevier Ltd. All rights reserved.

The feasibility of creating high-current leads on the basis of second-generation (2G) high-temperature superconductors (HTSs) was demonstrated. A method for graded soldering of 2G HTS tape stacks is proposed. It allows one to avoid negative effects that are related to an inhomogeneous current sharing between parallel HTS conductors. A prototype of HTS-coated current leads (CLs) was designed, manufactured, and tested; its critical current exceeds 18 kА. Prototypes of HTS CLs for the superconducting magnetic system of the Nuclotron accelerator (a part of the NICA collider) with an operating current of 6 kA were developed, manufactured, and tested in liquid helium (the overcurrent was 9 kA).

The thermal stability of NbTi Rutherford-type cables was improved with cold spray technology, namely, by depositing high-heat-capacity coatings onto the surface of the superconductors. Two short samples of identical NbTi Rutherford-type cables with different metallic/ceramic coatings were prepared and tested. The spray particles were deposited onto the cables made of eight monofilamentary NbTi/Cu wires via supersonic velocity impact. The temperature of the process is much lower than the melting point of the sprayed material. The doped sample contained 1 vol.% of large-heat-capacity substance (LHCS) Gd 2 O 3 , whereas the comparison sample did not contain any LHCS. The average heat capacity of the doped sample at 4.2 K was increased more than two times. During the tests, both samples at LHe temperature were subjected to short (~1 ms) electromagnetic disturbances in the transverse constant magnetic field. It was found that the minimum quench energies for the sample with Gd 2 O 3 were 1.4-1.5 times higher than that for the comparison cable without LHCS. The described method is very promising for the stabilization of dense massive windings where the direct heat transfer to the LHe is hampered and the superconductor operates in almost adiabatic conditions.

In the case of plasma current interruption in tokamaks, the conductor of toroidial field (TF) coils experiences the action of a pulsed decreasing magnetic field (PDMF) parallel to the conductor’s axis. To estimate the stability of a cable-in-conduit conductor against the PDMF, a new experimental method to study different types of losses is applied. This method exploits a high sensitivity of temperature and gas pressure to input energy in a closed volume. It allows one to measure hysteresis losses with a rather high accuracy (provided that the rate of change of the PDMF is low) and a sum of hysteresis losses and eddy current losses (when the rate of change of the PDMF is high). An experimental setup to measure the transverse (circumferential) resistance and losses has been developed at the National Research Centre Kurchatov Institute. A Russianmade Nb 3 Sn conductor intended for the TF coils of the International Thermonuclear Experimental Reactor is subjected to a PDMF with different amplitudes and characteristic times. The electromagnetic time constant and the transverse resistivity of the conductor are experimentally determined. The maximum temperature of strands under the action of the PDMF is calculated.