Center Conductor Research Articles

Strain analysis by neutron diffraction on Nb3Sn strands in ITER central solenoid conductors of short and long twist pitch

Abstract The ITER central solenoid (CS) conductors are composed of Nb3Sn superconducting cables and stainless steel jackets. Approximately 60 000 electromagnetic loading cycles will be applied to the Nb3Sn strands in the CS conductor over the course of ITER tokamak operation, and the CS conductor is required to maintain the current sharing temperature (T cs) for these electromagnetic loading cycles. However, in CS conductor prototypes, degradation of T cs was observed after electromagnetic loading cycles. Visual inspections of the tested CS conductors revealed large bending and buckling of the Nb3Sn strands. These strand deformations were considered to be the cause of T cs degradation because even a small amount of strain markedly affects the critical current of Nb3Sn strands. To prevent the strands from bending and buckling, the twist pitch of the cable was shortened to improve stiffness. The stiffer cables did prevent T cs from degrading after electromagnetic loading cycles owing to the shortened twist pitch of the conductors, but a slight increase of T cs was observed. Visual inspections revealed no significant bent or buckled strands, but small deformations cannot be investigated visually. Thus, internal strain was measured by neutron diffraction and the internal strain states of the prototype CS conductors having long twist pitches and the improved short-twist-pitch (STP) CS conductors were evaluated. The results indicated that, after electromagnetic loading cycles, bending of the strands in the STP CS conductor was limited and compressive strain was reduced. Therefore, we determined that this STP is not only effective to prevent degradation caused by bent strands but it also increases T cs by reducing compressive strain.

Угол отхождения ветвей как показатель технологичности сорта яблони

Abstract. The article presents the results of study of apple varieties and hybrid progeny based on the branch union sign from the central conductor in order to identify genotypes for intensive gardening. The processability of the variety mainly depends on the genetically embedded structure of the crown of a particular genotype, which, among other things, is determined by the branch union. The study was conducted at the I.V. Michurin Federal Scientific Center, Central Black Earth Region (Tambov Region, Michurinsk). The objects of the study were Orlovim, Vympel, Rouville, Berkutovskoye, Fuji, Bylina, Honey crisp, Blagovest, Ligol, Academic Kazakov varieties. Ligol variety, widely used in intensive plantings, was selected as a control. Since the most important element of apple cultivation using intensive technologies is the formation of the crown of young trees, including pruning of fruit-bearing plants in the garden, these studies are relevant. The optimal branch union is considered to be an angle of 40-60°. It ensures reliable bonding of the central conductor and the outgoing branches. This breeding feature has been studied in the progeny of various combinations of crossing with the involvement of promising domestic and foreign varieties. As a result of the assessment of the hybrid progeny a wide range of variation of the branch union sign was revealed not only between different combinations of crossing, but also within a single family. The largest number of plants (more than 80 %) with an optimal branch union were observed in the following crossing combinations: Bylina x Honey crisp, Vympel x Academic Kazakov, Bylina x Vympel. In the future breeding for this trait, the most promising varieties are Akademic Kazakov, Honey crisp, Fuji, Vympel, Bylina. Keywords: apple tree, variety, breeding, hybrid offspring, branch union, intensive gardening, processability

Wideband Air‐Filled Coaxial Filter Line

ABSTRACTA design for manufacturing (DFM) of a well‐performing wideband coaxial filter line using direct metal laser sintering (DMLS) additive manufacturing is proposed. The demonstrated transmission line is an air‐filled coaxial line chosen for low loss and consistent group delay over the bandwidth. Transmission line theory is used first to account for the impact of the shorted stub needed to support the central conductor. Deviations due to parasitics are described to transition the design from an ideal model to a physical prototype. The constraints inherent in DMLS are discussed and accounted for throughout the DFM. This process is demonstrated with a prototype having return and insertion losses of greater than 10 dB and less than 1.64 dB, respectively, over a 5.3:1 bandwidth from 6.4 to 33.9 GHz with a flat group delay of 129 ps ± 7%.

