High Temperature Superconducting Conductor Research Articles

A newly developed 10 kA-level HTS conductor: innovative tenon-mortise-based modularized conductor (TMMC) based on China ancient architecture

We proposed a new type of high-temperature superconducting (HTS) conductor concept: modularized conductors (MCs) connected by Chinese traditional tenon-mortise (TM) connection structure, referred as TMMC (tenon-mortise modularized conductor). The conductor consisted of multiple concentric round sub-conductors with slots for stacking rare-earth-barium-copper-oxide (REBCO) tapes. Innovatively, the REBCO stacks in the adjacent sub-conductors were arranged with the fully-misaligned configuration to enhance the critical current’s isotropy with respect to magnetic field and reduce ac loss. For example, the angle between the adjacent stacks in the two adjacent sub-conductors was 45° if each sub-conductor contains 4 REBCO stacks. In order to construct the fully-misaligned configuration, the sub-conductors were designed with two open half-circular formers and connected by TM structure which makes the conductor modularized and simply to assembly and disassembly. Based on the design concept, a prototype conductor containing 160 REBCO tapes distributed in the four concentric sub-conductors was fabricated. The conductor’s measured critical current was 13.69 kA at 77 K and self-field, which was consistent to the simulation result. In order to further improve the TMMC’s engineering critical current density (J ce) and bending performance, we proposed two enhancement approaches: reducing the former’s thickness and re-arrange stacks in the outer sub-conductors. With the enhancements, both TMMC’s radius and J ce were comparable to the existing slotted-core conductor. The study shows the TMMC’s advantages of non-twisted structures, easy assembly, high-current carrying and low ac losses, which made it promising for constructing large-scale scientific devices.

Self-protected high-temperature superconducting demonstrator magnet for particle detectors

A high temperature superconducting (HTS) demonstration coil has been developed in the frame of the Experimental Physics department Research and Development program at CERN The magnet extends the recent experimental demonstration of aluminium-stabilised HTS conductors and supports the development of future large scale detector magnets. The HTS magnet has five turns and an open bore diameter of 230 mm. Up to 30 K, the coil was measured to be fully superconducting across four central turns at 4.4 kA, the maximum available current of existing power supply. The central magnetic field is 0.113 T, the peak field on the conductor is 1.2 T and the coil has a stored magnetic energy of 0.1 kJ. A 3D-printed aluminium alloy (Al10SiMg) cylinder acts both as a stabiliser and a mechanical support for the superconductor. The resistivity of Al10SiMg was measured at cryogenic temperatures, and has a residual resistivity ratio of approximately 2.5. The ability to solder ReBCO tapes (a stack of four REBCO tapes, 4 mm wide, Fujikura) to Al10SiMg stabiliser, electroplated with copper and tin, forming a coil, is demonstrated using tin-lead solder at 188 ∘C. The HTS magnet was proven to be stable when superconductivity was broken locally using a thin-film heater. Despite voids in the solder joint between HTS and stabiliser, no degradation of the magnet’s performance was observed after 12 thermal cycles and locally quenching the magnet. A numerical model of the transient behaviour of solenoid with partially shorted turns is developed and validated against measurements. Our work experimentally and numerically validates that using an aluminium alloy as a stabiliser for HTS tapes can result in a stable, lightweight and transparent magnet.

HTS conductor coil by in-situ winding technology for large-scale high-field magnet

High temperature superconducting (HTS) conductors have become important candidates to be used in large-scale high-field magnets, owing to its high critical current density as well as good mechanical properties. At present, there are various forms of HTS conductors proposed. In this work, we reported the fabrication of the REBCO HTS coil using in-situ winding technology. The six-layer coil with a diameter of 410 mm achieved a total current of 2562 A, and generated a central magnetic field of 7.8 mT at 77 K. The stress, deformation, and defect caused during conventional winding procedure could be significantly decreased using in-situ winding technology, indicating it has great potential for the large-scale high-field magnets in next-generation fusion reactors.

