EP-3861574-B1 - TECHNIQUES FOR CRYOGENIC RADIATION ENHANCEMENT OF SUPERCONDUCTORS AND RELATED SYSTEMS AND METHODS

Inventors

• SORBOM, Brandon, Nils
• HARTWIG, Zachary
• WHYTE, Dennis G.

Dates

Publication Date

20260506

Application Date

20191002

Claims (5)

1. A method comprising: irradiating a polycrystalline high temperature superconductor, HTS, tape with neutrons while the HTS tape is at a cryogenic temperature, the cryogenic temperature being between 10 K and 80 K, wherein the HTS tape has a thickness between 0.001 mm and 0.1 mm, a width between 1 mm and 12 mm, and exhibits less than 10% grain boundary misalignment, wherein the HTS tape comprises a layer of HTS and a buffer layer and is coated with at least one electrical conductor; and wherein the neutrons have a fluence of at least 1×10 15 neutrons per cm 2
2. A method according to claim 1, wherein the HTS tape comprises a rare-earth copper oxide superconductor.
3. A method according to claim 1, further comprising winding the coated tape around a chamber for fusing nuclei of a plasma.
4. A method according to claim 3, further comprising cryogenically cooling the wound tape and passing an electrical current through the tape, thereby generating a magnetic field suitable for confining the plasma in the chamber.
5. A method according to claim 4, wherein cryogenically cooling the wound tape includes cooling to a temperature of 20 K.

Description

BACKGROUND Superconductors are materials that have no electrical resistance to current (are "superconducting") below some critical temperature. For many superconductors, the critical temperature is below 30 K, such that operation of these materials in a superconducting state requires significant cooling, such as with liquid helium. High temperature superconductors ("HTS") are a class of superconductors that have a comparatively high critical temperature, such as between 50 K - 100 K. Some HTS materials, such as rare-earth barium copper oxide ("REBCO"), can be produced as long strands, leading to the possibility of using these materials to wind large bore magnets for use in fusion devices, among other applications. BEHERA D ET AL: "Irradiation-induced inter- and intra-granular modifications by 120 MeV S ions in YBa2Cu3O7 thick films", MODERN PHYSICS LETTERS B: CONDENSED MATTER PHYSICS; STATISTICAL PHYSICS AND APPLIED PHYSICS, WORLD SCIENTIFIC PUBLISHING CO. PTE. LTD, SG, vol. 15, no. 2, 30 January 2001 (2001-01-30), pages 69-80, XP009536813, discloses a method for inducing granular modification in YBCO thick films comprising producing YBCO thick films through diffusion reaction technique and irradiating the thick films with 120 MeV S ion irradiation. PROKOPEC R ET AL., "Suitability of coated conductors for fusion magnets in view of their radiation response", SUPERCONDUCTOR SCIENCE AND TECHNOLOGY, vol. 28, 014005, p. 1-8, (2015), XP020276280, and TORU AOKI ET AL., "Effect of Neutron Irradiation on High-Temperature Superconductors", IEEE TRANSACTIONS ON SUPERCONDUCTIVITY, vol. 21, no. 3, p. 3200-3202, (2011), XP011325434, disclose neutron irradiation of HTS tape. There is no disclosure of the neutron irradiation of an HTS tape being carried out at a cryogenic temperature between 10 K and 80 K. SUMMARY According to the present invention, there is provided a method according to claim 1. Advantageous features are provided in the dependent claims. The tape according to the invention irradiated with neutrons at a cryogenic temperature according to claim 1 chosen to effectively eliminate widening of boundaries of crystalline grains of the superconductor can be used in a field coil of a nuclear fusion reactor. BRIEF DESCRIPTION OF DRAWINGS Various aspects and embodiments will be described with reference to the following figures. It should be appreciated that the figures are not necessarily drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. FIG. 1 shows an illustrative crystal structure for a rare-earth barium copper oxide ("REBCO") compound;FIG. 2 shows a cross-section of the layers of an illustrative coated-conductor REBCO tape;FIG. 3 is a plot of normalized critical temperature (Tc) dependence on hole concentration for a wide variety of cuprate superconductors;FIG. 4 shows a TEM image of an illustrative YBCO superconductor;FIG. 5 shows a superconducting material and illustrates the difference between strong and weak pinning sites;FIG. 5A comprises two plots of (top) free energy density contributions from electron ordering and magnetization, and (bottom) their sum, showing that the normal-superconducting boundary is thermodynamically stable, allowing some flux penetration;FIG. 6 is a plot of critical current density Jc, at 5 T and 30 K, of samples irradiated at different temperatures to fluences of 1×1016 p/cm2 and 5×1016 p/cm2;FIG. 7 is a selection of plots illustrating irradiation temperature effect on REBCO Jc degradation due to proton irradiation at various measurement fields and temperatures;FIG. 8 is a plot of critical temperature of an irradiated superconductor versus the irradiation temperature;FIG. 9 compares measured critical current density Jc with a fit to the predicted dependence on weak pinning;FIG. 10A compares of Jc with measurement angle θ at low temperature, low fluence irradiation (80 K and 5×1015 p/cm2);FIG. 10B compares Jc with θ at low temperature, medium fluence irradiation (80 K and 1×1016 p/cm2);FIG. 10C compares Jc with θ at low temperature, high fluence irradiation (80 K and 5×1016 p/cm2);FIG. 10D compares Jc with θ at high temperature, low fluence irradiation (423 K and 5×1015 p/cm2);FIG. 10E compares Jc with θ at high temperature, medium fluence irradiation (423 K and 1×1016 p/cm2);FIG. 10F compares Jc with θ at high temperature, high fluence irradiation (423 K and 5×1016 p/cm2);FIG. 11A compares Jc with magnetic field strength B for an unirradiated control sample fitted to a power law;FIG. 11B compares Jc with B for a superconductor irradiated at 80 K to medium and high fluences, with calculated fits to a power law at each fluence;FIG. 11C compares Jc with B for a superconductor irradiated at 423 K to medium and high fluences, with calculated fits to a power law at each fluence;FIG. 12A is a plot of pinning limi