The development of cutting-edge 11-12T superconducting magnets made from Nb3Sn technology is one of the major milestones for the upgrade of the Large Hadron Collider at CERN. The upgrade, called High Luminosity LHC Project, was planned in order to reach higher luminosity and discover new particles. Replacing the NbTi superconductor with the Nb3Sn makes possible to reach a practical operating magnetic field limit of up to 16 T. The superconducting coils are formed by Nb3Sn Rutherford cables with a trapezoidal cross section and composed of 40 strands. Since the superconducting phase of Nb3Sn is very brittle and it is reached after a thermal cycle, the Nb3Sn Rutherford cable needs to be wound in a coil before the thermal treatment. The cabling process is a delicate step in the production of high performing cables that need different systems to control their quality. This work aims to provide practical tools to analyse the Nb3Sn Rutherford cable production and the strands deformations due to the high aspect ratio of the Rutherford cable. Thanks to these tools it was possible to monitor the fluctuations of the mechanical tensions of the strands during cabling, localize the manufacturing defects and find the critical mechanical distortions inside the strands which cause degradation in the electrical performances. The results of the fluctuations in mechanical tensions of the strands during cabling are compared to the size variation of the lateral facets of the cable and the data related to the number of critical deformations are compared to the degradation of the electrical performances; the comparisons were performed in order to investigate a possible specific correlation. However, further measurements are foreseen to confirm the current results.
Lo sviluppo di magneti superconduttori in grado di sviluppare campi magnetici di 11-12T realizzati con tecnologia al Nb3Sn è uno dei principali traguardi per l'upgrade del Large Hadron Collider del CERN. L'upgrade, chiamato High Luminosity LHC Project, è stato progettato per ottenere un’energia più elevata e quindi ambire alla scoperta di nuove particelle. Sostituire il materiale superconduttore al NbTi con quello al Nb3Sn rende possibile il raggiungimento di campi magnetici anche fino a 16 T. Le bobine superconduttrici sono costituite da cavi Rutherford al Nb3Sn composti da 40 fili e caratterizzati da una sezione trasversale trapezoidale. Poiché la fase superconduttiva del Nb3Sn è molto fragile e si raggiunge dopo un ciclo termico, il cavo Rutherford deve essere avvolto per formare la bobina prima del trattamento. Il processo di cablaggio è un passaggio delicato nella produzione dei cavi ad alte prestazioni, che per questo necessitano di numerosi sistemi di controllo qualità. Questo lavoro mira a fornire gli strumenti per analizzare sia la produzione dei cavi Rutherford al Nb3Sn sia le deformazioni all’interno dei fili dovute all'elevato rapporto d’aspetto del cavo. Grazie a questi strumenti è stato possibile monitorare le fluttuazioni delle tensioni meccaniche dei fili durante il cablaggio, localizzare i difetti di fabbricazione e individuare le distorsioni meccaniche critiche all'interno dei fili che provocano una degradazione delle prestazioni elettriche. I risultati delle fluttuazioni delle tensioni meccaniche dei fili durante il cablaggio sono comparati con la variazione di dimensione delle facce laterali del cavo e i dati relativi al numero di deformazioni critiche sono invece paragonati alla degradazione delle prestazioni elettriche; entrambi i confronti sono stati effettuati con l’obiettivo di individuare una possibile correlazione. Tuttavia, sono previste ulteriori misure per confermare i risultati ottenuti.
Analysis of Nb3Sn Rutherford cable production and strand deformations
PEGGIANI, SONIA
2016/2017
Abstract
The development of cutting-edge 11-12T superconducting magnets made from Nb3Sn technology is one of the major milestones for the upgrade of the Large Hadron Collider at CERN. The upgrade, called High Luminosity LHC Project, was planned in order to reach higher luminosity and discover new particles. Replacing the NbTi superconductor with the Nb3Sn makes possible to reach a practical operating magnetic field limit of up to 16 T. The superconducting coils are formed by Nb3Sn Rutherford cables with a trapezoidal cross section and composed of 40 strands. Since the superconducting phase of Nb3Sn is very brittle and it is reached after a thermal cycle, the Nb3Sn Rutherford cable needs to be wound in a coil before the thermal treatment. The cabling process is a delicate step in the production of high performing cables that need different systems to control their quality. This work aims to provide practical tools to analyse the Nb3Sn Rutherford cable production and the strands deformations due to the high aspect ratio of the Rutherford cable. Thanks to these tools it was possible to monitor the fluctuations of the mechanical tensions of the strands during cabling, localize the manufacturing defects and find the critical mechanical distortions inside the strands which cause degradation in the electrical performances. The results of the fluctuations in mechanical tensions of the strands during cabling are compared to the size variation of the lateral facets of the cable and the data related to the number of critical deformations are compared to the degradation of the electrical performances; the comparisons were performed in order to investigate a possible specific correlation. However, further measurements are foreseen to confirm the current results.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/135903