arXiv subjects

Kazuhiro Kajikawa

Publications and source records attributed to Kazuhiro Kajikawa.

4 recordsLinked to original sources

arXiv2011

A Simple Method to Eliminate Shielding Currents Generated when Magnetization is Perpendicular to Superconducting Tapes Wound into Coils

Application of an external AC magnetic field parallel to superconducting tapes helps in eliminating the magnetization caused by the shielding current induced in the flat faces of the tapes. This method helps in realizing a magnet system with high-temperature superconducting tapes for magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) applications. The effectiveness of the proposed method is validated by numerical calculations carried out using the finite-element method and experiments performed using a commercially available superconducting tape. The field uniformity expected for practical applications is estimated to be less than 1 ppm.

cond-mat.supr-con↗

arXiv2007

Hysteretic ac loss of polygonally arranged superconducting strips carrying ac transport current

The hysteretic ac loss of a current-carrying conductor in which multiple superconducting strips are polygonally arranged around a cylindrical former is theoretically investigated as a model of superconducting cables. Using the critical state model, we analytically derive the ac loss $Q_n$ of a total of $n$ strips. The normalized loss $Q_n/Q_1$ is determined by the number of strips $n$ and the ratio of the strip width $2w$ to the diameter $2R$ of the cylindrical former. When $n>> 1$ and $w/R<< 1$, the behavior of $Q_n$ is similar to that of an infinite array of coplanar strips.

cond-mat.supr-con↗

arXiv2006

Hysteretic ac loss of superconducting strips simultaneously exposed to ac transport current and phase-different ac magnetic field

A simple analytical expression is presented for hysteretic ac loss $Q$ of a superconducting strip simultaneously exposed to an ac transport current $I_0\cosωt$ and a phase-different ac magnetic field $H_0\cos(ωt+θ_0)$. On the basis of Bean's critical state model, we calculate $Q$ for small current amplitude $I_0\ll I_c$, for small magnetic field amplitude $H_0\ll I_c/2πa$, and for arbitrary phase difference $θ_0$, where $I_c$ is the critical current and $2a$ is the width of the strip. The resulting expression for $Q=Q(I_0,H_0,θ_0)$ is a simple biquadratic function of both $I_0$ and $H_0$, and $Q$ becomes maximum (minimum) when $θ_0=0$ or $π$ ($θ_0=π/2$).

cond-mat.supr-con↗

arXiv2006

Alternating current loss in radially arranged superconducting strips

Analytic expressions for alternating current (ac) loss in radially arranged superconducting strips are presented. We adopt the weight-function approach to obtain the field distributions in the critical state model, and we have developed an analytic method to calculate hysteretic ac loss in superconducting strips for small-current amplitude. We present the dependence of the ac loss in radial strips upon the configuration of the strips and upon the number of strips. The results show that behavior of the ac loss of radial strips carrying bidirectional currents differs significantly from that carrying unidirectional currents.

cond-mat.supr-con↗