Cable-in-conduit Conductor Research Articles

Experimental study on the critical current in highly flexible REBCO cables under copper tube compaction

The Institute of Plasma Physics Chinese Academy of Sciences (ASIPP) is developing the high-current REBCO cable-in-conduit conductor (CICC) for use in the Central Solenoid (CS) coil of the next generation nuclear fusion device. The aim is to develop a CICC comprising six REBCO sub-cables to satisfy the requirements of operation with a current of around 46 kA and a peak field of up to 20 T. Sub-cables, as crucial components within CICCs, play a pivotal role in ensuring the mechanical support strength and current-carrying stability of the entire CS coil system. Therefore, a process was developed in this paper for the first time to make a sub-cable that meets the requirements by inserting the Highly Flexible REBCO Cable (HFRC) cable into a copper tube and compacting it. Meanwhile, the feasibility and reliability of this process were evaluated and optimized using experimental methods at 77 K and self-field. The result indicated that sub-cables without copper tape protection experienced a 25.42% degradation in critical current (IC). In contrast, when at least one protective layer of copper tape was used as a protective buffer between the HFRC cable and the inner wall of the copper tube, the IC remained stable within a 1% error margin after compaction. These findings demonstrate the feasibility of this sub-cable preparation process. Meanwhile, this compaction method provides a solid process foundation for the development of full-size conductors in future magnet applications.

The first CICC-type Bi-2212 insert coil for high-field applications up to 20 T

Abstract As the need for high-magnetic field magnets, this article made the first cable-in-conduit conductor (CICC) -type Bi-2212 insert coil. The Bi-2212 conductor consists of 24 wires, an Ag tube, and a 316 LN jacket. With the optimized heat-treatment regime, the insert coil exhibited excellent current-carrying capacity under magnetic fields up to 20 T: the Ic of the coil was up to 5.4 kA under 20 T backfield. With the ‘Pre-OP before cabling’ process, the void fraction was precisely controlled. Besides, the insert coil exhibits excellent stability with the electromagnetic loads and quenching process: no obvious change in performance was detected even when the electromagnetic loads increased to 101 kN m−1; after the quench event where the voltage on the insert coil was up to ∼4000 times criterion, no degradation was detected. The excellent performance of the Bi-2212 insert coil gives a solid foundation for the development of full-size Bi-2212 CICC for high-field applications.

Manufacture process and cabling optimization of Bi2212 CICC

The Bi2212 cable-in-conduit conductor (CICC) is a composite soft material and is sensitive to stress-strain and brittle breakage. The cabling tensions are critical parameters for the CICCs and have undergone trial production many times to achieve effective cable control. Unreasonable tension will cause circumferential and axial motion, resulting in deflection bending, rotation fluctuations, and wire slip. This study investigated the manufacturing process of the Bi2212 CICC, optimizing the cable twisting process and reducing manufacturing consumption and damage. Additionally, optimized tensions of the Bi2212 CICCs during the cabling process, focusing on pay-off tension, rotation speeds, and traction tensions were presented. Finally, the results are tested and verified in the factory to examine the wire jumpers, serpentine bending, and pitch fluctuations. This research provides useful references for future cable fabrication of the HTS CICCs.

Co-simulation of cool down process from 300 to 80 K for ITER Tokamak

Dynamic simulation of Tokamak superconducting magnet system has been conducted to investigate the cool-down process from 300 to 80 K. The simulation focuses on the cool-down speed variations with respect to the global temperature gradients in the different coils; Toroidal Field (TF) coil, TF STructure (TF-ST), Central Solenoid (CS) and Poloidal Field (PF)/Correction Coil (CC) systems. As imposing the maximum temperature gradients dT max ≤ 50K, the speed should be adjusted, ensuring the limited mechanical stresses due to thermal contractions. So far, the process simulation of Tokamak cryogenic system has been concentrated on the Deuterium Tritium (DT) operation phase; therefore, it is necessary to revise the model to extend its capability for the cool-down; for example, the thermo-hydraulic properties of Cable-in-Conduit Conductor (CICC) for each coil, mechanical properties of materials for the magnet system. The cool-down process is implemented at the helium refrigerator by utilizing LN2 heat exchanger up to 80 K. Its speed is set at -0.8 K/hr as a baseline, which can be controlled by the global temperature gradients in the magnet system. The process will be on hold as dT max ≥ 50K, and resumed once dT max < 50K. The paper discusses the cool-down processes of the Tokamak and identifies the impact on the speed, dT i/dt, of each component.