Controllable coupling between fundamental modes in an asymmetric superconducting coplanar waveguide resonator

Controllable coupling between the odd and even fundamental modes of an asymmetric half-wavelength superconducting coplanar waveguide resonator is demonstrated. The resonant frequency of the even mode Ωe could be tuned by an external magnetic field, while the resonant frequency of the odd mode Ωo is field independent. To realize the tunability of Ωe, the central conductor of the NbN-based resonator was galvanically coupled to an array of Al-based rf-SQUIDs (radio frequency superconducting quantum interferometer device). These rf-SQUIDs are placed in only one resonator gap, ensuring its strong asymmetry. By adjusting the appropriate external magnetic flux Φ, equal frequencies of both modes were obtained. At this resonant point Ωo(Φ)=Ωe(Φ) an avoided level crossing of the eigenfrequencies was observed, demonstrating the coupling between the odd and even fundamental modes.

Design of X-Band Circulator and Isolator for High-Peak-Power Applications.

This paper presents a design of a X-band circulator-isolator for handling high-peak-power applications. The device consists of two cascade-connected ferrite circulators, with one dedicated to transmission and the other to small-signal reception coupled with high-power signal isolation. To improve the power capacity, a layer of poly-tetra fluoroethylene (PTFE) film is placed above and below the circulator's and the isolator's center conductors. Measurement results show that the device is capable of withstanding a peak power of 7000 W, with an insertion loss of <0.3 dB at the transmitting port. Similarly, it sustains a peak power of 6000 W with an insertion loss of <0.5 dB at the reception port. Moreover, the proposed design achieved isolation between the transmitting and receiving ends of >20 dB with a VSWR < 1.2 at each port. Thermal analysis shows that the maximum relative ambient temperature rise is 15.11 ∘C. These findings show that the proposed device achieves low-loss transmission of high-peak-power signals in the transmit channel and reverse isolation of high-peak-power signals in the receive channel.

Impact of Pressure and Temperature on Charge Accumulation Characteristics of Insulators in Direct-Current Gas-Insulated Switchgear

Direct-current gas-insulated switchgear (DC GIS) is an important device for promoting the lightweight and compact design of offshore wind power platforms. Gas pressure and temperature gradients are crucial factors that must be considered during the design process of the DC GIS. In this study, the multi-physics coupling model of basin insulators considering surface charge accumulation was established, and the corresponding real-sized insulator surface charge measurement platform was constructed. The effects of gas pressure and temperature gradient on the surface charge accumulation characteristics were investigated, respectively. The results show that the effect of gas pressure on the surface charge distribution characteristics depends on the dominant mode of surface charge. When volume conduction is dominant, the effect of gas pressure on the surface charge is negligible. However, when gas conduction is dominant, the accumulation of a uniform charge pattern on the insulator surface increases with the rise in gas pressure. Furthermore, due to gas convection, the temperature of the upper part of the DC GIS is significantly higher than that of the lower part, which leads to a temperature difference between the upper and lower surfaces of the insulator. The charge density on the insulator upper surface near the central conductor rises with the increase in load current.

Common‐mode current reduction in EMP coupling with the star‐quad cable having a reference conductor

AbstractThe coupling of electromagnetic pulse (EMP) with the star‐quad cable having reference conductor is analyzed by using the proposed model, which is based upon multi‐conductor transmission line theory. Expressions for common‐mode (CM) and differential‐mode (DM) currents are developed. Two cases are mainly discussed: the first case is the star‐quad cable with a central reference conductor, and the second case with the outside reference conductor. A rigorous comparison between these two cases shows that when the reference conductor is placed at the center, the magnitude of CM current is reduced dramatically, which is beneficial for electromagnetic compatibility (EMC). The CM current magnitude of the outside reference conductor is relatively very high due to the large CM current loop area, which is the least possible for the central reference conductor. There is no significant change in the DM current magnitude for both cases because the DM current has no direct dependence on the CM current loop area. A commercial software, FEKO, which utilizes the method of momentum (MoM), is used to compare the results of our proposed method, which are in good agreement.

Another look at the current-carrying wire in special relativity

In this paper we examine two models for a current-carrying wire in special relativity. The first model assumes an infinitely long wire and does not specify the source or return path for the current. This model is simple and easy to analyze, so it is often used in introductory textbooks to show the significance of special relativity for electromagnetism. The second model is a coaxial line with a battery at one end and a short circuit at the other. The center conductor of the line represents the wire of interest, and the outer conductor forms the return path for the current. The analysis for this model is more involved than that of the first model, but it provides information not available from that model. This new information answers questions a student might have when first encountering the simpler model.

