GENERATION OF SINGLE VORTICES AND LOCAL DETECTION BY INTEGRATED DE SQUIDS

A test circuit for the local generation and detection of single vortic es has been fabricated, based on a multilayer structure with low-pinni ng e-beam evaporated Nb and high-pinning reactively sputtered NbN film s. The generation of vortices is performed by a current through a cont rol line perpendicular to a low-pinning channel. For the detection and determination of the position of generated vortices, several dc SQUID s were located around the low-pinning channel and the control line. Th e presence of single vortices in the channel lead to a shift in the dc SQUID flux-to-voltage transfer function. By computer simulations of t he flux that a single vortex generates at the position of the SQUIDs, the number and location of generated vortices could be determined. The spatial resolution of this procedure was determined to be about +/-1 mu m normal to and +/-2 mu m along the channel.