Measuring method of critical current density of superconductor wires using measurement of magnetization loss

A method for measuring critical current density of superconductor wires, the method comprising:

• (a) applying an external magnetic field to the superconductor wires;
• (b) measuring a magnetization loss of the superconductor wires, according to the application of the external magnetic field;
• (c) normalizing the measured magnetization loss, and then calculating a full-penetration magnetic field of the superconductor wires according to the normalized magnetization loss;
• and
• (d) calculating a critical current density of the superconductor wires according to the calculated full-penetration magnetic field, wherein:
• at (b), a Brandt's strip model equation
• Q
• m
• =
• 2
• ⁢
• ⁢
• B
• m
• 2
• ⁢
• μ
• 0
• ⁢
• π
• ⁢
• ⁢
• ω
• 2
• ⁢
• ⁢
• β
• ⁢
• ⁢
• d
• ⁡
• [
• 2
• β
• ⁢
• ln
• ⁢
• ⁢
• (
• cosh
• ⁢
• ⁢
• β
• )
• -
• tan
• ⁢
• h
• ⁢
• ⁢
• β
• ]
• is applied to the calculation for measuring the magnetization loss of the superconductor wires, where Qm is the magnetization loss by the external magnetic field applied in a vertical direction of the superconductor wires, Bm is a dimension for the external magnetic field, ω is a frequency, β is a ratio of the external magnetic field to a characteristic magnetic field, μ0 is a vacuum permeability which is a constant value, and d is the width of the superconductor wires;
• and further wherein operation (c) comprises:
• (c1) normalizing the measured magnetization loss;
• (c2) differentiating the normalized magnetization loss;
• and
• (c3) calculating the full-penetration magnetic field by determining a relation of the characteristic magnetic field applied to Brandt's strip model equation and the full-penetration magnetic field, according to a differentiated value of the normalized magnetization loss,
• and further wherein at (c3), the relation of the characteristic magnetic field and the full-penetration magnetic field is expressed as an equation Bd=β×Bp, where Bd is the characteristic magnetic field, Bp is the full-penetration magnetic field, and β is the ratio of the external magnetic field to the characteristic magnetic field;
• and further wherein β is determined when the differentiated value of the normalized magnetization loss becomes zero at (c2).