Method of producing a superconductor billet

A method of producing a superconductor billet, comprising the steps of:

• providing a copper core having a longitudinal axis and an outer surface defining a plurality of longitudinally extending grooves;
• providing a plurality of copper sheets each having a first side and an oppositely facing second side;
• providing a plurality of copper arcuate segments each having a convex surface, a concave surface defining a plurality of longitudinally extending step-shaped surfaces, and a first end face and a second end face interconnecting the convex surface to the concave surface;
• providing a copper casing having an inner circumferential surface;
• providing a plurality of substantially identical cylindrical superconducting rods each having an outer circumferential surface, a first axial end, a second axial end, and a longitudinal axis;
• attaching from two to six of said sheets to said core, such that said from two to six sheets extend radially from said core and define at least one pair of adjacent sheets, with the first side of one sheet of each pair of the at least one pair circumferentially facing the second side of the second sheet of said each pair, respectively, and the second side of the one sheet of said each pair circumferentially facing the first side of the second sheet of said each pair, respectively;
• positioning one of said arcuate segments against each of said first side and said second side of each of said sheets attached to said core, respectively, such that one of said arcuate segments is positioned between every two sheets defining a pair of said at least one pair, respectively, whereby said first end face contacts said first side of one sheet of the pair, said second end face contacts said second side of the second sheet of the pair, said concave surface is spaced from and faces towards said core, and said convex surfaces define in combination an essentially continuous circle, such that a cavity is formed between every two immediately circumferentially adjacent sheets, wherein each of said cavities is defined by a combination of a portion of said outer surface of said core having some of said longitudinally extending grooves, said first side of one of said sheets attached to the core, said second side of a immediately circumferentially adjacent sheet attached to the core, and said concave surface of said arcuate segment positioned against and between the one sheet and its immediately circumferentially adjacent second sheet;
• close packing said cylindrical superconducting rods into each of said cavities, such that the longitudinal axis of each of said rods is parallel with the longitudinal axis of said core, each of said rods is supported by and in contact with at least two immediately adjacent rods, some of said rods are received within said longitudinally extending grooves and supported by said core, and other of said rods are supported individually by said longitudinally extending step-shaped surfaces, whereby a unit is formed that comprises said core, said sheets attached to said core, said arcuate segments positioned between and in contact with every two immediately cirucmferientially adjacent sheets attached to said core, and said cylindrical superconducting rods packed into said cavities;
• surrounding said unit with said copper casing, whereby the inner circumferential surface of said copper tube is in contact with the convex surface of each of said arcuate segments of said unit, and thereby forming a covered unit;
• and
• extruding said covered unit in a single extrusion step.