Creation of an efficient system for the frequent delivery of cryogenic fuel targets (CFT) to the focus of a powerful laser facility is one of the key directions of research in inertial confinement fusion (ICF). The paper discusses prospects for the creation of a ring magnetic system based on the contactless acceleration of a levitating CFT carrier made of high-temperature type II superconductors (HTSC), up to specified injection velocities of 200–400 m/s. For this purpose, the temperature dependence of the magnetic moment of HTSC tapes in the range Δ T = 10–92 K was studied, prototype experiments on the acceleration of HTSC carriers at T ~ 80 K due to an external action on them with a frequency of ~1 Hz were carried out, and the speed for the stall of HTSC carriers from a circular trajectory were calculated. The calculation results are in good agreement with the experiment, which makes it possible to estimate the parameters of the ring magnetic accelerator for the operating temperature of the CFT injector T ~ 17 K. It is shown that the method proposed is promising for the creation of systems for noncontact delivery of CFT based on the principles of levitation and subsequent injection of CFTs into the center of the ICF reactor chamber at the required speed. The results of planning a new series of experiments are presented: acceleration of an HTSC carrier followed by injection of a surrogate target into the chamber of the GARPUN (LPI) KrF laser.

The mechanism of formation of dome-like phase diagrams and the features of magnetic field penetration in iron pnictides with hetero- and isovalent doping are considered within the framework of the previously proposed model, which assumes the local character of doping and the cluster structure of resulted superconducting phase. It is shown that the proposed model, despite its simplicity and neglect of the features of the electronic structure, makes it possible not only to accurately calculate the positions of superconducting domes on the phase diagrams of specific HTSC compounds, but also to explain the nature and position of sharp peaks in the London penetration depth depending on the doping level.

It is shown that experimentally determined universal scaling relations which relate the critical temperature and superfluid density in cuprate HTSCs under various doping conditions, can be understood within the previously proposed model assuming self-localization of doped carriers.

Earlier we have proposed a new approach to the analysis of superconducting phase diagrams for cuprates and pnictides and have shown that the positions of superconducting domes on the diagrams can be predicted with high accuracy proceeding from only the crystal structure of a particular compound. The proposed approach uses the concept of the self-localization of doped carriers due to their formation of trion complexes that represent a bound state of the doped carrier and charge transfer excitons emerging under its influence. Here, as exemplified by cuprates, we show that the use of the proposed approach to the analysis of the transformation of an electronic structure with doping enables an explanation to a range of their anomalies: Fermi arcs, large and small pseudogaps etc. The basic conclusion is that the role of the Fermi surface in cuprates is played by an isoenergetic contour that emerges at the sectioning of the surface of a band dispersion by a dispersionless biexciton pair level. This level additionally plays the role of an acceptor to lead to the emergence of hole carriers on the isoenergetic contour and to a jump of the chemical potential. Based on the conducted consideration, we propose a possible mechanism of superconducting pairing genetically inherent in such a system.

In this paper, we present a descriptive "electrotechnical" model for calculating the distribution of induction currents in a superconducting film near which a measuring coil inducing a local alternating low-frequency magnetic field is placed. The change in the coil inductance, caused by a superconductor with a set London penetration depth of a magnetic field is calculated within the model. The possibility of determining the penetration depth from experimental data is shown; the sensitivity of the proposed approach for films of various thicknesses and various problem configurations is considered.

This paper reviews experimental phase diagrams of cuprates and pnictides to demonstrate that specific features of the superconducting phase diagrams in both HTSC families can be understood within the framework of the proposed approach, which assumes the formation, under heterovalent doping, of localized trion complexes consisting of a doped carrier and charge transfer (CT) excitons. The geometry of such cells containing CT excitons (CT plaquettes) in the basal plane of the crystal is determined by its crystal structure and the type of dopant, so that the dopant concentration range corresponding to the existence of a percolation cluster of CT plaquettes can be readily determined for each particular compound. These dopant concentration ranges coincide with good accuracy with the experimental ranges of superconducting domes in the phase diagrams of the HTSC compounds considered. The generation of free carriers and the mechanism of superconducting pairing in this pattern is related to biexciton complexes (Heitler-London centers) emerging in neighboring CT plaquettes.

We present our results on utilization of the quantum levitation effect for HTSC samples (superconducting ceramics based on YBa2Cu3O7−x and SuperOx J-PI-12-20Ag-20Cu superconducting tapes) in magnetic fields of different configurations with respect to developing special carriers for hybrid systems of noncontact transport of cryogenic targets in ICF experiments. We implement the obtained results for developing and engineering of “HTSC-MAGLEV” delivery system to minimize the risk for damage of the fuel layer at the target acceleration and during target injection into the center of the ICF reaction chamber.

An approach for the assessment of London penetration depth of superconducting films is proposed. This approach is based on the analysis of linear response of the sample to a local low-frequency alternating magnetic field generated by the measuring coil disposed near the film surface. A visual "electrical engineering" model of induced currents distribution in the superconductor taking into account the kinetic inductance was developed for a description of this response. The possibility of determining of the penetration depth from changing the inductance of the system "coil-sample" is shown in the framework of this model. The sensitivity of the proposed method for the films with different thicknesses is considered.

