Generation of single vortices and local detection by integrated dc SQUIDs

A test circuit for the local generation and detection of single vortices has been fabricated, based on a multilayer structure with low-pinning e-beam evaporated Nb and high-pinning reactively sputtered NbN films. The generation of vortices is performed by a current through a control line perpendicular to a low-pinning channel. For the detection and determination of the position of generated vortices, several dc SQUIDs were located around the low-pinning channel and the control line. The presence of single vortices in the channel lead to a shift in the dc SQUID flux-to-voltage transfer function. By computer simulations of the 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 /spl plusmn/1 /spl mu/m normal to and /spl plusmn/2 /spl mu/m along the channel.<>