Coplanar waveguide ground potential imbalance as a source of useful signal in near-field scanning microwave microscopy

Various techniques are available in order to obtain information on samples of a different nature in near-field scanning microwave microscopy (NSMM), with transmission-line resonator (TLR) techniques considered the most advanced in terms of sensitivity and resolution. In this paper, we focus on the development of TLR-based NSMM supplied by a new source of useful signal: coplanar waveguide ground potential imbalance. Electromagnetic modeling of the device and experimental scanning of two planar structures are conducted to examine the performance of the proposed technique. Both modeling and experimental results demonstrate the ability to distinguish symmetric inhomogeneity positions with respect to the central conductor of the coplanar waveguide by the phase of the imbalance signal. The thin-film structure scanning procedure displays the possibility of the proposed approach to resolve low-contrast structures with an accuracy of up to 98.7%.

Time Domain Simulated Characterization of the Coplanar Waveguide in an On-Chip System for Millimeter Waveform Metrology

We investigate the time domain characterization of a coplanar waveguide (CPW) based on an on-chip electro-optic sampling (EOS) system for millimeter waveform metrology. The CPW is fabricated on a thin layer of low-temperature gallium arsenide (LT-GaAs), and the substrate material is GaAs. A femtosecond laser generates and detects ultrashort pulses on the CPW. The forward propagating pulses are simulated using a simplified current source for the femtosecond laser at different positions on the CPW for the first time. Then, the influences of the CPW geometry parameters on the measured pulses are discussed. The varying slot width has larger influences on the amplitude of millimeter wave pulses than the center conductor width and the pumping gap. Finally, in the frequency range of 10 GHz to 500 GHz, the transfer functions calculated by the time domain pulses are in good agreement with the transfer functions calculated by the frequency domain ports. The above results are important for improving the measurement precision of the millimeter waveform on the CPW for millimeter waveform metrology.

The Growth Activity and Productivity of Apple Trees Depending on the Form of the Crown and the Time of Pruning

Abstract The apple tree is the most common fruit crop in the temperate climate zone. Modern intensive fruit cultivation involves the use of new, highly productive cultivars and cultivation technologies, thanks to the creation of small crown shapes with an increased number of trees per hectare. Reducing planting patterns and creating more dense plantation systems can significantly improve their yields. However, the limiting factor that can reduce tree productivity and deteriorate fruit quality is the degree of crown illumination. Ensuring even access of sunlight to all parts of the crown is the main task in the formation and pruning trees. The study aimed to determine the effect of crown pruning at BBCH 0 (winter) and BBCH 74 (early summer) and various types of crown formation on the growth activity and productivity of ‘Fuji’ and ‘Honeycrisp’ apple trees. A significant decrease (20%) in the number of newly formed shoots in the form of the French axis crown compared to the ballerina and slender spindle crowns was found. However, their length and total growth were significantly higher. The formation of the ballerina crown (with the removal of overgrown wood in the 25 cm zone on the central conductor above the lower tier of semi-cross-branched branches) contributed to a decrease in shoot length and total growth. The introduction of crown pruning in the summer also improved crown illumination – shoot length decreased by 17% and total growth by 12%. Specific productivity per bole cross-section and total shoot length was the highest in ballerina crown trees, followed by trees with a slender spindle crown, and trees pruned in winter and summer.

АГРОТЕХНИЧЕСКИЕ ПРИЁМЫ ДЛЯ ПОЛУЧЕНИЯ КАЧЕСТВЕННЫХ ОДНОЛЕТНИХ САЖЕНЦЕВ ЯБЛОНИ

The article presents an analysis of the collection and structuring of information on the methods of crowning annual seedlings of fruit crops in the nursery. The most effective and affordable agricultural practices for obtaining high-quality branched seedlings of fruit crops, as well as the effectiveness of their combinations, are analyzed. To improve the technology for the production of crowned annual seedlings, it is necessary to take into account the biological tendency of varieties to branch, the quality of cuttings of rootstocks in the first field of the nursery, apply mechanical methods of influencing the central conductor in combination with treatments of the seedling growth tip with plant growth regulators based on 6-benzylaminopurine or 6-benzyladenine and gibberellic acids.