Preliminary Design Study on Non-Twisted HTS Conductor for Fusion Applications

Full transposition of superconducting wires within a conductor may not be a requirement for high temperature superconductor (HTS) magnet for fusion applications. Already, conduction-cooled 20 T model coil built with non-transposed HTS stacks has been demonstrated by Commonwealth Fusion Systems (CFS). Here, we discuss 3 possible stacked HTS cryogen-cooled conductor concepts for toroidal field (TF) magnet applications. The first one is somewhat like LTS conductors, the second, HTS stacks are capped by copper stabilizer, the last one, only stacks without copper. We simulate a simplified TF magnet model, 12 T, size of KSTAR, using the 3 conceptual HTS conductor designs. A comparative thermo-hydraulic analysis for a fast charging case has been carried out and its implications on HTS conductor design are further discussed.

Thermal Design of the Conduction-Cooled High Temperature Superconducting Magnet for Pulsating Magnetic Field

A conduction-cooled high temperature super-conducting (HTS) solenoid is fabricated to produce pulsat-ing 4 T magnetic field for magnetic refrigeration. HTS con-ductor of 245 m is wound as a solenoid with 112 layers each of which consists of 12 turns of the conductor. For a stable ramping operation of the magnet, AC loss inside the wind-ing pack should be effectively rejected to the heat sink. The thermal drains are inserted between the layers and con-nected to the magnet flange which is cooled by a commercial two-stage Gifford-McMahon cooler. They are made of Ox-ygen-Free High Conductivity (OFHC) copper, and has a width of 6 mm and a thickness of 50 μm. Thermal analysis is conducted to confirm the effect of the thermal drain on the AC loss heat rejection. AC loss of the magnet is esti-mated by using T-A formulation (current vector potential T and magnetic vector potential A). The ramp rate of the mag-net and the heat sink temperature are set to 0.1 T/s and 4.5 K, respectively. In the thermal diffusion calculation, each winding layer is considered as the lumped capacitance. In addition, thermal conduction between the adjacent lay-ers and that through the thermal drains are considered. The thermal analysis confirms that the conductor temperature of the winding is maintained lower than the operating limit of 20 K. Based on the results of the thermal analysis, the stable pulsating operation of the conduction-cooled super-conducting magnet is predicted to be feasible and is also confirmed by the experiment.

Analytical Modeling of Magnetization Losses in Twisted Stacked HTS Conductors

The European post-ITER fusion demonstrator reactor (DEMO) design activities have been ongoing for several years in the framework of the EUROfusion Consortium. The designs proposed for the DEMOnstration Fusion Power Plants (DEMO) magnets include options based on high-temperature superconducting (HTS) technology, namely as an Insert in the Central Solenoid (CS). This work describes the development of tools for the calculation of magnetisation losses in a twisted-stacked HTS cable, which represents one of the most promising configurations of HTS fusion Cable-in-Conduit conductors (CICC). This geometry cannot be tackled with the straightforward application of 1D or 2D models, given their inability to describe the twisting of the tape stacks. However, the methodology proposed in this work allows one to treat the twisting of the conductors by discretizing them in a set of straight pieces. A set of analytical equations is developed to compute the instantaneous power losses in the slab approximation. This fast, easy-to-use, open-access tool, can be employed for the computation of AC losses in the central solenoid modules of a tokamak. In particular, we have applied the model to study the HTS insert of the DEMO central solenoid.

Characteristics and causes of voltage observed at the current feeder of high-temperature superconducting WISE conductor

The HTS (high-temperature superconducting) conductor is a feasible candidate for constructing magnets for next-generation fusion devices because of its higher critical current in a high magnetic field. A new concept of the HTS-WISE (Wound and Impregnated Stacked Elastic tapes) conductor has been studied aiming to apply the fusion reactor magnet. Here, the WISE-U conductor is composed of stacked thirty REBCO tapes (10 mm width, 65 μm thickness, I c = 370 A @77 K, s.f.) wrapped by a stainless-steel coil tube which is inserted into the metal pipe. The 4 m-long REBCO tapes are folded with a radius of curvature of 35 mm in a hairpin-like structure. A low-melting-point metal U-Alloy 60 whose melting point is 60°C is poured into the pipe for impregnation to make the non-insulation conductor. The REBCO tapes and the current feeder made of oxygen-free copper were also impregnated with the U-Alloy 60 to connect. This fabrication method has the advantage of being easier to fabricate than the technique of connecting each tape using indium foil. The energization test results showed that a maximum current value of 16.9 kA was recorded at B = 5 T and T = 30 K, however, a burnout occurred in the current feeder before the critical current was determined. Then, the improved WISE conductor has been designed and tested which showed a maximum of 19kA was reached in the self-field and 20K. However, burnout still occurred in the current feeder section. In those experiments, the superconducting section has not been damaged at all. If this burnout had been avoided, a higher current-carrying capacity could have been obtained. Identifying the cause of burnout and improving the current feeder is required.