Conceptual design study of a large bore superconducting test facility magnet, SUCCEX

A 16 Tesla, large bore superconducting magnet for testing the superconducting Cable-in-Conduit Conductor (CICC) is being designed in parallel with the design of the steady state Korea fusion demonstration reactor (K-DEMO) magnet system. The test facility magnet, named SUperConducting Conductor Experiment (SUCCEX), was designed in 2014 and some design modifications of the magnet have been conducted since 2020. The peak magnetic field of the K-DEMO toroidal field coil is about 16 T, and thus the required background field of the conductor test magnet is expected to be over 15 T in a large bore of 600 mm diameter. The background field will be in addition to the K-DEMO conductor sample's self-field. To reach the target magnetic field, high current density Nb3Sn strands (Jc > 1100 A/mm2 at 4.2 K, 16 T) were employed in the design of the high field CICC. The modified SUCCEX magnet consists of concentric solenoids, with a high field inner coil (IC) and low field outer coil (OC). They are connected in series with each other, and the operating current is about 24 kA. In this study, the overall design concept is presented in relation to the results of electro-magnetic, structural analyses.

Mechanical and physical properties of modified N50 steel at cryogenic temperatures

China Fusion Engineering Test Reactor (CFETR) has more advanced design parameters compared to the International Thermonuclear Experimental Reactor (ITER), particularly demanding a high yield strength (over 1500 MPa at 4.2 K) for jacket material in the cable-in-conduit conductor (CICC). Modified N50 austenitic steel, due to its excellent mechanical properties at liquid helium temperature, has been identified as a promising candidate material for the jacket material. However, while some research focuses on the mechanical properties of modified N50 steel at cryogenic temperatures, little is known about the cryogenic physical properties that are critical for conduit jacket applications. In this study, a modified N50 steel was prepared and characterized in terms of tensile properties and physical properties at cryogenic temperatures. We tested the tensile properties of the modified N50 at 4.2 K, 77 K, and room temperature (RT). Additionally, we measured the thermal conductivity, thermal expansion, specific heat capacity, and magnetization of the modified N50 from 4 K to 300 K. These results could provide a more comprehensive reference for applying the modified N50 steel in jacket materials for the CFETR.

Metallographic investigation of first full-size high-Jc Nb3Sn cable-in-conduit conductor after cyclic loading tests

In order to verify the feasibility of applying high-Jc Nb3Sn strand in fusion magnet, a full-size cable-in-conduit conductor (CICC) with short twist pitch (STP) cable pattern was manufactured and tested in SULTAN facility at SPC, Switzerland. Three levels of cyclic electromagnetic (EM) load were applied on the sample stepwise, no visible decrease of current sharing temperature (Tcs) was observed until the EM load increased to 80 kA × 10.8 T, after that the Tcs decreased dramatically with the EM cycles, which suggested that irreversible deformation, causing a change in the strain state, or even damage has occurred in the superconducting strands. For investigating the reason which caused the conductor performance degradation, the tested conductor was dissected for metallographic observation. Eight segments which subjected to different EM loads were extracted from one of the legs, the geometric feature changes of the cable cross-sections were analyzed and compared. A good correlation was found between the decrease of the Tcs and deformation of the cable cross section. A mass of cracks were found on the sub-elements of strands in the segment which subjected to highest EM load, but the amount of crack is much lower in other segments. Combining the analyses, it is speculated that the critical EM load which causes irreversible degradation is between 850 kN/m and 870 kN/m for this conductor. The results could be a reference in high-Jc Nb3Sn CICC design.