Research and development of copper joint for ITER In-Vessel Coils

The ITER In-Vessel Coils (IVCs) are crucial components of the Tokamak fusion reactor. They are located within the vacuum vessel (VV) behind the blanket shield modules and are responsible for compensating for fast perturbations of the plasma. There are a total of 176 joints used to connect the IVCs, feeders and feedthrough. The joint structure consists of a central copper conductor, a mineral (MgO) insulation layer, and an outer stainless-steel jacket. Given the inaccessibility of the IVCs once the blanket modules are installed, the highest level of quality is required for the joints. One key item is the welding of the copper conductor which has to be done inside the VV. To address the high thermal conductivity of copper conductor and the challenging constraints working inside the VV, a preheating method by the arc of the welding head has been developed. Macro- and micro-structure examination were performed on the welding cross sections, and tensile tests were carried out to check the strength of the copper joint, which demonstrated that arc preheating does not have a significant impact on the heat-affected zone. After more than 40 welding attempts and several design updates, the copper joint has been successfully developed and can be repeatedly and successfully welded.

Семеношение кедра корейского (Pinus koraiensis Sieb. et Zucc.) при его интродукции в условиях лесостепи Воронежской области

The paper presents the research materials of Korean cedar introduction in the forest-steppe conditions of Voronezh region. Full compliance of its vital processes with the conditions of introduction is determined. The influence of the factor of tree placement in the territory — free or as part of other conifers on seed production — has been established. The increase of trees yield was revealed when artificial pollination was applied to them in comparison with non-pollinated trees. Attention was drawn to the moment of formation of multi-top tree crowns by formation of «empty» cone at the top of the central conductor. The high perspectivity of the breed cultivation in these conditions with obtaining both silvicultural and economic effect is pointed out. The forecast of yield of Korean pine crops under certain conditions of technology is given. Taking them into account in the creation of Korean pine seed object from 1 hectare of cultivated area it is possible to obtain the yield from the moment of grafting age in 25 years in the amount of 123 kg of nuts.

Permittivity measurement of biological tissues using interdigital capacitor based resonator

A CPW resonator etched on the central conductor is presented to measure the complex permittivity of biological tissues. In the unloaded condition, the proposed structure works as a resonator with a resonant frequency of 5.625 GHz. The proposed sensor is able to cover a wide range of permittivity measurement from approximately 5 (fat tissue) to 70 (malignant tissue) with sensitivity of 4.01 % and FDR( Frequency Detection Resolution) of 270 MHz . Breast phantoms with high fidelity need to be fabricated to imitate the various layers of the breast like skin, fat, glandular tissue, and tumor tissue regarding permittivity with different chemicals in different proportions. The major challenge in fabricating such phantoms is in creating an appropriate combination of substances to get the required characteristics for these biological tissues. A sample of various tissue types was fabricated using Gelatin and safflower-based recipes. The complex permittivity tissue phantoms are measured using a fabricated resonator. The measured dielectric characteristics of biological tissues are in good agreement with the theoretical values from the database.

Satisfaction-Based Multiobjective Optimization of the Design of a 65 GHz Millimeter-Wave Connector

It is difficult to simultaneously ensure the radio frequency (RF) performance and mechanical strength of 65 GHz millimeter-wave connectors. To address this, satisfaction-based multiobjective method for connector design optimization is proposed. An optimization model is developed for the structural dimensions of 65 GHz millimeter-wave connectors to minimize the voltage standing wave ratio, insertion loss, and deflection and maximum stress of the center conductor. The proposed optimization model concurrently satisfies the design requirements in terms of characteristic impedance, transmission frequency, and dielectric withstanding voltage. The model is optimized by innovatively using the multiobjective chaotic optimization algorithm in microwave finite-element simulations. The resulting optimal structure satisfies all performance requirements, thereby proving the rationality and feasibility of the proposed method. Moreover, this study establishes a novel design for other microwave devices to solve the problem of multiple performance index restrictions.

Tuning the thermoelectric properties of doped silicene nanoribbon heterostructures

In this work, we investigate the thermoelectrical properties of a silicene nanoribbon heterostructure composed of a central conductor fully doped with ad-atoms and connected to two pristine leads of the same material. Using a tight-binding Hamiltonian, we have calculated the system’s thermoelectric properties as a function of the geometrical confinement and external field. Our results exhibit an enhancement of the thermopower when a transverse electric field is applied to the conductor region for different temperatures. In addition, a violation of the Wiedemann–Franz law is observed around the ad-atom energy. Our results suggest the thermoelectric properties of doped silicene nanoribbons can be efficiently tuned with external perturbations.