Performance of low-loss demountable joints between CORC® cable-in-conduit-conductors at magnetic fields up to 8 T developed for fusion magnets

High-temperature superconductors (HTS) are promising candidates for use in the high-field magnets needed in particle accelerators and fusion reactors. HTS conductor on round core (CORC®) cables and wires wound from ReBa2Cu3O7-x (REBCO) coated tapes are being developed for use in high-field magnet applications including fusion magnets operating at currents beyond 80 kA, requiring them to be bundled into cable-in-conduit conductor (CICC) configurations. The use of HTS cables enable demountable superconducting fusion magnets that would allow easier access to the fusion machine for maintenance and parts replacement. Such demountable magnets require practical, low-resistance joints, capable of injecting current uniformly into the many REBCO tapes that make up different cable designs. Optimization steps on CORC® cables have resulted in high-current terminations and joints with a joint resistance measured between a pair of 30-tape CORC® cables of 51 nΩ at 76 K and 1.9 nΩ at 4 K. Demountable joints between CICCs consisting of six CORC® cables arranged in flat and round configurations were also tested and compared to joints between low-temperature superconducting (LTS) CICCs consisting of NbTi Rutherford cables. Samples were paired into two configurations (LTS-to-LTS and HTS-to-HTS) with a demountable joint between them that were each tested in series with currents up to 10 000 A in an applied background magnetic field of up to 8 T. The total loop resistance of the HTS-to-HTS sample, including their terminations and joint, was about 4 nΩ at 4 K in self-field with the resistance of the copper pressed joint being less than 1 nΩ. At 8 T, the total loop resistance increased to 6.9 nΩ with the pressed joint contributing 1.4 nΩ. These initial tests prove the feasibility of producing remountable (dry) joints with low resistance between superconducting magnet windings in future compact fusion machines.

Mechanical properties evaluation of ReBCO CICC jacket based on super-austenitic stainless steel for CFETR high-field magnet

To excite stronger magnetic fields, high temperature superconducting (HTS) insert coils are planned for the next generation central solenoid magnet for China fusion engineering test reactor (CFETR). The development of high strength and high toughness jacket has become one of the challenges in the application of high-field cable-in-conduit conductors （CICC）. 0.2% proof stress of jacket should be over 1500 MPa at 4.2 K for HTS conductors, thus 316LN and JK2LB jackets developed by ITER do not meet the requirements. Nitronic 50 (N50) super-austenitic stainless steel material has great optimization potential for the development of jacket. Based on the modified N50 material, China prepared the CICC jacket and has done some R&D work on the N50 jacket. The entire process of ReBCO CICC preparation, including extrusion, bending and straightening, was simulated using the N50 stainless steel jacket. The N50 circle-in-square jackets prepared in China showed a yield strength greater than 1600 MPa and a fracture toughness KIC better than 110 MPa·m1/2 after cold work at 4.2 K. This paper will focus on the preparation, cold work processing and performance test of the N50 jacket. This study will present experimental data and discuss the feasibility of modified N50 as a high-magnetic field jacket material for next-generation fusion reactors.

Experimental study of stability, quench propagation and detection methods on 15 kA sub-scale HTS fusion conductors in SULTAN

High-temperature superconductors (HTSs) enable exclusive operating conditions for fusion magnets, boosting their performance up to 20 T generated magnetic fields in the temperature range from 4 K to 20 K. One of the main technological issues of HTS conductors is focused on their protection in the case of thermal runaway (quench). In spite of the extremely high thermal stability of HTS materials, quenching is still possible due to local defects along the conductor length or insufficient cooling. In such cases, the high stability results in the slow propagation of a resistive zone. Thereby, a risky hot-spot temperature (>200 K) can be reached if applying conventional quench detection methods at a voltage threshold of 0.1–0.5 V, typical for fusion magnets. Aiming at an experimental study of the phenomenon, a series of sub-scale 15 kA 3.6 m long conductors based on stacks of tapes soldered in copper profiles are manufactured at the Swiss Plasma Center, including twisted rare earth barium copper oxide (ReBCO) and bismuth strontium calcium copper oxide (BISCCO) triplets, non-twisted and solder-filled ReBCO triplets, as well as indirectly cooled non-twisted ReBCO single strands. Applying either an increasing helium inlet temperature, overcurrent operation or energy deposited by embedded cartridge heaters, critical values of the electric field and temperature are evaluated for a given operating current (up to 15 kA) and background magnetic field (up to 10.9 T). Once quenching is actually triggered, the quench propagation is studied using distributed voltage taps and temperature sensors able to monitor the external temperature of the jacket and the internal temperature of the conductor (helium or copper). Thanks to the recent upgrade of the Supraleiter Test Anlage (SULTAN) test facility, quench propagation in the conductors is measured up to a total voltage of 2 V and a peak temperature of 320 K. Furthermore, advanced quench detection methods based on superconducting insulated wires and fiber optics are also instrumented and studied. A summary of the test samples, their instrumentation and corresponding test results are presented in this work.

