Performance of highly flexible sub-cable for REBCO Cable-In-Conduit conductor at 5.8 T applied field

Self Cite

Although the commercially manufactured REBCO tapes exhibit a strong potential to enable future fusion magnets operation with a magnetic field above 15 T, 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, Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) proposed two kinds of CICC design concepts, which are both manufactured from a sub-cable formed by winding the REBCO tapes spirally around a stainless steel spiral tube. As part of the on-going activities to develop REBCO CICC, two sections of sub-cable specimens were manufactured and bended to U-shape for testing under magnetic fields up to 20 T. The sub-cable specimens having 30 commercial 4 mm wide REBCO tapes features around 10 kA at 4.2 K and background magnetic field up to 20 T, which also shows a stable operation under electromagnetic (EM) load of around 200 kN/m, above 150 kN/m required by the designed CICC sub-cable. However, the calculated Ic of the other specimen degraded from 8.8 kA to 8.5 kA when cycling with an EM load of around 160 kN/m. The lower calculated n-value at 77 K and self-field as well as the observed imprints on the disassembled tape edges suggested that there should be some defects 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 the HFRC sub-cable for high field fusion magnet. But winding parameters need to be optimized to make sure safe operation in a more complex condition in Tokamak, especially if using tapes same as that used for the sample-B. Moreover, much more rigorous requirements should be listed for coil manufacturing processes without producing any defect in the tapes.

Section: Rebco Tapes and Sub-cablementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Jin,

Zhou,

Fang

et al. 2023

Self Cite

“…For example, in CFETR (China Fusion Engineering Test Reactor) project and ARC (Affordable, have emerged. Such as TSTC [7][8][9], Roebel [10][11][12], QS-I [13][14][15][16][17], cable on round core (CORC) [18][19][20], etc. Among them, the CORC cable is considered to be one of the best candidates for the fusion project since it is easy to manufacture and has low inductance [21][22][23][24].…”

Section: Introductionmentioning

confidence: 99%

Bending performance of the CORC cable with flexible interlocked stainless steel former

Shi,

Ma,

Dai

et al. 2023

Self Cite

The high temperature superconducting cable on round core (CORC) is a kind of cable that could be used in fusion projects. Nevertheless, conventional copper former CORC cables require a large external force to allow the cable to endure plastic deformation and be tightly wound into solenoids. In this case, the superconducting tape will be affected by concentrated stress, resulting in a risk of critical current degradation. Therefore, this paper proposes a new CORC cable with flexible interlocked stainless steel former, which can be wound into a solenoid by applying a small external force. To verify the bending performance of this interlocked former CORC cable, a double-layer and a ten-layer interlocked stainless steel former CORC cable, as well as a double-layer traditional copper former CORC cable, are fabricated. And these three CORC cables are used to wind solenoids of various radius sizes respectively. The experimental results show that the critical bending radius of the double-layer interlocked stainless steel former CORC cable is less than 20 mm, the critical bending radius of the ten-layer interlocked stainless steel former CORC cable is less than 50 mm, and the critical bending radius of the double-layer traditional copper former CORC cable is larger than 55 mm. A self-consistent finite element model for the critical current of the CORC cable solenoid is also established. And the critical current experimental results are in good agreement with the simulation results. The results of this paper verify the excellent bending performance of the interlocked former CORC cable, which provides a good option for the preparation of insert magnets for future fusion projects.

“…For the applications of REBCO tapes, several key properties are very important, such as the critical current (I c ), yeild stress and electromechanical behaviors. Extensive work has been done to understand the behaviors of REBCO tapes and coils under different conditions, including the change of I c under different external forces and deformations [7][8][9][10][11][12][13][14][15][16], the current redistribution [17], and the behavior of current under external fields [18][19][20]. Studies showed that the I c of REBCO tapes was influenced by intrinsic strain induced by external forces or deformations [7][8][9][10][11][12][13][14][15].…”

Section: Introductionmentioning

confidence: 99%

Typical electrical, mechanical, electromechanical characteristics of copper-encapsulated REBCO tapes after processing in temperature under 250 °C

Pan

Yu³

et al. 2023

Heat treatments are inevitable not only in the production of rare earth barium copper oxide (REBCO) tapes, but also in their post-processing for applications, typically, in soldering and epoxy/wax impregnation during the fabrication of REBCO coils. In general, the heat treatment of REBCO tapes should be carried out at lower temperature for a shorter time, but the specific safe boundary of heat-treatment temperature and time for REBCO tapes is still unknown. Therefore, a comprehensive study on the typical electrical, mechanical, and electromechanical characteristics of REBCO tapes after heat treatments under temperature of 250 ℃ is necessary. This work focus on the copper-encapsulated REBCO tapes, which are more robust (while with much lower engineering current density) to be processed in application systems than the tapes without encapsulation. The critical current degradation, stress-strain characteristic, and electromechanical properties of REBCO tapes were measured after heat treatments at different temperatures in argon and oxygen atmosphere. A 2D finite element analysis model was established for detailed stress/train analyzes under tension and bending based on the analysis of residual stress/strain. The results indicate that the critical current of the copper-encapsulated REBCO tapes decreases with increasing heat-treatment temperature and dwell time, and is of no evident relation to atmosphere. In addition, increased temperature of heat treatment leads to an obvious decrease in the yield strength and critical tensile stress. This effect is mainly attributed to the degradation of mechanical properties of the encapsulated copper layer, which is demonstrated by the combination of our finite element simulation and the experiments results. Interestingly, the change in the critical bending radius due to heat treatments was slight, because the bending axial strain of the REBCO layer remained almost unchanged after heating. It is also worthy to note that all the properties tested in this study were irrelevant to the external oxygen partial pressure during the heating process. As a practical conclusion for the application systems, an upper and atmosphere-irrelevant limit of processing temperature of 130 or 150 ℃ (2 h dwell time) was proposed for copper-encapsulated REBCO tapes, under which the critical current, yield strength, critical tensile stress/strain and critical bending radius of the copper-encapsulated REBCO tapes decay by < 1% or 3%, respectively.