COLLISION CASCADES IN HTSC AS POSSIBLE PINNING CENTERS

Computer simulation was used to study the development of collision cas cades in monocrystals of YBa2Cu3O7, YBa2Cu3O6.5 and YBa2Cu3O6 which we re produced by primary knock-on atoms (PKAs) during fast particle irra diation. Oxygen deficit was found to have an effect on the development of cascades in these phases, with a lowering of oxygen deficit decrea sing cascade sizes. The type of PKA was observed to influence the geom etry of a cascade. When heavy PKAs form a cascade, the oxygen sublatti ce is practically undisturbed, with very little disorder; while with o xygen ions as the PKA, the main displacements fall within the oxygen s ubsystem. In addition, the angular dependences of the displacement thr eshold energy for yttrium and barium ions are given.