Comparative analysis on twisting characteristics of HTS quasi-isotropic strand and stacked-tape strand

With the gradual maturity of high temperature superconducting (HTS) technology, several HTS conductors with large critical current like quasi-isotropic strand (Q-IS) and twisted-stacked-tape cable (TSTC) were proposed, which can be assembled into cable-in-conduit conductor (CICC) and applied in power system and fusion magnets. The purpose of this paper is to study the twisting characteristics of Q-IS and stacked-tape strand (STS) with different stacking patterns under self-field at 77 K. The critical currents of two Q-IS samples and two STS samples are measured under increasing twist angle until they break. Each sample is composed of copper tapes and second generation (2G) REBa2Cu3Ox (REBCO, RE = rare earth) HTS tapes. For each type of conductor, one sample has a structure where REBCO tapes are stacked near the outside, while the REBCO tapes are stacked close to the inside in another sample. Simulation based on finite element method (FEM) and H-formulation is carried out for comparison. Numerical calculation of the normalized critical current versus the twist pitch is also conducted. Results show that each kind of strand with REBCO tapes stacked close to the inside have smaller critical twist pitches. Besides, self-field effect is dominant while the twist angle is small, but the effect of longitudinal strain gradually becomes the main factor as the twist angle increases. In general, the critical current degrading rates of STS samples are smaller than that of Q-IS samples. However, when the twist angle is relatively small, Q-IS samples show better critical current characteristics than STS samples.

Effect of winding methods: transport AC losses in CORC coils

AC losses undoubtedly increase the burden on the cooling system and affect the overall performance of high-temperature superconducting (HTS) cables. Therefore, AC losses in HTS cables are important design factors for large-scale HTS equipments. Extensive research has been conducted on straight, densely wound conductors. However, AC losses of bending/circular HTS cable conductors have not been sufficiently studied. In this article, the transport AC losses in a circular HTS conductor coil bended by a conductor on round core (CORC) type cable were investigated using experiments and numerical simulations. The effect of different winding methods was also studied. First, the modeling method of the three-dimensional simulation and the experimental procedures were presented. The simulation results of the straight densely wound conductor (SDWC) and circular densely wound coil (CDWC) were compared with the corresponding experimental results. Finally, the winding method for the CDWC was optimized using both the simulation and experimental approaches. Both the experiments and simulations showed that reducing the tape-to-tape frontal area was able to decrease the transport AC loss, and the results show that the optimum winding angle of the HTS CORC coil was 24.15°. Overall, the modeling and experiments provide useful optimization strategies for designing winding structures of high-performance CORC coils/magnets.

Critical current and n-value prediction of second-generation high temperature superconducting conductors considering the temperature-field dependence based on the back propagation neural network with encoder

The qualities of superconducting conductors are usually characterized by their critical current and n-value. In this paper, the critical current and the n-value of the second-generation (2G) high temperature superconducting (HTS) conductors considering the temperature-field dependence are predicted by a back propagation (BP) neural network as J c(B, θ, T) and n(B,θ,T). A correlation exists between the critical current and the n-value, thus in our BP neural network, the tasks of estimating the critical current and the n-value can be carried out in one network. The outputs used to predict the critical current and the n-value share the same hidden layers of the network, and therefore the critical current and the n-value can be calculated simultaneously. The critical current and the n-value of HTS conductors vary for different manufacturers and even for the same manufacturer but different production batches. In our BP network, we use an encoder structure to encode different manufacturers and production batches to ensure that the network can be adapted to the HTS conductors so produced. The predictions on three different samples of HTS conductors are carried out and the results are compared with those obtained from linear interpolation at different temperature-field conditions. In addition to the high accuracy, when compared with the linear interpolation, the proposed network can suppress the fluctuations existing in the experimental data and ensure the prediction results to be more reasonable. The time required for the proposed network to obtain the prediction results of the critical current and the n-value is also discussed, which is within 5 s. Therefore, the proposed network has the potential to be applied to the optimization and analysis of the superconducting related equipment.

