DE20318640U1 - Core conductor for multifilament superconductors - Google Patents

Abstract

Core conductor with an Nb or NbTa rod and a bronze matrix enveloping it, characterized in that the bronze matrix has an inner tube made of CuSnX with X = 5 to 15% by weight rest of Cu and an outer tube made of CuSnY rest of Cu with Y = 16 up to 24% by weight of the remainder is Cu.

Description

The innovation affects a core leader for multifilament superconductors, for example Multifilament high-field superconductor with a bronze composite in particular. especially multifilament high field superconductors.

The development of high-resolution nuclear magnetic resonance (NMR) spectroscopy is closely linked to the further development of technical superconductors. The operating frequency and thus the signal resolution and sensitivity of the NMR spectrometer could be increased to 800 MHz and 900 MHz (B = 21.1T) by introducing externally stabilized Nb ₃ Sn and (NbTa) ₃ Sn conductors with larger conductor cross sections and large production lengths become. NMR magnets require high spatial homogeneity and temporal stability of the magnetic field. The magnets operated in the short circuit place high demands on the constancy of the electrical and mechanical properties of the multifilament wires. The uniformity of the properties must be guaranteed over the entire length of the wire.

This problem is claimed by a core conductor for multifilament superconductors 1 solved , Refinements and developments are the subject of dependent claims.

While maintaining that with previous NMR systems usable free bore, the radii of the sections are made of metallic Superconductors enlarged. The operating Lorentz forces are proportional to the radius and cause increased mechanical stress in a changing package. These increased Tension is absorbed by conductors with improved mechanical strength. The invention is particularly suitable for a 1000 MHz NMR (B = 24T) Magnet.

Innovative Nb ₃ Sn multifilament conductors with NMR quality are manufactured using the bronze method. The expectations of producing Nb ₃ Sn multifilament conductors with NMR quality using known alternative production methods (jelly roll, internal Sn, ECN method, powder metallurgy) have so far not been met. The bronze technology allows scaling to large production units, reshaping using hot extrusion presses, high manufacturing reliability through good metallic bonding in the composite material and the production of conductors with large wire cross-sections. The high n values (I∞E ⁿ ) due to the high filament uniformity in the bronze matrix are also decisive for the NMR application in "persistent mode".

The superconducting, intermetallic Nb3Sn phase is by solid-state diffusion manufactured. The bronze is usually from 13.5% to 15% by weight Sn set. The upper critical field is alloyed of transition metals (e.g. Ta, Ti) to Nb) or 0.25 to 0.4 wt.% Ti in the bronze matrix (alloyed superconductors) and thus the area of application extended.

Through thermal activation in the course of the annealing treatment, the Sn diffuses from the bronze into the Nb and forms the Nb3Sn layer. The grain boundaries formed in the Nb3Sn are decisive for the high critical current density jc. The critical current Ic is determined by jc as well as by the current-carrying area A _Nb3Sn n (Ic = jc × A _Nb3Sn ). The growth processes and morphology of the current-carrying surface are influenced by Sn concentration, Sn diffusion, Nb diffusion, temperature, time and other parameters. The drawing deformation of an Sn concentration in the bronze above 15.6% by weight of Sn is negatively influenced by the course of the phase boundaries in the CuSn diagram (formation of δ phase). The δ phase present in the bronze matrix drastically reduces the formability and reduces the uniformity of the filament diameter over the length of the conductor. The inner cladding tube is somewhat thicker than the δ phase that occurs during annealing (annealing).

Surprisingly, it has been found that multifilament superconductors with bronze matrix with Sn content above / equal to 17% by weight and / or above / equal to 17% by weight Sn with 0.25 to 0.4% by weight Ti are readily formable, if for the A duplex tube made of CuSn13.5 or CuSn13.5Ti inside and CuSn17 or CuSn17Ti outside is used for core conductor production. Please refer 1a and 1b ,

The required bronze is made after the spray compacting process manufactured (Osprey process), the press blocks for the pipes as a single press block or compound spray block with a core made of CuSn13.5 or CuSn15Ti and outside CuSn17Ti or CuSn20Ti become. The tin content in the two-layer coating preferably has one Gradients on such that with increasing radius the tin content increases.

example 1 for core conductor production

The core conductors are manufactured using winding technology. An NbTa rod is positioned in a CuSn13.5 tube. After that the composite is pulled and positioned in the CuSn17 tube and pull again until profiling on hexagon.

Example 2 for core conductor production

The first step is extrusion of a composite pipe inside (e.g. CuSn13.5 or CuSn15Ti) and outside (e.g. B. CuSn17Ti or CuSn20Ti) and then positioning the NbTa in Composite and pulling up to the profiling.

Example 3 for core conductor production

After extrusion of the composite NbTa + CuSn13.5 + CuSn17Ti is formed by drawing the composite up to the hexagonal profile.

Claims (4)

Core conductor with an Nb or NbTa rod and a bronze matrix enveloping it, characterized in that the bronze matrix has an inner tube made of CuSnX with X = 5 to 15% by weight rest of Cu and an outer tube made of CuSnY rest of Cu with Y = 16 up to 24% by weight of the remainder is Cu. Core conductor according to claim 1, characterized by a doping of the inner and / or outer tube with 0.25-0.4 wt. Ti, or 0.4 to 0.5% by weight of Mg or Zr. Core conductor according to claim 1 or 2, characterized in that X is between 13.0 to 14% by weight. Core conductor according to claim 1, 2 or 3, characterized in that Y is between 16.0 to 18.0% by weight.