Control of the flux regime in BSCCO tapes by means of surface columnar defects.

Surface columnar defects (SCDs) are produced in high quality Ag/BSCCO tapes by irradiating them with 0.25 GeV gold ions only on a top layer up to 10% of the full volume. The ion beam is orthogonal to the tape plane. In the lo w current regime, the irreversibility lines (ILs) with the applied field ei ther parallel to the tracks or tilted are shifted towards higher fields and temperatures. Moreover, SCDs do not damage the superconducting properties when the magnetic field is applied perpendicularly to the tracks. It can be shown that, as a consequence, the IL anisotropy falls to zero (or is stron gly reduced) in a quite controllable range of magnetic fields near the dose equivalent field.