Progress of HTS STARS Conductor Development for the Next-Generation Helical Fusion Experimental Device

A High-Temperature Superconducting (HTS) magnet is being considered to for use in the next-generation helical experimental devices. Three types of large-current HTS conductors are being developed, and one of them is the STARS (Stacked Tapes Assembled in Rigid Structure) conductor which uses HTS tapes with a simple stacking technique. Following the proof-of-principle experimental results obtained in the former 100-kA-class prototype hand-made conductor sample, an actually applicable conductor is being developed with a rated current of 18 kA at a temperature of 20 K and a magnetic field of ∼10 T. One of the crucial requirements for this conductor is to have a high current density of 80 A/mm2. In the first phase of the development, a 3-m short sample was fabricated by applying laser-beam welding to the stainless-steel jacket. It was tested in liquid nitrogen at 77 K with no external magnetic field. Then the sample was tested in gaseous helium at 20 - 40 K under a magnetic field of 6 - 8 T, and the results show that the basic requirements were satisfied.

Subscale HTS Fusion Conductor Fabrication and Testing in High Magnetic Background Field

In actual or future fusion machines like ITER, JT-60SA, W7-X or the present EU-DEMO design, low temperature superconductor (LTS) cables are used or planned to be used in the magnet system to create the strong magnetic field necessary for plasma confinement. High temperature superconductors (HTS) offer the potential to increase the magnetic field strength in fusion magnet systems even further, allowing to build more compact fusion machines or to realize higher flux swings in central solenoids. In this work, two HTS conductors were fabricated and characterized by high current testing at 77 K in self-field conditions and at 4.2 K with an external magnetic field up to 12 T. Both samples offer the same amount of superconducting HTS tapes but differ in the assembly process and termination type. These tests were intended to validate the current KIT design of a HTS CroCo triplet conductor and to qualify a low degradation cable manufacturing process.

Co-Wound Superconducting Wire for Quench Detection in Fusion Magnets

High temperature superconducting (HTS) materials are widely utilized in various design proposals for fusion magnets, resulting in enhanced performance of the machines compared to the past. However, a reliable quench detection in HTS conductors remains an open issue. Using a co-wound superconducting wire of high normal state resistance as an electrically insulated and thermally coupled sensor provides strongly increased sensitivity for the voltage-based quench detection methods. Furthermore, resistance of the wire can be practically proportional to the size of the normal zone, even though the location of the hot-spot cannot be identified. We present adaptation of this method for fusion conductors by considering various wire options, such as MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wires in a highly resistive matrix, non-stabilized Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wires and (K,Na)-Ba122 wires. The insulated wire of a small diameter (<1 mm) can be embedded in the steel jacket, thus barely affecting the conductor design and manufacturing aspects. Alternatively, if installed within the cable space, the wires might even allow monitoring of quench dynamics among the strands. Our first experimental demonstration is planned in a sub-scale ReBCO cable-in-conduit sample, which will be tested in the SULTAN test facility recently upgraded for DC operation in resistive samples with the transport currents up to 15 kA and maximum voltage of 10 V.

36-5-3] Stabilizer에 따른 2세대 고온 초전도 선재의 전기적 열화특성

2G High temperature superconducting(HTS) conductors are usually considered as appropriate superconductors for a superconducting coil to develop an applied superconducting apparatus such as a superconducting fault current limiter(SFCL), a superconducting cable, and a superconducting accelerator with high voltage or high ramping-up rate condition. The electrical degradation characteristics of HTS conductors due to electrical breakdown should be taken into consideration because high electric field intensity induced by high operating voltage or rapid ramping-up rate can affect the dielectric stability. In this study, the electrical degradation characteristics of 2G HTS conductors with different metal stabilizers made by SuNAM Co., Ltd. are analyzed and compared through dielectric experiments. As results, the most appropriate type of a 2G HTS conductor is recommended to manufacture superconducting apparatuses with a high voltage or rapid ramping-up rate condition.