Performance test of REBCO CICC sub-cables with 10 kA current under 20 T background field

While commercially manufactured rare earth barium copper oxide (REBCO) tapes show significant promise in facilitating the operation of fusion magnets with magnetic fields above 15 T, the design and development of highly stable cable in conduit conductor (CICC) technology is very important to achieve their practical application. To find a good solution for this demand, the Institute of Plasma Physics, Chinese Academy of Sciences, proposed two kinds of CICC design concepts, which are both manufactured from a sub-cable formed by winding REBCO tape around a stainless steel spiral tube. As part of the ongoing activities to develop an REBCO CICC, two sections of sub-cable specimens were manufactured and bent into a U-shape for testing under magnetic fields up to 20 T. A sub-cable specimen with 30 commercial 4 mm wide REBCO tapes displayed around 10 kA at 4.2 K and a background magnetic field of up to 20 T. It also showed stable operation under an electromagnetic (EM) load of around 200 kN m−1, which is above the 150 kN m−1 required by the designed CICC sub-cable. However, the calculated I c of the other specimen degraded from 8.8 kA to 8.5 kA when cycling with an EM load of around 160 kN m−1. The lower calculated n-value at 77 K and self-field as well as the observed imprints on the disassembled tape edges suggested that defects were generated in the cable during cabling, bending to the sample holder or operation with high EM and thermal loads. These results exhibit the potential and feasibility of using high flexible REBCO cable (HFRC) sub-cables for high-field fusion magnets. However, the winding parameters need to be optimized to ensure safe operation in more complex conditions, such as in tokamaks, especially if using tapes similar to those used in sample-B in this study. Moreover, it is imperative to establish much more rigorous requirements for coil manufacturing processes in order to avoid the occurrence of defects in the tapes.

Progress on the R&amp;D for the New Cable-in-Conduit Conductor Type of the MADMAX Dipole

The concept of Cable-in-Conduit Conductor (CICC) has been adopted for the large superconducting dipole of the MADMAX project. It is based on a multistage cable inserted in a potentially pre-hardened copper profile and then compacted together down to the final rectangular shape. NbTi technology and internal cooling with stagnant superfluid helium is kept in order to operate at 1.8 K. On the other hand, the use of copper instead of stainless steel as for common CICCs for fusion magnets led to an extensive R&D phase. The need to improve the mechanical properties of the conduit to withstand the high level of mechanical stress in the magnet requires significant level of cold working, which can be obtained by compacting a profile with a large initial cross-section. Manufacturing with high compaction over long lengths, within certain tolerances, represented a challenge to find the initial shape of the profile. To deal with it, different compaction scenarios were simulated by Finite Element Methods on two copper profiles eventually manufactured. A mechanical tests campaign aimed to investigate the properties of the processed samples was also carried out. In the present work, the main characteristics of the new MADMAX CICC will be summarized, the R&D phase will be presented and the results will be widely discussed.

Design Evolution of MADMAX Conductor to a Nb–Ti Cable in Copper Conduit

The MADMAX (MAgnetized Disc and Mirror AXion) project aims at detecting axion dark matter in the mass range around 100 μeV. Prerequisite for success is a very large dipole (1.35 m warm bore) with a high magnetic field up to 10 T. A first conductor design made of Nb-Ti Rutherford Cable On Conduit Conductor with a hole in the copper conduit (RCOCC type) was already presented. The coolant is static bath of superfluid helium at 1.8 K. Unfortunately, no conductor manufacturer with an available production line was found to take in charge the cable insertion/soldering process. Actually, such a production line should be compatible with large conductor section (∼400 mm²) including a solder wave device. The type of conductor was changed to use a line developed for ITER Cable In Conduit Conductor (CICC). Nevertheless, the jacket part was kept in copper. The main evolution of the MADMAX conductor design is presently reviewed. The final outer dimensions of the conductor, the void fraction and the required cold work of the copper induces a reverse engineering challenge on the initial shape of the copper profile. Then, the cable geometry modification involves a lots of differences in terms of self-field, strand diameters, transposition paths, joints technique and conductance between the strands and the stabilizer. The mechanical aspects are subject to evolution for the project due to the magnetic design optimization and conductor type change. A sub-modeling approach is used to detail the stress level in the stabilizer jacket. The possibility of wire motion and wire deformation during the conductor compaction in the production line is also discussed. Concerning the thermal analysis, the major difference is the thermo-hydraulic quench back that induces a much higher pressure drop of the helium in the conduit. So, higher pressure induced higher helium velocity and a fast detection after a quench event in superfluid environment becomes possible.

