Magnetic shielding and harmonic generation in high-T_c superconducting tubes

Magnetic shielding and harmonic generation in a sintered Y₁Ba₂Cu₃O_7-x tube, subjected to an incident AC magnetic field, has been studied. This study has shown that the onset of superconductivity in the specimen introduces a magnetic shielding of about 25 dB. Odd harmonics are generated during the propagation of the AC magnetic field. Flux trapping occurs in the specimen for frequencies less than 10 kHz. This trapped flux behaves as a superimposed DC magnetic field and results in a low shielding effectiveness and generation of even harmonics in the transmitted waveform.