The influence of 200 keV He+ ion irradiation on superconducting and magnetotransport properties of Ba(Fe0.94Co0.06As)2 films has been studied. It was shown that in the film under the corresponding irradiation conditions, mainly nonmagnetic defects are generated. It was found that suppression of superconductivity at increasing concentration of nonmagnetic defects is noticeably slower than expected from a simple theory assuming s ± symmetry of the superconducting order parameter. The influence of defects on the magnetotransport properties has been analyzed. It was shown that the results of Hall measurements can be explained on the assumption that carriers are localized in the vicinity of radiation defect. The conclusion was made that the complete suppression of superconductivity occurs at a critical disorder in the system, which implies s ++ symmetry of the order parameter. The results are explained basing on the assumption about electron pairing in real space on definite centers of pairing.

It is proposed to use the HTSC quantum levitation phenomenon in magnetic fields of various configurations to develop the systems of contact-free positioning and transport of cryogenic fuel targets (CFTs) to the focus of a high-power laser installation or the IFE reactor. The results are presented of a large cycle of experimental studies using YBa2Cu3O7−x superconducting ceramics and permanent magnet guideways based on various combinations of permanentmagnets to develop “CFT-MAGLEV” delivery systems.

The effect of nonmagnetic defects on superconducting and transport properties of Ba(Fe0.94Co0.06As)2 films is studied for obtaining information on the symmetry type of the order parameter for superconducting pnictides. Such defects are generated in the film by irradiation by He+ ions with an energy of 200 keV. It is found that a decrease in superconducting transition temperature T c upon an increase in the concentration of nonmagnetic defects in this compound occurs much more slowly than predicted in the model assuming s ±-wave symmetry of the order parameter. Joint analysis of the influence of nonmagnetic defects on the superconducting and magnetotransport properties of such films leads to the conclusion that superconductivity is completely suppressed in them after critical disorder is attained, which assumes the s ++-wave symmetry.

The results of experimental studies using SuperOx J-PI-12-20Ag-20Cu tape superconductors in developing capsule carriers for cryogenic systems of noncontact transport of targets for IFE are presented.

The effect of 200-keV He+ ion irradiation on the transport properties of films of the iron-based Ba(Fe1 − x Co x As)2 superconductor has been studied. Contributions to the resistivity and magnetoresistance of irradiated samples from scattering by magnetic and nonmagnetic defects have been separated. It has been shown that mainly nonmagnetic defects are generated in the sample under the corresponding irradiation conditions. This result is important in view of the use of the radiation technique for the study of the effect of defects on the properties of iron-based superconductors.

An advanced technique for contactless study of critical parameters of superconductor materials, based on measurements of the sample nonlinear response to local excitation by an ac magnetic field, is proposed. The results of numerical simulation of the nonlinear response signal spectrum are presented and compared with measurement results. The possibility of reconstructing the superconductor current-voltage characteristic by the response signal shape is considered.

A challenge in inertial fusion energy (IFE) research is to deliver the target to the target chamber center at a high repetition rate. Therefore, the problem of target fabrication and delivery is focused on methods that scale to highly repeatable and cost-effective target production. In this paper, we investigate the possibility of using magnetic-levitation (maglev) transport systems for noncontact manipulation, positioning, and delivery of the cryogenic targets. We focus on the development of transport systems based on movement of high-temperature superconductors (HTSC) over a permanent magnet guideway (PMG). Active guidance is achieved using the HTSC ceramics YBa2Cu3O7− X and PMG, where an ordered motion is initiated by a special arrangement of the permanent magnets. At present, significant R&D programs are ongoing in order to fulfill the technical requirements and basic elements of the system’s operation as a maglev target accelerator. We present here the main results of this work along with recent results.

Conducting media with spatial dispersion may be described formally by the single operator – operator of dielectric permittivity, which, as it is well known, completely defines the microwave response of conductors with spatial dispersion. So the eigenvalue problem for permittivity operator of conductors and superconductors possessing strong spatial dispersion at low temperatures is of a great importance since the corresponding solutions are the stable waves for constitutive equation in a self-consistent microwave field. Here a wave problem is formulated to search the solutions, which correspond to the eigenvalues of permittivity operator, similar to the problem of wave propagation in hollow waveguides and resonators, but non-self conjugated. Dispersion relations and general solutions are obtained. Significant role of the spatial-type force resonances is considered. Conditions for the spatial resonances are derived. The obtained resonances includes particular solutions corresponding to traditional surface impedance for anomalous skin effect, surface impedance of superconductor, as well as four novel solutions, obviously related to polarization, two of which correspond to the waves with amplitude increasing into the depth of conductor, and two else describe solutions with unusual properties.

Earlier, we have proposed [arXiv:1110.0227] the model of HTSC electronic structure modification under doping. In this model, doping by localized charges plays the key role, being responsible for local closing of the gap Δct between excitonic-like 3d10L− state of cation and electronic 3d9L state of anion and formation (at a certain dopant concentration) of the percolation cluster with the Fermi surface located in the cation-anion band of peculiar nature. This electronic structure is favorable for the formation of diatomic negative-U centers (NUCs) and realization of an unusual mechanism of electron–electron interaction. Here, the nature of normal state of cuprates as well as the mechanism of pseudogap and Fermi arcs formation are considered in the framework of this model by example YBCO.

A qualitative model describing the ground state and the mechanism of superconducting pairing in Cu- and Fe-based high-temperature superconductors (HTSCs) is suggested.