Development, Integration, and Test of the MACQU Demo Coil Toward MADMAX Quench Analysis

The MADMAX project aims at detecting axion dark matter in the mass range of 100 μeV. To facilitate axion to photon conversion with detectable rate a superconducting dipole magnet with a large bore is needed. The MADMAX dipole magnet has to generate ∼9 T in a 1.35 m aperture over ∼1.3 m in length. A key challenge for a magnet made of a cable in-conduit conductor (CICC), operating at 1.8 K with an indirect bath cooling is the quench detection. In order to validate feasibility, a mock-up coil with a quench behavior scalable to MADMAX was designed and produced. The paper gives an overview of the technical details of the MACQU test coil. The conductor, the magnet, the busbar and the supporting and cryogenic systems were designed at CEA. The cable was manufactured in China at the Chang Tong INC from WST Nb-Ti strands, the insertion and compaction was achieved in the ASIPP institute with a copper profile from Aurubis. The winding of the coil and the busbar pre-forming were performed at Bilfinger Noell as well as the assembly of the supporting structure and the thermal shield. The magnet was integrated in the JT60 test station at CEA Saclay and extensively tested. The magnet current reached 80% on the loadline instead of 90% as expected at nominal. The limitation is likely coming from uneven current distribution at the extremity of the magnet at the connection box location. Nevertheless, quench tests were successfully performed at constant currents from 10 kA to 17 kA. They proved that the initial quench velocities are of the order of 1 m/s to 10 m/s, high enough to safely detect a voltage drop in MADMAX and discharge the magnet. In addition, a thermo-hydraulic quench back effect was observed in the MACQU coil cooled by superfluid helium.

Conductor Qualification and Fabrication for the MACQU Solenoid

A solenoid mock-up called MACQU was designed and tested at CEA Saclay to study the quench propagation in a MADMAX like conductor, i.e. a cable-in-conduit conductor (CICC) with copper conduit cooled at 1.8 K with stagnant superfluid helium. Compared with classic CICCs for fusion magnets, the presence of a cable wrapped by a copper tape and inserted in a copper conduit represented new features from the manufacturing point of view that required a R&D program. In this paper the whole process that led to the final conductor designed for the solenoid MACQU, from strand characterization to the fabrication through the R&D and acceptance phases is described.

The research on the influence mechanism of internal deformation for the performance of Bi-2212

Cable-in-conduit conductor (CICC), one of the most promising conductors for manufacturing magnets in magnetic confinement fusion devices, has attracted lots of attention. In the production of CICC, porosity control is necessary for its stability. The porosity control is usually realized by the diameter-reducing process, which would also lead to indentation damages to the elements of CICC-superconducting wires. In this article, systematic research of indentation damages was carried out on the next generation of high-temperature superconducting materials–Bi-2212 wires. The results indicate that the current carrying capacity of the indentation-damaged wire would first keep steady and then show exponential decline with the increase of indentation depth. The wires subjected to pre-overpressure (pre-OP) treatment exhibit slightly improved resistance against indentation damage at shallow indentation depths. However, their critical current (I c) deteriorates more rapidly at greater indentation depths when compared to wires that have not undergone the per-OP process. The following structural characterization analyzed the reasons for the property changes with the help of scanning electron microscopy, energy dispersive x-ray spectroscopy, computed tomography, and hardness tester. Misalignment between the Bi-2212 grains and shaped filaments was found in the indentation-damaged wires, with which the degradation in I c of the wires and the differences in properties of the two kinds of wires were further discussed.

Conceptual Design Study of a Test Facility Magnet for Fusion Conductor Samples

Design studies of the steady-state Korean fusion demonstration reactor (K-DEMO) magnet system have been conducted since 2013. The maximum magnetic field of the K-DEMO toroidal field (TF) coil is expected to be over 16 T. A high field superconducting magnet and a facility for testing the K-DEMO TF conductor samples are also being designed to prepare for the development of the K-DEMO TF conductor. To test straight fusion conductor samples compatible with the K-DEMO TF conductor, it is essential to have a large, 150 mm wide by 120 mm high sample space in the magnet. The required maximum magnetic field of the fusion conductor test magnet is expected to be over 15 T. The field consists of about a 15 T background field and some self-field. Both high current density Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strands and high temperature superconductor (HTS) tapes are candidates for the superconducting materials for the magnet. In this work, two conceptual design study models of the high field magnet are introduced - a planar racetrack dipole based on HTS tape (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> > 200 A/4-mm at 4.2 K, 18 T) cable-in-conduit conductor (CICC), and a non-planar flared end saddle dipole based on Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> > 2600 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 4.2 K, 12 T) CICC. 2-dimensional magnetic and mechanical analyses of both magnet models were performed and the main features of the models are presented.

