【摘要】 本文报道了当外磁场H_e较低时(H_e<4H_rm,其中H_rm是超导管的最大捕获磁场),超导管的内磁场Hi与时间及外磁场的关系可表示为H₀+B₀（lnt+1-exp（-t/τ））,式中B₀Int与磁通蠕动有关,B_c（1—exp（-t/τ））与外磁场引起的磁通扰动有关。扰动随时间很快衰减.H₀,B_O及1/ τ随外磁场增加,在H>H_rm时,这几个量增加较大。当直流外磁场He<1/2H_rm时,超导管可将其完全屏蔽,对交流场不能完全屏蔽,但其屏蔽效果仍优于最好的金属屏蔽筒。更多还原

【Abstract】 In this paper, we report the time dependence of the magnetic field inside a YBa2Cu3O7 tube, when switching on a field We outside the tube after a zero field cooling the tube into a superconducting state. In our experiment He is smaller than 4Hrm, where Hrm is the trapped field of the tube. The dependence can be expressed as Hi(t)- H0 + B0(Int + 1 - exp( -t/τ)), where H0, B0 and 1/τ are functions of He, and they keep rising when He>Hrm. We suggest that the term of Int is caused by flux lines creeping, while (1 - exp(t-τ)) results from flux lines fluctuating, which is a short time effect. The shielding effect of YBa2Cu3O7 tubes is perfect for low dc field (<Hrm/2), and better than the best normal metal for ac magnetic no-ise.更多还原