We have been developing rapid heating, quenching and transformation (RHQT) processed Nb sub(3)Al wires for next-generation accelerator magnets that require magnetic fields between 12 and 17 T. ...However, it has recently been found that the conventional Nb-matrix wire shows a rather strong magnetic instability at low fields. Taking this into consideration, we have begun developing Ta-matrix Nb sub(3)Al wires. We have fabricated a precursor wire with a Ta-matrix volume fraction of 0.8, and the mechanical properties of the RHQ-processed wire were examined. The effects of the RHQ condition and the area reduction (AR) after RHQ on the critical current density (J sub(c)) , and magnetization of the wire have also been examined. This paper describes the properties for the Ta-matrix wire in comparison with those of the Nb-matrix wire.
Recent studies of RHQ-processed Nb 3 Al wires for future accelerator magnets are presented and discussed. Test wires were prepared with different fabrication parameters, such as the Nb matrix ratio, ...RHQ current, area reduction ratio of the wire after an RHQ treatment and the 2nd heat treatment condition. Measurements of the critical current density (J c ) and n-value have been performed during the past several years. Recently, we performed the critical temperature (T c ) measurement, and the relationship between J c and T c was investigated by an RHQ treatment, a 2nd heat treatment, the Nb matrix ratio, and the area reduction effect.
Nb
3Al has advantages of better tolerance to strain/stress and a higher critical magnetic field (30
T at 4.2
K) for stoichiometric composition over Nb
3Sn. The rapid-heating, quenching and ...transformation annealing (RHQT) process enables to form a stoichiometric Nb
3Al with fine grain structures via metastable bcc supersaturated-solid-solution. As a result a large critical current density of Nb
3Al is achieved over the whole range of magnetic fields without trading off the excellent strain tolerance. A long-length of RHQ processing has been established, and a rectangular but Cu stabilized Nb
3Al strand is about be commercially available for NMR uses. Ag or Cu internal stabilization and Cu ion-plating/electroplating techniques have been also developed to enable the stabilized round wire for accelerator and fusion magnets. Successfully energized test coils that were manufactured with a wind-and-react technique have demonstrated that a long piece of Cu stabilized RHQT Nb
3Al wire is really available for practical applications.
Recent studies of RHQ-processed Nb sub(3)Al wires for future accelerator magnets are presented and discussed. Test wires were prepared with different fabrication parameters, such as the Nb matrix ...ratio, RHQ current, area reduction ratio of the wire after an RHQ treatment and the 2nd heat treatment condition. Measurements of the critical current density (J sub(c)) and n-value have been performed during the past several years. Recently, we performed the critical temperature (T sub(c)) measurement, and the relationship between J sub(c) and T sub(c) was investigated by an RHQ treatment, a 2nd heat treatment, the Nb matrix ratio, and the area reduction effect.
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