Development of a Nb3Sn quadrupole magnet model

CEA, Centre d'Etudes Nucleaires de Saclay, Gif-sur-Yvette
IEEE Transactions on Applied Superconductivity (Impact Factor: 1.24). 04/2001; 11(1):2184 - 2187. DOI: 10.1109/77.920291
Source: IEEE Xplore


One possible application of Nb3Sn, whose
superconducting properties far exceed those of NbTi, is the fabrication
of short and powerful quadrupole magnets for the crowded interaction
regions of large particle accelerators. To learn about Nb3Sn
technology and to evaluate fabrication techniques, DAPNIA/STCM at
CEA/Saclay has undertaken an R&D program aimed at designing and
building a 1 m-long, 56 mm single-aperture quadrupole magnet model. The
model relies on the same coil geometry as the LHC arc quadrupole
magnets, but has no iron yoke. It is expected to produce a nominal field
gradient of 211 T/m at 11870 A. The coils are wound from Rutherford-type
cables insulated with quartz fiber tapes, before being heat-treated and
vacuum-impregnated with epoxy resin. Laminated, austenitic collars,
locked around the coil assembly by means of keys restrain the Lorentz
forces. After reviewing the conceptual design of the magnet model, we
report on the cable and cable insulation development programs and we
present the results of NbTi-Nb3Sn cable splice tests

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    • "In the case of TESLA Nb 3 Sn cables, the insulation will rely on more fragile mineral fiber tapes and may have to be thicker (DAPNIA/STCM is currently developing a quartz fiber tape that could yield a minimum of 120 µm per conductor face [6]). This over-thickness can be compensated by removing the wedge insulation and/or by reducing the conductor midthickness . "
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    ABSTRACT: One of the main issues for particle accelerator magnets is the control of interstrand resistances. Too low resistances result in large coupling currents during ramping, which distort field quality, while too large resistances may prevent current redistribution among cable strands, resulting in degraded quench performance. In this paper, we review a series of interstrand resistance and AC-loss measurements performed on four Rutherford-type cables. The four cables have the same number of strands and similar outer dimensions, corresponding to LHC quadrupole cable specifications. The first cable is made from NbTi strands, coated with silver-tin alloy, the second one is made from bare Nb<sub>3</sub>Sn strands, the third one is made also from bare Nb<sub>3 </sub>Sn strands but includes a 25-μm-thick stainless steel core between the strand layers, and the last one is made from Nb<sub>3</sub>Sn strands plated with chromium. To cross-check the two measurement types and assess their consistency, we compare the coupling-current time constants determined from AC-loss measurements with estimates based on a simple analytical model and relying on measured interstrand resistances
    IEEE Transactions on Applied Superconductivity 04/2001; 11(1-11):2760 - 2763. DOI:10.1109/77.919635 · 1.24 Impact Factor
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