HIGH-Q OSCILLATOR MEASUREMENTS OF VORTEX PROPERTIES IN YBA2CU3O7-DELTA

High-Q oscillators, vibrating with extremely small tilt angles, simila r to 10(-7) radians, were used to study vortex behavior in single crys tal YBa2Cu3O7-delta. Systematic changes in the dissipation and frequen cy of the oscillator were explored for various fields both parallel an d perpendicular to twin boundaries. At the small tilt oscillation ampl itudes employed here, a number of features were observed which are not evident at the more typically utilized large oscillation amplitudes.