Fabrication of Long-Length ${\rm Nb}_{3}{\rm Al}$ Wire by the Metastable Solid-Solution-Strand Restacking Method

Abstract

This paper describes two subjects, both aimed at the industrialization of Nb 3 Al conductors. One is the metastable solid-solution-strand restacking method, which is expected to be a low-cost Cu-stabilization method compared with the electroplating technique. In this paper, we mainly focus on recent efforts toward long-length production. The key point here is an improvement of the contact between the Cu tube and the restacked original strands. The second subject is the first attempt at "constant voltage" control in the continuous rapid-heating and quenching operation for 300-m-class precursor wire. With constant current control, changes in the diameter of the wire lead to variations in power per unit volume, so that the processing temperature changes. With constant voltage control, changes in diameter of the wire do not lead to changes in the power per unit volume, so that the processing temperature does not change and thus the uniformity of the longitudinal performance is improved.

Applicability of Reel-to-Reel RHQ Treatments to $ \hbox{Nb}_{3}\hbox{Al}$ Precursors With a Ta/Cu/Ta Three-Layer Filament-Barrier Structure

“…In the CV mode the Joule heating voltage of the power supply (V RHQ ) was kept constant during RHQ operation; the advantages and disadvantages over the constant current (CC) mode have been discussed elsewhere [10]. To determine the optimum RHQ conditions, V RHQ was increased from 8.5 to 11.5 V at intervals of 0.5 V for a reelto-reel run of wire.…”

Development of ${\rm Nb}_{3}{\rm Al}$ Rutherford Cable for High-Field Accelerator Magnet Applications

“…In order to relax the severe control needed for the wire diameter, Banno et al recently tried a new method in which the RHQ treatment was performed under constant voltage (CV) mode instead of constant current mode [8]. Detailed analysis of this method has not yet been completed, but our impressions of this CV mode operation with respect to its ability to improve the longitudinal stability of the RHQ treatment are good.…”

Towards Development of a Next-generation High-field Nb 3 Al Superconductors

“…Example of RHQ current, voltage, diameter and input power per unit volume in constant current (CC) mode. The sample is Ta matrix wire (ME492) 15). The gap at 65 m was caused by wire breaking during the RHQ operation.…”

“…Measurement results of RHQ current, voltage, diameter and input power per unit volume in constant voltage (CV) mode. The sample is Ta matrix wire (ME530) 15). The input power per unit volume is drastically flattened in comparison to the CC mode.…”