摘要
1 Introduction It is very important for practical application of HTSC to increase the critical cur-rent density （J<sub>c</sub>）by artificially introducing pinning centers to enhance flux pinning.Ex-periment results show that neutron radiation is 1000 times more effective than theelectron and proton radiation.So in recent years,the neutron radiation has becomepopular,theoretically and practically.After irradiation of fast neutrons in high flux,the magnetization ratio of polycrystal samples of Y and Bi Systems are M<sub>irr</sub>/M<sub>unirr</sub>≈2.8—3.1.But T<sub>c</sub> is descending with the neutron flux increasing and the decreasingratio is about（2.6—3.0 K）/(10<sup>18</sup> n/cm<sup>2</sup>).
基金
National Centre for Research
Development of Superconductivity
Foundation for Doctoral Education of China.
