Modélisation analytique de la puissance thermique générée par les courants de couplage à l'intérieur d'un composite supraconducteur

International audienceLorsqu'un composite supraconducteur est dans un environnement à champ magnétique variable, des courants dits de couplage sont induits. Ceux-ci, en traversant les parties résistives du composite, génèrent une puissance thermique locale. Le but de la présente contribution est de présenter un modèle permettant de calculer analytiquement et de manière précise le terme source de l'équation de la chaleur associé à cet échauffement à tout instant et en tout point de l'espace. Le modèle est ensuite appliqué à un brin réel et les résultats des simulations sont présentés et commentés

Nondestructive Analysis of Nb 3 Sn CICC and Strand by X-Ray Tomography

International audienceno abstrac

AC coupling losses in CICCs: analytical modeling at different stages

International audienceCable-in-conduit conductors (CICCs) are composed of a large number of strands (superconducting composites and copper strands) twisted together in several stages with different twist pitches. They are widely used in large fusion tokamaks such as JT-60SA or ITER. However, because of their complex transposed geometry at a strand scale, the knowledge of ac coupling losses in these conductors is limited and still has some improvement margins to capture its complexity while the prediction of their behavior under transient regimes (e.g., central solenoid) is of first importance to assess a safe operation in tokamaks. Consequently, we have carried out an in-depth theoretical generic study of a single stage of a CICC and analytically derived the expression of coupling losses using physical parameters (time constant and partial shielding coefficient) determined from electromagnetic and geometrical properties. Our approach has been inspired by the MPAS model (extensively used on the experimental ITER database) but starts from the analytical description of a single stage and aims at reaching the CICC scale in an iterative way

Development of a new generic analytical modeling of AC coupling losses in cable-in-conduit conductors

Coupling losses induced in CICCs when subject to a time-varying magnetic field are a major issue commonly encountered in large fusion tokamaks (e.g. JT-60SA, ITER, DEMO). The knowledge of these losses is crucial to determine the stability of CICCs but is yet difficult to achieve analytically (thus in a short computation time) given the specific and complex architecture of these conductors although numerical solutions such as THELMA and JACKPOT already exists. In an attempt to ease the resolution of this problem, we have previously presented a theoretical generic study of a group of elements twisted together (representing a cabling stage of a CICC) and derived the analytical expression of its coupling losses. We have now extended this study to a two cabling stage conductor by establishing an analytical model to calculate its coupling losses as function of its effective features. In a second part, we compare our results to these of THELMA and JACKPOT on geometries representing ITER CS and JT-60SA TF conductors. Finally, we have set up a specific algorithm to reconstruct strand trajectories from X-ray images and have extracted the effective geometrical parameters of a JT-60SA TF conductor

ITER Central Solenoid Insert Test Results

The ITER central solenoid (CS) is a highly stressed magnet that must provide 30 000 plasma cycles under the ITER prescribed maximum operating conditions. To verify the performance of the ITER CS conductor in conditions close to those for the ITER CS, the CS insert was built under a USA-Japan collaboration. The insert was tested in the aperture of the CSMC facility in Naka, Japan, during the first half of 2015. A magnetic field of up to 13 T and a transport current of up to 60 kA provided a wide range of parameters to characterize the conductor. The CS insert has been tested under direct and reverse charges, which allowed a wide range of strain variation and provided valuable data for characterization of the CS conductor performance at different strain levels. The CS insert test program had several important goals as follows. 1) Measure the temperature margin of the CS conductor at the relevant ITER CS operational conditions. 2) Study the effects of electromagnetic forces and strain in the cable on the CS conductor performance. 3) Study the effects of the warmup and cooldown cycles on the CS conductor performance. 4) Compare the conductor performance in the CS insert with the performance of the CS conductor in a straight hairpin configuration (hoop strain free) tested in the SULTAN facility. 5) Measure the maximum temperature rise of the cable as a result of quench. The main results of the CS insert testing are presented and discusse