Special Considerations of the Developmentof the Contact System of the Microwave Switch with the Frequency Range up to 18 GHz

The paper describes the development results and the construction of the high frequency contact system of the electromechanical microwave switch with the frequency range up to 18 GHz. The S-parameter measurement suggests that the achieved results are in line with the best in class competitive devices. The construction features the radially cut support beads, which enable simple and low-cost coaxial connector design that takes advantage of the monolithic center conductor design. The effects of the size of the radial cut on the effective dielectric parameters are researched using the quarter wavelength resonator method. The presented results of the research allow the accounting of the cut size on the microwave parameters of the switch. The presented construction of the developed resonator allows the coaxial support bead dielectric parameters control, implemented in the manufacturing process of the switch.

Miniature glass-metal coaxial waveguide reactors for microwave-assisted liquid heating

&lt;abstract&gt; &lt;p&gt;Microwave (MW) irradiation is recognized as an effective tool in industries related to pharmaceuticals, chemistry, nanoparticle synthesis, food, etc. In the hardware field, some research efforts are concentrated on creating miniature reactors using low-cost technologies aimed at on-demand chemistry or parallel synthesis of many drugs.&lt;/p&gt; &lt;p&gt;This paper reports on the development and characterization of novel miniature chemical-resistant glass-metal coaxial reactors based on a modified Liebig condenser. It is composed of two concentric glass tubes, one for the central conductor carrying MW current, and the other for the copper-foiled cylinder surrounding the first pipe. The gap between them is filled with a liquid that is pumped and evacuated by using shielded thin inlet/outlet glass tubes, which are melted and opened into this cylindrical cavity. The reactor's geometry allows for the direct soldering of miniature MW SMA coaxial connectors of 50-Ω impedance.&lt;/p&gt; &lt;p&gt;The developed components are studied analytically, numerically and experimentally. The frequency properties of reactors are measured with a network analyzer. The temperature trends are explored by using a variable high-power MW generator, power meters and temperature sensors.&lt;/p&gt; &lt;p&gt;These reactors demonstrate their relative insensitivity toward variations in the permittivity of filling liquids in the range of $3.75 &amp;lt; \varepsilon &amp;lt; 30$, as shown in simulations and measurements. They demonstrate the increase by two orders in the longitudinal modal penetration depth and a more homogeneous heating along reactors as compared to their hollow coaxial prototypes.&lt;/p&gt; &lt;p&gt;These glass-metal miniature reactors can be used in on-demand continuous-flow accelerated liquid heating, chemistry and pharmacy.&lt;/p&gt; &lt;/abstract&gt;

Неуловимый Гермес: к вопросу об идентификации Гермеса и Тота и мистериальном характере герметизма

The article treats the history of the identification of the Greek Hermes and the Egyptian Thoth, which eventually brought to existence the figure of Hermes Trismegistus, the founder of Hermeticism. The treatment of the complex genesis of this figure is connected with the solution of an important question for understanding the phenomenon of Hermeticism: what significance did Hermeticism grant to the mystery component? The problem stems from the structure of the Hermetic Corpus itself, which consists of philosophical texts of Greek origin and esoteric texts dating back to the Egyptian tradition. The history of Hermeticism is traced in the article as the history of the mutual influence of Ancient Egypt and Ancient Greece. Through the figure of Pythagoras I establish a connection between Pythagoreanism, Hermes and Egyptian mysteries. Plato, then, gives an original view of Hermes and Thoth; the next step is a transition to the Hellenistic Egypt, where the two deities were identified. The final step is the first evidence of Hermes Trismegistus and its origin. The article examines the reasons and possibilities for such an identification: the main functions of Hermes and Thoth, which at first glance are identical, present some discrepancies. First, the function of psychopompos: I draw attention to the concept of memory, power upon which is unique to the Greek Hermes; second, the power upon word, logos: while Hermes has the realm of the spoken word, Thoth is associated with the written text and thus magic (magical Egyptian practices are based on the power of the written word). The metamorphosis of Hermes from god to daimon and, finally, to man is also important (on the basis of the evidence of Plato and later hermetic mythology): this provided Hermes with the opportunity to become a central figure and conductor of mystical teachings, like Orpheus.