1 / 16

Outline

Fabrication and Performance of Nb3Sn Rutherford-type Cable with Cu Added as a Separate Component 18 th Conference on Magnet Technology October 20 - 24, 2003 Mirco Coccoli. Outline. Introduction Mixed-strand Cable Manufacturing and Testing MC Power Losses Measurement

ivor-cervantes
Download Presentation

Outline

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Fabrication and Performance of Nb3Sn Rutherford-type Cable with Cu Added as a Separate Component18th Conference on Magnet TechnologyOctober 20 - 24, 2003Mirco Coccoli Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  2. Outline • Introduction • Mixed-strand Cable Manufacturing and Testing • MC Power Losses Measurement • A more general approach: Copper Added as a Separate Component • Quench Propagation Performance Simulated • Conclusions Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  3. Introduction • Foreseeing future Hadron Colliders, such as a 35km radius VLHC, it is desirable to investigate low cost (conductor) solutions • From the stand point of overall conductor cost, it is desirable to minimize the amount of copper that is co-processed with the superconductor during strand fabrication. • A possible solution is to add a copper fraction at final, ie cabling stage Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  4. MC Manufacturing • Two Mixed-strand Cables (MC) have been fabricated, winded in coils and tested • The first difficulty has been the matching of the elongation between the two types of strand, resulting in a mechanically instable cable (popped strands) Superconducting Strands Pure Copper Strands Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  5. MC Electrodynamic Study Field Sweep • P~Pc(FO) NsNs,sc - Less eddy current loops  Smaller power loss - This feature has been measured (M. D. Sumption et al, “AC Loss of Nb3Sn-based Rutherford Cables with Internally and Externally Added Cu” ASC02) on the tested cable and in agreement with the formula Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  6. Mixed Strand Test in SMTF (1) • The mechanical problem noticed during the cable fabrication have been shown by the tests performed in the Subscale Magnet Test Facility (SMTF) at Berkeley Lab • Two coils have been wounded out of Mixed Strand cables • Simple mixed strand • Mixed strand cable with SS core for mechanical stability • Results of the Power tests have not been satisfactory (40% and 70% of ss limit) leading to the conclusion that a good compaction in these coils is too difficult to achieve Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  7. Mixed Strand Test in SMTF (2) . B (T/s) • Short Sample limit reached in Nb3Sn coil • MC 1 reached ~40% ss • MC 2 reached ~70% ss Iquench/Iss • New Solution Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  8. Copper Added as a Separate Component • Add the copper as a core • Pure copper cored  poor quality • SS-Cu strip assembled in a “sandwich stile” ss-cu-ss • Most likely alternative: cu-ss-cu  good mechanical stability Ready a coil to be tested in SMTF Ready a coil to be tested in SMTF Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  9. Quench Speed Simulations: MC vs Trad • Copper Added separately as a core means no advantage for the power losses (~) • Protection  10 times faster quench • Subject to verification in magnet tests (LBNL) • No quench heaters in Future Accel Magnets? Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  10. Quench Speed Simulations: Gel • Two “wires” model • Simulated the dependence from the electrical conductance between the sc strand and the cu strip • Quench speeds in the 1km range • To be measured in a test… Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  11. Quench Speed Simulations: added copper RRR • Added copper RRR effect on quench speed • Small effect  one degree of freedom added to the cable design • High Copper RRR  better heat conduction property  lower peak temperatures • Simulations and practical test are foreseen Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  12. Quench Speed Simulations:SC strand RRR • Effects of Sc strand RRR • Good for low RRR • Of course there is a lower limit • Typical choice ~ 40  good enough for quench speed • Stability must be addressed as a next step of this study Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  13. Quench Velocity Model Normal Zone Superconducting Zone R (z) I1(z) I1(z0) Gel Gel Gel Gel Gel Gel R (z) I2(z0) I2(z) z • The current redistributes in the nearby copper passing trough the Gel  initial hot spot • The current flows in the pure copper and redistributes back to the sc strand Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  14. Conclusions • Several alternative methods for adding Cu to a Rutherford-type superconducting cable have been investigated • This cabling technique begun as a cost effective approach to conductor/cabling in view of future HEP accelerator magnets (VLHC) • The hypothesis of protection advantages related to quench propagation velocity is being investigated • The thermal conduction channel represented by the separately added fraction of copper has been measured to be a mean of stability against “external” heat/energy sources  more test needed • Good performance in actual magnet coils has not yet been demonstrated (<first half of 2004 at LBNL?) • Testing in the Subscale Magnet Test Facility is neither a trivial nor an expensive task Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  15. End Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

  16. Auxiliary Page Mirco.Coccoli@cern.ch RMScanlan@lbl.gov

More Related