Dynamic resistance and total loss in a three-tape REBCO stack carrying DC currents in perpendicular AC magnetic fields at 77 K

In many high-temperature superconducting (HTS) applications, HTS-coated conductors carry a DC current under an external AC magnetic field. In such operating conditions, dynamic resistance will occur when the traversing magnetic flux across the HTS conductors. Consequently, AC loss within the superconductors is composed of the dynamic loss component arising from dynamic resistance and the magnetization loss component due to the AC external magnetic field. This AC loss is one of the critical issues for HTS applications, such as persistent current switches, flux pumps, and rotating machines. In this work, the dynamic resistance and the total loss in a three-tape HTS coated conductor stack were measured at 77 K under perpendicular AC magnetic fields up to 80 mT and DC currents (I dc) up to the critical current (I c). The stack was assembled from three serial-connected 4 mm wide Superpower wires. The measured dynamic resistance results for the stack were well supported by the results from 2D H-formulation finite element modelling (FEM) and broadly agree with the analytical values for stacks. The FEM analysis shows asymmetric transport DC current profiles in the central region of the superconductor. We attribute the result to the superposition of DC currents and the induced subcritical currents which explains why the measured magnetization loss values increase with DC current levels at low magnetic field. The onset of dynamic loss for the stack for low i (I dc/I c) values is much slower when compared to that of the single tape and hence the contribution of the dynamic loss component to the total loss in the stack is much smaller than that of the single tape. Dynamic loss in the stack becomes comparable to the magnetization loss at i = 0.5 and becomes greater than the magnetization loss at i = 0.7. Both magnetization loss and dynamic loss in the stack are smaller than those of the single tape due to shielding effects. The difference between the Q total behaviours in the stack and single tape is due to the variation of the penetration depths of the stack and single tape at the different magnetic field amplitudes.

Temperature-field-angle dependent critical current estimation of commercial second generation high temperature superconducting conductor using double hidden layer Bayesian regularized neural network

We estimated the critical current of the second generation (2G) high-temperature superconducting (HTS) conductor using neural network fitting methods. The critical current of 2G HTS conductors depends on magnetic field strength and angle as well as on temperature, Ic(T, B, θ). Moreover, the critical current values vary for 2G HTS conductors from different manufacturers. In this study, we addressed three challenging issues in critical current assessment by neural network fitting methods, namely 90° asymmetry, a wide range of temperature-field-angle dependence, and different manufacturer conductor differences. Prediction models for three commercial HTS conductors were trained and evaluated by convergence, accuracy, and robustness. The linear regression correlation coefficient R was approximately equal to 1 for the three models. The critical current estimation obtained from the proposed method was compared with the critical current estimation from the interpolation method at different fixed temperatures using a multi-width no-insulation magnet. The model computation speed was also discussed. The proposed model needed only 2.7 s to compute 10 million data sets. Therefore, the convergence, accuracy, reliability, and speed of the proposed method prove that it can be used in a wide range of industrial applications and academic fields.

Fabrication and Critical Current Evaluation for HTS Twisted Cables Consisting of Soldered-Stacked-Square (3S) Wires

High temperature superconducting (HTS) conductors or cables can be considered as a significant candidate in various large-current HTS applications. To develop large-current HTS conductors or cables, HTS wires of small square dimension have been suggested and studied in our group, and the wire is named Soldered-Stacked-Square (3S) wires. Based on 3S (2+10c)-wires composed of two HTS tapes and ten copper tapes, a novel HTS twisted cable structure named “2mm-7-cable” including seven (2+10c)-wires was firstly proposed in this study. This structure is most similar to the cable in conduit conductor (CICC) structure of low temperature superconductor (LTS). To begin with, we introduced the fabrication process of the 2mm-7-cables, including preparation of soldered-stacked-square (3S) wire, winding copper wire process, twisting and cabling process. Then, their critical current performance was evaluated experimentally. The test results of critical current show that when the voltage-lead is directly connected to the surface of the (2+10c)-wire after removing the copper wires of both ends, the measured resistance of 2mm-7-cable will be greatly reduced. And the summation of the critical currents of seven (2+10c)-wires are almost identical to the one of the 2mm-7-cable. Thus, the feasibility of the fabrication method for the novel HTS twisted cable is partially verified in this study.