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.

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.

Stability Analysis of 14-T-Level High-Performance Nb3Sn Cable-in-Conduit Conductor for a Toroidal Field Coil

In view of the fact that the fusion power of fusion reactor is proportional to the fourth power of the toroidal magnetic field, the design of toroidal field (TF) magnetic system is particularly important for achieving higher operating parameters. In order to meet the confinement requirements of high plasma parameters, the high field region of the TF magnetic system can be wound by high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn cable-in-conduit conductor (CICC), with a maximum magnetic field reaching 14.32 T. Since the stable operation of the TF magnetic system relies heavily on the stability of the superconductor, a stability analysis of high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn CICC conductor has been performed. The results indicate that the current sharing temperature of the conductor is 6.9 K under extreme working conditions ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> = 14.32 T), which meets the design requirements; the minimum quench energy (MQE) is 116 mJ/cc under short perturbation, but under long perturbation it is only 20.3 mJ/cc. Therefore, several options may be available to increase the MQE of the conductor, such as reducing the strain, operating current and thermal resistance, or increasing the helium mass flow rate. In addition, the quench behavior of the CICC conductor is also evaluated. Studies have shown that increasing the area of copper and decreasing the thermal resistance and quench detection threshold voltage can lower the hot spot temperature. These analyses provide references for the design of 14-T-level high-performance Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn CICC conductor and its quench protection system.

Void fraction research and destructive examination of CFETR toroidal field coil protype joints

The CFETR toroidal field coil (TFC) is designed to generate a peak magnetic field of 14.5 T at 4.2 K, with an operating current of 95.6 kA. The creation of superconducting joints is one of the most delicate parts of TF winding package (WP) fabrication, as the superconducting joints play an important role in the electrical and cooling circuit connection. ASIPP has produced a prototype sample containing three types of joints using a CFETR TF cable in conduit conductor (CICC) in 2022 and has obtained good resistance test values. This paper describes the study of joint void fraction (VF) and pixel-based image recognition analysis, and evaluation of contacts between conductive components. And the solution of the expansion of the twin box terminal in the manufacturing process and the groove design examination of spliced joints.

Evaluation of the mechanical properties of CICC jacket for CFETR superconducting magnet

Modified 316LN and JK2LB stainless steel were selected as candidate jacket materials for superconducting cable in conduit conductors (CICC) of the China Fusion Engineering Test Reactor (CFETR). Different superconducting conductors need to undergo different cold working deformations and different heat treatment processes during the manufacturing process. Therefore, a systematic investigation was done to examine the influence of different cold working deformations and different heat treatment processes on the mechanical properties of the two materials. The mechanical properties of materials were measured at 4.2 K, 77 K and 300 K, and Young's modulus, yield strength (0.2% offset), ultimate tensile strength and elongation at failure were reported. In addition, the fracture morphology of all tensile samples was observed by backscattered-electron imaging (BSEI). The results show that the effect of increasing cold deformation of extrusion to improve the yield strength of the jacket is not obvious. In addition, the heat treatment schemes of different superconducting materials have limited influence on the performance of the jacket. These two materials have the potential to be used in CICC conductors prepared from different superconducting materials.

Performance of the Cable-in-Conduit Conductors for Super-X Test Facility

Following the conceptual design, the engineering design of the dc magnet and cable-in-conduit conductor (CICC) for the Super-X test facility has been done in 2021. Totally three types of conductors with different structures were designed for the three pairs of coils in the dc magnet, respectively. High- <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">J_c</i> Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand (J <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> ∼2200 A/mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at 12 T, 4.2 K) was applied to high field and middle field coils for reducing the radius of the dc magnet. In order to qualify if the designed parameters of the conductors could fulfill the performance criteria, three pairs of short samples have been manufactured and tested successfully in the SULTAN facility at SPC, Switzerland. Test results and analysis show that dc performance of the three types of conductors can meet the design criteria. The conductor qualification process including the sample preparation, test results, and analysis are presented in this article. The HFC and LFC conductors exhibit different ac loss behavior to the MFC conductor, which is discussed in the article.