29 th September 2009 EuCARD-WP7 HFM Conductor specification and procurement Luc OBERLI CERN, TE-MSC-SCD

29 th September 2009 EuCARD-WP7 HFM Outline Introduction Specification for the HFM Nb 3 Sn strand Specification for the cable Future test plan of the Nb 3 Sn conductor Procurement plan

29 th September 2009 EuCARD-WP7 HFM Introduction (1) Why do we move from strand diameter of 1.25 mm to 1.0 mm ? The main reason is the instability problems appearing in the Nb 3 Sn magnets developed by LARP and preventing to reach the short sample value. A program has been launched by CERN by performing stability tests on strand to understand the role of few parameters on the self field instability. Tests done mainly on the RRP strand 54/61 with a strand diameter of 0.7 mm and 0.8 mm, only few tests performed on the NED strand produced by the PIT process. OST 54/61 NED PIT strand 288 sub-elements

29 th September 2009 EuCARD-WP7 HFM Introduction (2) The stability tests performed on RRP strands with high RRR (>150) have shown that the strand diameter and the value of the critical current are the most important parameters having an effect on the self field instability. B. Bordini B, L. Rossi, “Self fied instability in high J c Nb 3 Sn strands with high copper residual resistivity ratio”, IEEE Trans. Appl. Supercond. vol. 19 no. 3, pp , June 2009

29 th September 2009 EuCARD-WP7 HFM B. Bordini B, L. Rossi, “Self fied instability in high J c Nb 3 Sn strands with high copper residual resistivity ratio”, IEEE Trans. Appl. Supercond. vol. 19 no. 3, pp , June 2009 Introduction (3)

29 th September 2009 EuCARD-WP7 HFM 1 st result: The stability of the RRP strand is decreasing when increasing the strand diameter. 2 nd result: The stability of the RRP strand is decreasing with high critical current (specially true at 1.9K where Jc is very high and where heat capacity is low). For these reasons, the strand diameter for the HFM strand has been decreased to 1.0 mm to gain in self field stability in comparison to the NED strand. Introduction (4)

29 th September 2009 EuCARD-WP7 HFM Main characteristics of the Nb 3 Sn superconducting strands for HFM program Strand diameter1.000 ± mm Filament diameter (geometric) < 50.0  m Copper to non-copper volume ratio1.25 ± 0.10 Strand twist pitch24 ± 3 mm Strand twist directionright-handed screw Critical current at K > 873 A at 12 T > 437 A at 15 T n-value at 15 T and K> 30 RRR (after heat treatment)> 150 The Ic values are based on a Jc at 12 T of 2500 A/mm 2 and at 15 T of 1250 A/mm 2.

29 th September 2009 EuCARD-WP7 HFM Main characteristics of Nb 3 Sn cables for HFM program FRESCA IISMC Cable width21.4 mm10 mm Cable mid-thickness at 50 MPa1.82 mm1.81 mm Keystone angle0 degree Cable transposition pitch~ 160 mm~ 75 mm Number of superconducting strands4018 Critical current at K, with field normal to broad face A at 15 T A at 12 T 7080 A at 15 T A at 12 T Minimum critical current at K of extracted strand 393 A at 15 T 786 A at 12 T 393 A at 15 T 786 A at 12 T 15 T and K> 20 Residual resistance ratio before reaction after reaction ≥ 70 ≥ 120 ≥ 70 ≥ 120 Cable transposition directionleft-handed screw thread Packing factor83.5 %81 % Minimum unit length~ 350 m100 m

29 th September 2009 EuCARD-WP7 HFM Future test plan of the Nb3Sn conductor The following test plan is to access the self field instability of Nb 3 Sn strand having a strand diameter of 1 mm. 1. Ic stability test on the OST strand 108/ Ic cable test on the 1st SMC cable produced with the OST strand 1 mm in diameter. 3. Ic stability test on new PIT strand at 1 mm and 0.8 mm in diameter with 192 sub-elements.

29 th September 2009 EuCARD-WP7 HFM Conductor Procurement 1 st order to be placed by CERN in the coming months for 2 PIT billets already put into fabrication by Bruker EAS ~ 9 km of strand at a diameter 1 mm -> 400 m of SMC cable 2 nd order to be placed by CERN to OST to develop a 1 mm strand with 50 micrometer sub-element diameter. Procurement for the SMC program Procurement for the FRESCA II magnet to be done to Bruker EAS or to OST depending of the results of the SMC program.