Ultrasonic investigations of vortex textures in ³HeA

Zero sound attenuation has been used to probe vortex textures in rotating 3HeA. The highly nonlinear rotation speed dependencies of the measured sound amplitudes can be explained partly as being due to sonic velocity gradients in the vortex cores. Calculations of sound propagation in the geometrical limit have been made to extract information on the types of vortex cores and their sizes using our experimental data.