Assembly and Mechanical Analysis of the Canted-Cosine-Theta Subscale Magnets

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A dipole magnet generating 20 T and beyond will require high-temperature superconductors such as Bi2Sr2CaCu2O8-x and REBa2Cu3O7-x (RE = rare earth, REBCO). Symmetric tape round (STAR®) wires based on REBCO tapes are emerging as a potential conductor for such a magnet, demonstrating a whole-conductor current density of 580 A mm-2 at 20 T, 4.2 K, and at a bend radius of 15 mm. There are, however, few magnet developments using STAR® wires. Here we report a subscale canted cosθ dipole magnet as an initial experiment for two purposes: to evaluate the conductor performance in a magnet conﬁguration and to start developing the magnet technology, leveraging the small bend radius aﬀorded by STAR® wires. The magnet was wound with two STAR® wires, electrically in parallel and without transposition. We tested the magnet at 77 and 4.2 K. The magnet reached a peak current of 8.9 kA, 78% of the short-sample prediction at 4.2 K, and a whole-conductor current density of 1500 A mm-2. The experiment demonstrated a minimum viable concept for dipole magnet applications using STAR® wires. The results also allowed us to identify further development needs for STAR® conductors and associated magnet technology to enable high-ﬁeld REBCO magnets.

Section: Magnet Configurationmentioning

confidence: 99%

An initial magnet experiment using high-temperature superconducting STAR® wires

Wang

Bogdanof

Ferracin

et al. 2022

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“…For assembly of the wax impregnated coils, the cure temperature is kept below 35 • C to avoid melting of the wax. The details of this assembly process can be found in [17]. The process is then repeated after inserting the two coils into an aluminum shell.…”

Section: Cct Subscale Magnetsmentioning

confidence: 99%

Training-free demonstration of a 5.4 T Nb₃Sn Canted–Cosine–Theta accelerator dipole impregnated with paraffin wax

Arbelaez,

Teyber,

Rudeiros Fernández

et al. 2024

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Lawrence Berkeley National Laboratory (LBNL) is pursuing stress-managed Nb3Sn Canted-Cosine-Theta (CCT) magnet technology for high field accelerator magnets. Although promising results have been reported, improvements in the training performance are desired. This work describes the fabrication and testing campaigns of two subscale Nb3Sn CCT magnets; a baseline impregnated with National High Magnetic Field Laboratory (NHMFL) Mix-61 and a magnet impregnated with paraffin wax. The paraffin magnet reached the short sample limit of the conductor, to within the measurement uncertainty, with no training quenches inside the magnet. In contrast, the baseline magnet reached 80% of the short sample limit after approximately 20 quenches and exhibits some loss of memory after thermal cycles. Inter-layer flexible quench antennas combined with voltage tap data show that all quenches appear identical and originate from a region corresponding to the location of peak field in the cable. Although this success should be replicated at higher fields, these first test results demonstrate the potential for training free Nb3Sn accelerator magnets operating near the short-sample limit.

“…However, one of the key challenges in Nb 3 Sn CCT magnet research involves optimizing the impregnation between cable conductor and coil mandrel to ensure that strain-sensitive Nb 3 Sn superconductor can withstand environmental stresses, including mechanical stress and thermal stress. In recent developments, various enhancement techniques, such as epoxy improvement [9,10], paraffin wax application [11,12], and the utilization of pre-stress [13], have been suggested to address the impregnation optimization. Furthermore, the use of acoustic emission has been proposed to analyze conductor motion and impregnation characteristics during training, enhancing our understanding of mechanical transients [14,15].…”

Section: Introductionmentioning

confidence: 99%

“…Furthermore, the use of acoustic emission has been proposed to analyze conductor motion and impregnation characteristics during training, enhancing our understanding of mechanical transients [14,15]. Microscopy can also be used to assess the surface condition of the impregnation both before and after magnet training, allowing for comparative analysis at room temperature [11]. Nevertheless, there is currently no technique available for directly assessing and localizing the impregnation damage during magnet cool-down, training, and operation.…”

Section: Introductionmentioning

confidence: 99%

Impregnation damage monitoring for the canted-cosine-theta magnets using time-domain reflectometry

Seok Lee,

Marchevsky,

Teyber

et al. 2024

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Impregnation plays a crucial role in the performance and protection of superconducting magnets. To investigate the impregnation status during quench training, a vector network analyzer (VNA)-based time domain reflectometry (TDR) is introduced. The proposed method and analyses focus on demonstrating their applicability within canted-cosine-theta (CCT) magnets, covering both artificially induced quenches using spot heaters and naturally occurring quenches. To verify the performance of the proposed method, VNA-based TDR is applied to CCT Subscale magnets developed in the US Magnet Development Program. The findings contribute to a deeper understanding of CCT superconducting magnet behavior and inform strategies for improving their performance.