Long columnar defects with constant column size in 180-MeV Fe-irradiated Bi2Sr2CaCu2Ox crystals

180-MeV Fe ion beams were used to bombard the Bi(2)Sr(2)CnCu(2)O(x) single crystals. The damage morphologies dong the ion traces were investigated usi ng cross-sectional. transmission electron microscopy. Comparing with heavy- ion (Au or Pb) irradiation, the light Pc-ion irradiation shows several spec ific damage behaviors: the appearance of long columnar defects with constan t column size, the disappearance of the peak of damage efficiency, and the much lower threshold of stopping power for generating columnar defects. An effective method has been developed for qualitatively analyzing the changin g law of the damage size with the ion velocity. The applications on both Fe - and Au-irradiated Bi2Sr2CaCu2Ox crystals and the obtained results indicat e that the appearance of long columnar defects with constant column size is a specific phenomenon only occurring in light-ion irradiation. A qualitati ve analysis has been also done to prove that the threshold of stopping powe r for generating columnar defects is not a material constant but decreases as the mass of incident ion decreases, which further explains the lower thr eshold of stopping power in light Fe-ion irradiation.