Performance of Nb$_{3}$Sn RRP Strands and Cables Based on a 108/127 Stack Design

Abstract

Abstract-The high performance Nb 3 Sn strand produced by Oxford Superconducting Technology (OST) with the Restack Rod Process (RRP) is presently considered as a baseline conductor for the Fermilab's accelerator magnet R&D program. To improve the strand stability in the current and field range expected in magnet models, the number of subelements in the strand was increased by a factor of two (from 54 to 108), which resulted in a smaller effective filament size. The performance of the 1.0 and 0.7 mm strands of this design was studied using virgin and deformed strand samples. 27-strand Rutherford cables made of 1 mm strand were also tested using a superconducting transformer, small racetrack and 1-m shell-type dipole coils. This paper presents the RRP strand and cable parameters, and reports the results of strand, cable and coil testing.

NB₃SN accelerator magnet technology R&D at Fermilab

“…The MJR strand had higher critical current density J c (12T, 4.2K)~2-2.2 kA/mm 2 and larger filament size d eff~1 00-110 μm whereas PIT strand had lower J c~1 .6-1.8 kA/mm 2 and smaller d eff~5 0-60 μm [2]. A new improved strand based on Restack Rod Process (RRP) was recently developed by Oxford Superconductor Technologies [3]. This strand provides highest Jc (<3 kA/mm 2 ) and has a larger number of sub-elements with smaller size (~70 μm).…”

“…The scale-up is performed in two steps starting with a 2-m long coil made of PIT Nb 3 Sn strand which has demonstrated the good stability and reproducible performance. This will be followed by 4-m long coil dipole mirror models were fabricated and tested at Fermilab.…”

“…de of advanced RRP Nb 3 Sn strand [3]. Reference 1-m long coils made of PIT and RRP st were fabricated and tested in the mirror configur The mirror model with a 2-m long PIT coil was al fabricated (Fig.…”

“…Nb 3 Sn accelerator magnets allow magnet operation above 10 T and drastically increase the coil temperature margin relative to NbTi magnets. Magnets with such parameters are needed for the LHC IR upgrade, cr mponents of ILC, MSR and MC magnet systems.…”

TESTING OF NB[sub 3]SN QUADRUPOLE COILS USING MAGNETIC MIRROR STRUCTURE

“…The results of these studies are reported elsewhere [10]. The third mirror model TQM03 was assembled with a new TQ coil made of improved Nb 3 Sn RRP strand of 108/127 design [11] with more spaced subelements [12]. The cable for this coil was fabricated using Fermilab's cabling machine [13] and insulated with E-glass tape using standard cable insulating technique.…”